Dr. Gizmo Solves Your Car Troubles - Part II Page 2

November 30, 2009

2009 Chevrolet Avalanche

 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.

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