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.

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