Hamilton Journal-News

Q: My wife’s 1992 Nissan Maxima with a V-6 engine and 108,000 miles starts and runs fine. The trouble is that after she starts the engine she smells gasoline even after the engine warms up. Do you have any idea what’s wrong? R.B., e-mail

A: The fuel odor is likely caused by a gasoline leak. There is danger the vehicle might catch on fire. Do not operate the vehicle until the trouble is fixed.

Some older model Maximas were recalled for fuel tank leaks and fuel injection hose leaks. Your wife’s car might be subject to a recall. Call your local dealer to explain the trouble and make an appointment to have the fuel leak repaired.

To prevent the possibility of the vehicle catching on fire, tow the car to a repair shop.

Pot hole causes elusive noise

Q: Months ago I was driving my 1992 Oldsmobile Cutlass Ciera with 165,000 miles when the right front tire hit a fairly large hole. Since then I have been hearing a noise from the right front of the car. The noise is similar to what I hear when driving over railroad tracks. It also feels like the right front tire is bouncing as I drive along.

I took the car to two different mechanics. The tires have been replaced and the wheels have been aligned. Despite this the noise continues. Both mechanics have visually inspected the car. Neither mechanic has found anything wrong.

Is it dangerous to drive the car? Is it repairable? Should I abandon the vehicle? A.R., Wetumpka, Ala.

A: Until the source of the noise is found and repaired there is potential for a failure that can cause an accident. The car can be repaired but since it is a 1992 model the cost of repair may exceed the value of the vehicle. However, if the car is in good overall condition and it has received proper and regular preventive maintenance all these years it certainly will cost less to repair the problem than to purchase a new car.

Since you feel that the tire bounces it is possible that the axle on the right wheel is bent. It’s rare but a technician should check the axle and wheel run-out to determine if this is the case. The bearings at the right wheel may also be damaged. Suspension arms, strut, stabilizer bar and bushings at attachment points should be thoroughly inspected. Also, if your car is equipped with hubcaps a bent cap could cause noise and cause a tire to be out of balance.

Since the noise is loud an experienced technician should at the very least test drive the car. A test drive can provide valuable information such if the noise seems to coincide with wheel rotation and speed or if it only occurs when the suspension moves. This is an important step in pinpointing the cause. Once this is accomplished a visual inspection along with measurements should lead to a proper and lasting repair.

Incidentally, repairs might be covered by your insurance company. Also, since the problem was caused by a hole in the road, the county or city government might be liable for some or all of the cost of repair. Up here in the north where potholes can become caverns cities such as Chicago have picked up the tab for car repairs that resulted from hitting a hole.

Poor connection hampers rear wiper

Q: Sometimes the rear wiper in my 2000 Ford Expedition quits working. When it stops it might start again. I suspect that there is a loose connection. What’s your opinion? R.W., e-mail

A: There might be a loose connection. Check the connections at the wiper motor and junction block in the engine compartment. Repair if needed as necessary.

It’s also possible that the rear wiper is malfunctioning as a result of a fault in the battery saver relay, wiper relay, generic electronic module or rear wiper switch. If you have the expertise, tools, wiring schematics and test equipment to troubleshoot the system tackle the job. If not, explain the symptoms to your favorite technician so he can diagnose the trouble.

Filled to the brim

Q: I’m the proud owner of a 1981 Jeep CJ with a carbureted engine. Recently the engine filled with gasoline. There is so much gasoline in the engine it is coming out of the air filter housing. Obviously with this condition I feel it is dangerous to start the engine.

I took the vehicle to a local mechanic. He diagnosed the trouble as a faulty carburetor. He wants to rebuild it. Could there be another reason for this? J.C.H., e-mail

A: You are correct. This indeed is a dangerous condition in more ways than one. First of all the gasoline could cause a fire. Also, with all the gas that’s in the oil it can’t properly lubricate the moving parts of the engine. This can severely damage the engine.

It appears that the mechanic made a proper diagnosis. The trouble likely is caused by a faulty float and needle and seat assembly in the fuel bowl of the carburetor. The rubber parts in the carburetor likely have deteriorated. When this occurs gasoline can leak into the engine until it is full to the brim.

