Dr. Gizmo Solves Your Car Troubles - Part II

November 30, 2009

Clicking Tappets Not Normal 
Question 1
I have a 1991 Audi 90 Cabrio with a 2.3-liter engine and 150,000 miles.  For the last six months when I start the car, the tappets do not click.  Up until six months ago, they tapped up to 10 minutes after a cold start.  Now they only tap for three seconds after a cold start.  Also, the engine lacked power.  I am very worried and upset.I have thrown a lot of money into this car.  In the past six months, I have been to three mechanics to have the lack of power, rough idle, poor fuel economy, low compression power in cylinder 5 and tappet issues repaired.  They have replaced the starter motor, five fuel injectors, air control valve, throttle position valve, cylinder head gasket, manifold gaskets, distributor, ignition wires, oil pressure valve, water temperature sensor, fuel pump, fuel filter and fuel pressure regulator.  These are all brand name parts.
The car runs fine now, but the tappets are not clicking. I am at a loss.  Right now, I am taking a bus to and from work because I cannot trust my car.  Can you help? B.F., email.

Answer 1
At first, I thought you were playing a joke on Dr. Gizmo, but you are as serious as a natural disaster.  You have spent thousands of dollars and taking the bus.  This is an unnecessary nightmare.  Please, sit down, take a breath and relax.
Your car is running fine and it is not ticking.  It is not normal for the engine to click for 10 minutes after a cold start.  The reason it ticked before repairs were performed is the tappets were not receiving proper oil pressure.  Your engine has hydraulic lifters that fill with pressurized oil when the engine is running.  When oil pressure is low, the lifters lack pressure and the rocker arms that open and close the valves click.  Once a mechanic replaced the oil pump, the oil pressure returned to normal and the hydraulic lifters quit rattling.  Now when you start the engine oil pressure quickly builds and the clicking stops a few seconds after you start the engine.  This is normal.  Your 90 is waiting for you to take it for a drive.  Hit the road with confidence.

Low Voltage Causes Issues In Instrument Panel
Question 2
The instrument panel in my 2001 Chevrolet Corvette is going nuts.  Also, the hour meter, trip meter and average gas mileage suddenly quit without any warning reset.  Other than this problem the car looks, starts and runs like new. What would cause this problem?  Does the instrument panel need repair or replacement?  G.G., email.

 Answer 2
I don't know where you reside, but if you live in the Snow Belt, it is time to tuck your baby away for the winter.  Also, it might be time to replace the battery. The problem you describe is consistent with a low voltage condition.  This might be caused by poor battery cable connections at the battery terminals due to corrosion or a loose connection.  It is possible the battery no longer holds a full charge and needs replacement.  It is also possible the alternator belt is worn or not in proper tension to turn the alternator sufficiently to charge the battery.  Maybe the alternator has a fault that results in an undercharged battery.
Do not replace the instrument panel until the battery and charging system and been inspected and tested.  If there is a low voltage condition, a successful repair will likely end all erroneous instrument activity.

 Engine Modification Leads To Trouble 

Question 3
Recently, I modified the engine in my 1996 Nissan 300ZX.  I changed it from a normally aspirated engine to a twin-turbocharged engine.  After installing the turbo chargers, the fuel injector O rings leaked.  After repairing this, the timing belt shredded because a bolt broke off an idler pulley.  Then the valves in two cylinders bent.  Then the engine did not perform to its full potential so I installed an engine control module for twin-turbo engines.  Now the engine runs better, but idles rough.  I scanned the computer to find that the right bank cylinders are running lean.
What would cause this condition?  M.Z., email.

 Answer 3
Wow! What a story.  I recall receiving a letter from another reader a few years ago who had a similar experience after such a conversion. Test the oxygen sensors.  If they failed, replace them.  Check the exhaust manifold for air leaks.  Repair as needed.  Test the fuel pressure regulator and replace if it fails tests.  Test the mass airflow sensor.  If it fails tests, replace it.  Also, test for air leaks at the intake manifold and repair as needed.  Since the turbos are pumping pressurized air into the intake, it is likely the original gaskets on the manifold failed.  If they have, installation of new gaskets is the cure.

Contaminated Engine Coolant Causes Poor Starts

Question 4
When the engine is cold in my 1985 Chevrolet Z28 Camaro, it starts without any problem and runs great.  However, if I stop a few miles later and restart the engine it cranks up to 15 seconds before it starts.  When it starts black smoke pumps from the exhaust.  Also, sometimes while driving the check engine light turns on. I have tuned the engine and the timing is perfect.  Also, I checked for trouble codes.  Code 32 popped up indicating the exhaust gas recirculation valve has a problem.  I have not replaced it because the light turns off and stays off for weeks at a time.
What should I do to fix the hard starting problem?  Should I replace the EGR valve?  C.I.D., email.

Answer 4
Engine coolant temperature and air temperature signals to the engine control unit must be correct for the engine to start without fault.  It is possible the coolant temperature sensor is operating near designed limits and needs replacement.  Testing should determine if it has a fault.  In addition, it is possible the mass airflow sensor is dirty or needs replacement. Test the coolant sensor.  Replace it if necessary.  Also, if the engine coolant is acidic, flush the cooling system and fill it with a fresh supply. Next, clean the mass airflow sensor and the throttle body unit.  Cleaning these parts might cure the condition.  If not tests may find that the airflow sensor needs replacement.

Clogged Port Causes Misfire

Question 5

My 2000 Ford Windstar with 139,000 miles idles rough, misfires and the check engine light turns on while driving.  The van has a 3.8-liter V-6 engine.  I took the car to an auto store where a person checked the engine computer.  His tester found a misfire in cylinder five. I replaced the spark plugs, ignition wires, air filter, fuel filter and ignition coil.  This did not cure the misfire. I returned to the auto supply store to have the computer checked again.  The tester found that cylinder five is still misfiring.  Do you think the fuel injector is the cause of the misfire?  D.K., E-mail.

 Answer 5

You have performed a lot of work.  Your reward will be a lasting repair.  It is possible that fuel and combustion deposits impair the fuel injector.  Add fuel injector cleaner to the fuel tank.  This may dissolve deposits and cure the trouble.  If not, there may be a poor electrical connection at the fuel injector or the fuel injector needs replacement.

 In addition, it is possible there is a problem in the exhaust gas recirculation system.  Perhaps the valve has a fault and needs replacement.  It is also possible carbon deposits are plugging a port to the EGR valve.  Unplug the vacuum line to the valve and cap it.  If the misfire stops, it is likely that deposits have plugged the port to the valve.  If so, the intake plenum needs disassembly to clean the deposits from the port.

 New Or Rebuilt, Compare Warranty 

Question 6
The pump for the antilock brakes in my Chevrolet Avalanche runs continuously.  I took the truck to my trustworthy local independent shop where a technician says the ABS module needs replacement.  This is expensive. Is there anything I can do to reduce the cost of this repair? H., email.

Answer 6
To reduce costs some repair shops send antilock brake system modules to a company to have the module rebuilt with great success.  In addition, some repair shops have had bad luck with rebuilt modules so they prefer to install new factory original equipment parts.  Ask your shop technician if uses remanufactured parts or new OEM parts.  If he is willing to use a reconditioned part, you will save a few bucks. Be sure to compare the warranty between a new original equipment part and the remanufactured unit before you decide on which part to install.
Thanks for all of your great questions.  Dr. Gizmo cant wait to answer more.

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Phil Arendt is a columnist, consultant and A.S.E.-Certified Master Technician.  Readers may send questions to Dr. Gizmo at P.O. Box 548, Cary, IL. 60013 or e-mail address [email protected]

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