Also, before operating the vehicle be sure the engine lubrication system is completely flushed of all gasoline contaminated oil. It’s important to remove all of the gasoline from the system so the oil can properly lubricate bearings and other important parts so the engine does not suffer damage from a lack of lubrication. To flush the engine, consider changing the oil and filter three times before leaving the shop. Between each change run the engine for five minutes or so to allow the oil to circulate and absorb residual gasoline in the engine. Once this is accomplished change the oil and filter after a few hundred miles of travel.

Q: Please explain how traction control works. If I keep it turned off, and only activate it when road conditions are slippery, will my gas mileage improve? G.F., Carlisle, Pa.

A: Since I don’t know the make, model and year of your vehicle, I can’t be more specific, but apparently you have the capability to turn off the system. This feature is common in many vehicles with traction control.

Basically, the traction control system utilizes a computer and sensors to monitor wheel speed. It also utilizes the antilock brake system. When the computer senses that a wheel is turning faster than other wheels, the brake on that wheel is pumped to prevent it from spinning. In doing so, traction increases. Also, many systems slow down the engine to reduce wheel spin.

As for fuel economy, anytime the wheels are spinning and the car isn’t going the speed of the wheel, fuel consumption goes up and the miles driven per gallon go down. Consider leaving the traction system on all the time. The system doesn’t consume fuel when active. When needed, it automatically turns on to prevent wheels from slipping.

Intermittent instrument panel woes

Q: A month ago the gauges in my 2002 Chevrolet Avalanche with 57,000 miles quit working. The speedometer and all gauges went to zero as I was driving along at 70 mph. The trouble continued until I stopped and restarted the vehicle. Since then the gauges have not been providing the proper information. Sometimes the gas gauge reads empty when it’s full. The tachometer isn’t providing proper engine speed and the oil gauge may read zero.

I took my truck to the selling dealer where I was told that the instrument panel might be faulty, but a technician couldn’t check it while it is functioning.

I have an extended warranty policy that covers the vehicle to 100,000 miles or April of 2007. I believe the instrument panel is covered by the policy. How can I find out if the instrument panel is faulty when the trouble is intermittent? A.A.B., e-mail

A: From what you describe, the trouble isn’t as intermittent as it could be. The indicators appear to be offering incorrect information most of the time. In a way this is good as there is a better chance a technician will find the source of the trouble.

It is possible the instrument panel is at the root of the trouble but there might be a problem in a computer module. It’s also possible that a ground connection to the cluster or a wiring harness plug has a loose connection.

Since the trouble appears to occur frequently, leave the truck at your favorite repair shop for a few days. This will give a technician an opportunity to drive the vehicle and experience the trouble. When the trouble occurs he can follow factory test procedures to track down the source of the malfunction. Testing involves several factory recommended steps with the use of a specialized scan tool that performs tests of the instrument panel circuits and modules. If tests find a fault in the wiring he can track down a fault with test equipment and the use of wiring schematics. Also, visual inspection of wiring based upon a schematic shows a technician where to inspect for problems such as loose connections.

Vapors illuminate service engine light

Q: The service engine light turns on and off in my 1998 Mazda B3000 with a V-6 engine. About a year ago, the same thing happened and a technician diagnosed the trouble as a faulty gas cap. A few months after replacing the cap, the light began to turn on and off.

I only drive the truck a couple of miles to and from work each day. The other day I drove the truck on the expressway and the service engine light turned off, but more recently it turned back on. The truck only has 36,000 miles on it. Should I worry about the light? Is it possible that the fuel tank is building up condensation? B.J., Portland, Ore.

A: It is possible condensation is building up in the fuel tank but it’s not likely caused by a faulty gas cap or the service engine light. A technician can test the gas for water content. If there is excessive water in the tank, it should be drained and cleaned, but since you did not mention any symptoms that are associated with excessive water in the gas tank, it’s not likely this is the problem.

To find out why the service engine light is illuminating, a technician should perform a computer check to read diagnostic trouble codes that might be stored in the computer memory. If codes are present, he can determine the cause and perform a proper repair. One code may pop up telling him that the gas cap is faulty. It’s possible the light is turning on as a result of a leak somewhere.

in the fuel vapor recovery system. A leak can be difficult to find. However, if you fill the gas tank with the engine running you could be triggering the light. If this is the case, make sure to turn off the ignition switch when filling the tank. Also, make sure that you snug up the cap when you are finished.

Worn bushing impairs transmission

Q: When placing the shift lever into Drive in my 2000 Subaru Outback Wagon with 130,000 miles the transmission may not engage. Sometimes it engages right way and at other times I may have to wait as long as ten minutes.

The transmission had the same problem when the car had 50,000 miles on it. A dealer technician flushed the transmission and the trouble was gone. I took the car to a dealer a couple of weeks ago but a flush did not cure the trouble. I think this problem is serious. What are your thoughts? B.L., Richmond, Va.

A: From what you describe the transmission has an internal hydraulic leak that causes hydraulic pressure loss. This might be due to an excessively worn hydraulic pump, leaky seal or excessively worn bushing. If this is true, replacement of the worn part should cure the trouble.

It’s also possible a valve is sticking. This kind of problem misdirects hydraulic fluid pressure that is necessary to the clutches that engage the forward gears. Sometimes servicing the transmission fluid and filter cures this but apparently in your case it has not. This might be a sign that the bore a valve slides back and forth in is excessively worn or a flush failed to sufficiently clean the bore and valve to return normal function. If excessive wear is the cause replacement is the cure. If not, another flush might do the trick.

It’s also possible there is an electronic problem. Perhaps an electrical connection is corroded or loose. It’s also possible a speed sensor, transmission control module, throttle position sensor, torque converter speed sensor or maybe an inhibitor switch has a fault. Tests performed by an experienced technician should find a fault in any of these electrical parts. If there is a fault replacement should cure the trouble. However, if bushings or seals are the source of the trouble the transmission will need removal and repair may mean a complete overhaul.

Sprung springs

Q: The right front coil spring in my 1998 Ford Contour broke. To fix the trouble both front springs and the struts were replaced. Now the front of the car is higher than the rear. When I asked shop personnel about the difference I was told to drive the car a few thousand miles so the springs relax. I did and the front is still higher than the rear.

I took the car to another repair shop where a mechanic checked over the work of the other shop. He says everything is fine.

I think the repair shop installed springs that are meant for a car with an 8-cylinder engine which would weigh more but the repair shop insists that the springs are correct. Can you help? K.L., e-mail

A: Over time the springs lose resistance and the car squats lower to the ground and they can break. As you have learned installation of new springs raises a vehicle. The rear springs are old and worn so the rear sags and the front is higher.

To solve this dilemma it’s likely that replacing the rear springs will raise the rear and lower the front to a proper carrying height.

Broken rod caused by poor lubrication

Q: I know you’re busy so I’ll keep this brief. Can a connecting rod be damaged due to a lack of oil? What other factors can lead to failure of a connecting rod? N.A., e-mail

A: A connecting rod in your car’s engine must have failed. Yes a connecting rod can fail due to the lack of oil. This is a common failure. Actually the bearing that connects the rod to the crankshaft fails as a result of low oil pressure due to excessive sludge deposits in the lubrication system, low oil level or perhaps an oil pump failure. When a rod bearing fails the connecting rod becomes damaged. Also, under these conditions the piston at the top of the connecting rod often seizes within the cylinder. This often causes the connecting rod to bend and break.

There also are other causes for a rod to break.

Sometimes they snap as a result of over revving the engine.

Also, they can bend and break as a result of a hydro-lock condition. Occasionally, a cylinder fills with fluid. Fluids such as gasoline and ntifreeze can create this condition. These circumstances are created as a result of a failed fuel injector or perhaps a failed cylinder head gasket.

Driving a vehicle into a puddle can cause hydro-lock, too. When driving through a puddle an engine can ingest a large amount of water. When this happens a piston can’t move up in a cylinder and the connecting rod bends and sometimes breaks.

In addition to all of this, heavy deposits of carbon or timing belt failure can lead to a broken piston and broken connecting rod. An experienced technician should be able to take into account the conditions in the engine to determine why a rod failed.

Urban legend continues

Q: The other day a fellow told me that a full fuel tank produces better gas mileage than a tank that is half full. I have never heard of this before. I suppose this fellow smokes funny cigarettes or is not playing with a full deck of cards.

Have you ever heard of this? What are your thoughts? A.R.B., e-mailA: For years there has been a story circulating that a man purchased a used vehicle that for some mysterious reason would not travel as far on a tank of gas as stated by the carmaker. Also, the gas tank would not hold the carmaker’s advertised capacity. As a result the new vehicle owner had the gas tank removed to find the source of the problem. A mechanic drained the fuel from the tank but to his surprise the empty tank weighed much more than he anticipated. Upon his examination he found half a tank full of coins inside. As the story goes apparently the previous owner placed his change in the gas tank each time he filled up with gas and this is why the car would not travel as far as compared to similar models.

The fellow who told you to keep the tank full is not completely off his rocker. There are conditions such as phase separation of the fuel, accumulations of dirt and other factors that can cause fuel to be foul at the bottom of a tank and normal at the top of the tank. As this may be it is possible for a vehicle to experience a decline in fuel economy as a gas gauge drops toward empty. However, if the tank is carrying a normal supply of fuel there should not be a decline in fuel economy as the fuel is consumed. If your vehicle experiences a loss f fuel economy or engine performance perhaps the trouble is contamination in the fuel tank.

Clutch slows vehicle acceleration

Q: My girlfriend has a 1998 Toyota Camry with a 4-cylinder engine and manual transmission. The problem is that when she accelerates the engine RPMs go up but the car does not accelerate.

In an attempt to fix the trouble I replaced the spark plugs. Now the engine runs better but the car still doesn’t accelerate as it should. What’s your advice? M.H., e-mail

A: The trouble might be that the clutch is slipping. Have this checked as soon as possible. The car will not move if the clutch burns and fails. This could occur far from home and leave your friend stranded.

This could be caused by an adjustment, excessively worn clutch or failed pressure plate. If this is fact, adjustment or replacement of an excessively worn clutch disc should solve the trouble. Also, when the clutch is replaced the pressure plate and throw-out bearing should be replaced. If the engine flywheel is damaged from heat it may need machining or it may need replacement, too.

Critters look for warmth

Q: The other day I turned on the defroster in my 1999 Ford Ranger with a 6-cylinder engine. It worked fine but there was an odor similar to a transistor burning. The odor disappeared after a few minutes. Then I told my wife it smells like a dead mouse but she disagreed. What do you think it could be? J.G., Kill Devil, NC

A: Since the air conditioning, heating and ventilation system seems to be working fine the odor more than likely is not the result of an electrical failure. During this time of year little critters look for a place to keep warm. What you detect could be a dead rodent a system duct. Look under the hood for signs of a rodent such as seeds, a nest and fur. Also, bits of a nest might blow from the dash vents. If you find items such as these it’s likely a little critter made his way into the heating and air conditioning system. If so he may have made a nest near the blower motor. Removing the motor should give you access to the duct and you might find the little guy taking an eternal nap.

Technician suggests proper repair

Q: The dash air bag warning light in my 2001 Chrysler Sebring with 38,000 miles is on and a chime sounds. I took the car to my dealer where I was told that a clock spring needs replacement. A service person told me it will cost $285 to repair which I thought is a lot of money. Is there a way to turn off the chime? G.M., e-mail

A: It’s likely that the technician who examined the vehicle did a proper diagnosis. The clock spring is in the steering column under the steering wheel. When this part breaks the air bag computer turns on the light and sounds a chime to alert you to the problem. It also deactivates the air bag system. As a result if you should have a collision the air bags will not deploy and possibly save your life.

Since this is an issue of your safety I can only suggest that you have the trouble repaired.

Low oil pressure might be problem

Q: My 1998 Honda Civic 4-door with 115,000 miles has been maintained according to factory recommendations for my area here in Minnesota. Lately once in a while after I start the engine it runs rough and hesitates as I begin to drive. Also, the engine idle drops very low but it doesn’t stall. This lasts about 30 seconds. After this brief time it runs fine.

I thought the trouble was caused by the gasoline but after burning several tanks the trouble persisted. As a result I took the car to my local dealer where a technician adjusted the valves and cruise control cable. He also tested the fuel to find it is okay. All this work was in vain and cost $300.

He also said that the fuel injectors might need replacement but this will cost $800. Also, I don’t think this is the problem as I believe that a fuel injector problem would not last only 30 seconds.

Except for this brief problem, the engine starts without a problem and runs fine. What else could cause this? T.R., e-mail

A: It’s likely that the fuel injectors are fine so don’t spend $800 just yet. Solving the trouble might be as simple as thoroughly cleaning the battery cables inside and out. The engine computer learns how you drive. Poor battery connections can scramble the computer memory. Sparkling clean battery connections inside and out might cure the condition. Also, don’t forget that during this time of year the battery is low due to cold ambient temperatures so anything that reduces electrical supply such as poor battery connections can cause weird symptoms.

Also, it’s possible that the trouble is caused by low oil pressure. There is an oil pressure sensor that sends pressure information to the engine computer. If the computer receives a low oil pressure signal it could temporarily cut fuel delivery to the engine.

During this time of year cold engine oil doesn’t flow until it warms up. Make sure the oil level is proper, fresh and clean. Also, it wouldn’t hurt to have a technician test the oil pressure to make sure that the oil pump is doing a proper job. If the pump is okay, and pressure is within factory specifications, consider using a light-weight oil suggested by the carmaker. Better yet pour synthetic oil into the engine. This will solve any oil flow problems that can occur with conventional mineral oil.

Misdirected heat

Q: Heated air doesn’t blow from the floor vents in my 1993 GMC truck. The heat only blows from the dash vents. Someone told me that this is caused by a switch on the door that blows the heat. I’m confused about this. Can you help? C.T., e-mail

A: What you were told might be true. There are small doors similar to flaps on an airplane in the heating system ducts that direct air from the heater, air conditioner and outside air. If an actuator on a door fails the door won’t move into position to direct air to the center dash vents, defroster or floor. Also, if an actuator fails you may not be able to adjust the temperature.

The doors in your vehicle likely are controlled by vacuum operated actuators. If a vacuum line has cracked or come off an actuator it will fail to move the corresponding door. A technician should check for broken vacuum lines under the hood and in the cabin under the dash. Also, a broken vacuum reservoir tank under hood could cause a condition such as you describe. He should replace parts as needed.

It’s also possible that the dash switch has failed due to excessive wear. If this is the case, replacement is the cure, but there are several vacuum lines on the switch so they should be checked for faults before replacing the switch.

Broken axle not technician’s fault

Q: I drive a 2002 Ford Windstar with 61,000 miles. Last August a front wheel bearing failed. I took the van to a local independent repair shop for repair. During the process of replacing the bearing a technician installed a nut on the axle and walked away to get another part. When he returned the axle was found on the ground. Upon examination of the axle he advised that the metal appeared to be defective.

I showed the axle to a Ford dealer representative. I was told that the technician at the independent shop must have really beaten on the axle to break it as it did. I also contacted Ford Motor Company but they didn’t offer any help.

Enclosed are pictures of the axle. Can you provide an opinion? D.C.C., Rosemount, Minn.

A: I’m not an engineer who specializes in metallurgy but from what I see in the photos it appears to be a long term defect that was waiting for failure. For a technician to break an axle he would have to be a strong as the Incredible Hulk. So far I have not met a technician with such strength.

If what you seek is to sue Ford Motor Com. to recover the repair costs you will need to hire an attorney and engineer who specializes in metal fatigue. This will cost a lot more than the repair.

What you might consider is contacting the National Highway Traffic Safety Administration to file a complaint. If an investigation develops they may want to study the axle. This might lead to a recall.

Annoying clunk mystifies repair personnel

Q: About a year and half ago I purchased a 2003 Chrysler Sebring. It now has 25,000 miles on it. Three months ago I began to hear a clunk sound that seems to come from the left front side. I don’t hear the sound every time I drive the car and I may not hear it until I drive 10 miles.

I took the car to my selling dealer where they kept it for three days, but a mechanic couldn’t find any problems. I drove the car another month and returned to the shop where a mechanic couldn’t find anything wrong after a week of probing. I was told everything under the car is tight and there should be no safety issues. It was suggested that I return when the trouble becomes worse.

The warranty will expire soon and I want this problem resolved. What do you suggest? S.H., St. Paul, Minn.

A: The trouble is that a technician needs to hear the sound before he can diagnose the cause. It appears that he never heard it and checked the suspension and other parts for security to make sure nothing is falling off.

Since tracking down the source of the sound might be up to you consider these suggestions. Sounds often travel through the body. Something in the rear might make a noise that seems as though it is in the front. Some Sebrings develop a clunk in the rear brakes when hitting a bump. Other Sebrings make a rattle or clunk sound in the front “A” pillar. The “A” pillar is the upright sheet metal post between the front door and windshield. Also, some Sebrings develop a rattle or clunk in the doors. Other Sebrings develop a rattle in the dash by the compact disc player.

If you listen to these areas you may be able to direct a technician to the source of the noise. Then he can make the appropriate adjustments by following factory technical service bulletin procedures to resolve your concerns.

Cruise control and speedometer on vacation

Q: The cruise control in my 1998 Ford Windstar with a 3.8 liter engine quit working and then started working again. Three months later the speedometer quit.

I replaced the speedometer but this didn’t cure the trouble. I have checked all the connections. I installed a new ground and replaced the speed sensor. All the other gauges are working fine. Can you help? F.G., Wausaukee, Wis.

A: If you have a repair manual, electromechanical prowess and the tools and equipment to troubleshoot the system you should be able to repair the trouble. Your vehicle likely has self diagnostic capabilities. This procedure is outlined in repair manuals. Once you perform the test you should receive diagnostic trouble codes that will lead you to a failed part or circuit. A repair manual will decode the trouble codes so you know what step to take next. The procedure will help eliminate guesswork.

The cruise control or speedometer may be suffering from a failed relay, actuator, activation switch, stop light switch, servo, cable or perhaps the linkage needs adjustment. What needs repair or replacement all depends upon what is found during a diagnostic test.

Transmission trouble deep within

Q: The automatic transmission in my 1992 Honda Accord shifts hard and shutters when it goes into second gear. I can control the shuddering by letting off the gas pedal just before the transmission shifts. I have replaced all the motor mounts but the trouble continues. Do you have suggestions? M.W., e-mail

A: The trouble is inside the transmission. This could be caused by an excessively worn seal or bushing. It’s also possible that a valve is sticking causing hydraulic pressure not to be within factory specifications.

Hydraulic and electrical tests will determine what needs repair. It’s likely that in this case the trouble will end in disassembly of the transmission, but once a technician test drives the vehicle and performs tests he may determine an adjustment will cure the trouble. Let’s hope so.

Fuel economy may not increase with aftermarket accessory

Q: I own a pickup truck. I want to increase fuel economy. I’m thinking about purchasing a soft or hard cover for the bed or lowering the tailgate.

How much gas will I save? Will lowering the tailgate save as much as a cover? M.H., Norfork, Ark.

A: Placing a cover over the cargo bed or lowering the gate may not increase fuel economy at all. I have not read any independent studies or know if in fact any studies have been performed that provide fuel consumption data with a cover over the bed or the tailgate down. However, if you study the design shape of a pickup air flow over the roof should curl behind the rear glass. This might provide a little push which in theory might improve fuel economy. Also, air flow might become trapped at the tailgate and some should curl behind the tailgate. The result might not be any gain or loss of fuel economy.

On the other hand, if there is a cover over the bed air flow might continue to provide a bit of a forward push behind the cab. Also, air will not become trapped in front of the tailgate but likely will continue to provide a bit of a push behind the gate. The result might be a slight gain in fuel economy, but then the increase in gross vehicle weight of the cover might offset any fuel economy gain because the engine has to move the additional weight.

Consider this make sure the truck is in top running condition with fresh oil, clean air filter, finely tuned engine, proper tire inflation, a fresh supply of engine coolant and properly functioning thermostat. Then drive sensibly and keep track of the fuel economy. After a few tanks of gas lower the tailgate and begin another test to see if fuel economy increases or decreases. If it increases leave the gate down especially on the highway when air resistance is greatest and latch it when you’re tooling around town.

Speedometer out of calibration

Q: I have a 1991 Ford Explorer with 139,000 miles that gets about 20 miles per gallon. It also has a 5-speed manual transmission without overdrive. I am very conscious of the tachometer. I monitor miles per hour and engine revolutions per minute. On real cold days 2000 rpms equals 70 mph. As the engine temperature reaches operating temperature 2000 rpm and the speed drops to 63 mph. In the summer the speed drops even more. 2000 rpm produces 60 mph.

I thought the clutch was slipping so I’ve replaced it twice but this didn’t solve my dilemma. Despite the difference in speed and rpm the fuel economy remains about 20 miles per gallon. What’s up? J.F., e-mail

A: This indeed is odd. Despite this it appears the clutch is operating just fine. If it wasn’t it would be slipping and it wouldn’t be too far down the road it would burn up and leave you stranded. It appears there is something amiss in the speedometer. The cable might need lubrication or perhaps a gear in the transmission is excessive worn. Also, after all these years it’s feasible the speedometer has lost calibration or maybe you routinely change tire sizes from summer to winter.

To find out if indeed there is something wrong in the speedometer a technician should perform tests. Or, you could ask a friendly cop to zap your truck with a radar gun to find out if there is a problem in the speedometer. If there is you can have it corrected at your favorite repair shop.

Fickle fuel gauge

Q: When the fuel gauge in my 2001 Ford Ranger with a 3.0-liter V-6 engine reads half full the gas tank only takes five gallons of gas. According to my owner’s guide the fuel tank capacity is 16 gallons.

To fix the trouble I replaced the fuel pump to no avail. Can you help? B.D., Grand Island, Neb.

A: This indeed is a problem because you could think the gas tank has a huge reserve so you don’t have to fill up when the gauge reads empty. You could run out of gas way out in the boonies!

The gas tank in your vehicle actually has a 16.5 gallon capacity, but the fact that your gauge says the tank is half full when only five gallons have been consumed is not unusual. What we call a gauge really isn’t a gauge, it’s an indicator. As such it isn’t as accurate as a gauge. Be this as it may it is possible the new fuel pump assembly is not the correct one for your vehicle. It’s also possible the part that was installed is not an updated unit that is supposed to cure such discrepancies. On top of all this it’s possible the dash unit has a fault. It’s very unlikely that the wrong fuel tank is in your truck but it sure wouldn’t hurt to check as I have seen this problem in the past.

Ask a technician to consider these suggestions. He should consider performing diagnostic tests on the system and he might consider the possibility that the fuel sender in the gas tank might not be the proper part.

Carbon deposit causes tapping sound

Q: My 1997 GMC CK1500 has 92,000 miles, automatic transmission, power steering, power brakes, power windows and a 350 c.i.d. V-8 engine.

I change the oil and filter every 3,000 miles.

The other day when I started the truck I heard a tapping sound from the driver’s side of the engine. I shut it off and restarted it but the noise didn’t go away. I live about 15 minutes from work so I drove the truck to work. About half way to work the noise stopped.

I think there may be a lifter going bad. Is there an additive I can pour in the engine to cure the problem. Do you think a faulty lifter is causing the noise? How much will it cost to repair? D.H., Anchorage, Alaska

A: Find the closest glacier, park the vehicle on it, exit and wave goodbye to your truck. Who knows maybe in a million years it will slide all the way to California. Just kidding but from what you describe it would be very unlikely that a lifter is the cause of the tapping. Usually if one lifter fails it doesn’t recover as yours did. What might have happened is a small piece of carbon dropped off a deposit and bounced around in a cylinder for a while. The driving you do is hardly enough for the engine to reach full operating temperature especially this time of year. As a result carbon deposits can form and cause weird conditions such as you describe. Also, since you change the oil and filter every 3,000 miles it’s not likely that sludge and varnish accumulated to impair the proper operation of the valve lifters.

If an accumulation of carbon is the cause of the tapping consider using a top engine cleaning chemical. These are available at many auto supply stores. Follow the directions on the chemical container and the deposits should be gone. After the treatment change the engine oil and filter to remove residue from the cleaning. Also, it might be a good idea to replace the spark plugs as the chemical treatment can leave deposits on the plugs that can impair proper function which can lead to engine misfire.