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Ask Chris (aka- Moose) Your Own Question
Chris (aka- Moose)
Chris (aka- Moose), Pontiac Technician
Category: Pontiac
Satisfied Customers: 45534
Experience:  16 years of experience
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I HAVE AN '04 BONNEVILLE GXP WITH THE 4.6L ENGINE. ENGINE

Customer Question

I HAVE AN '04 BONNEVILLE GXP WITH THE 4.6L ENGINE. ENGINE IDLES FINE, ENGINE GOES IN TO LIMP MODE WHEN TRYING TO DRIVE IT. CODES ARE: p0300 RANDOME MISFIRE, P0101 MASS OR VOLUME AIR FLOW CIRCUIT RANGE, P 0353 COIL C PRIMARY/SECONDARY CIRCUIT, P0455 EVAP EMISSION SYSTEM LEAK DETECTED(GROSS LEAK/NO FLOW). WHAT I HAVE DONE IS; CHANGED REAR BANK OF COILS, ALL THE SPARK PLUGS, MASS AIRFLOW UNIT, AND SPRAYED ALL AROUND THE INTAKE WITH CARB CLEANER LOOKING FOR VACCUUM LEAKS, NONE NOTED.
Submitted: 1 year ago.
Category: Pontiac
Expert:  Chris (aka- Moose) replied 1 year ago.

Did these repairs address any of the codes you have?

None of these codes should result in limp mode, were there other codes?

Customer: replied 1 year ago.
There are no other codes and yes changing the MAF sensor, plugs and coils, checking for intake leaks was an attempt to correct the codes/ problems.
Expert:  Chris (aka- Moose) replied 1 year ago.

After you did your repairs, and cleared the codes. Then drove it 5 times, what codes returned?

Customer: replied 1 year ago.
the codes have come back each time I did work and cleared them. the car can barley get to 20 mph, and that is with the engine rpm above 3500. there are, nor has there been any transmission codes, the check eng light flashes too.
Expert:  Chris (aka- Moose) replied 1 year ago.

If I disregard the codes and respond based on the information and symptoms. The flashing check engine light is for a misfire. The max speed of 20mph makes this look like a transmission issue, or a restricted catalytic converter. Do you own a vacuum gauge to check the vacuum at idle operating temp? Have you checked the fuel pressure? If you remove the line from the EVAP and block the line, does that help with the EVAP ruled out? Can you run a compression test to verify all cylinders are contributing equal? Can you test the injectors and coils to verify they are getting power and command from the computer to pulse?

Customer: replied 1 year ago.
my scanner is basic, I can see what the manifold pressure is reading, I can not check coils or injectors. If the cat, or Cat's are plugged should that throw an O2 code? I can remove an upstream o2 sensor to open up the exhaust and test for a restriction. and which vacuum hose do you think I should plug, this engine has many.
Expert:  Chris (aka- Moose) replied 1 year ago.

Converter issues associated with restriction does not result in O2 codes.

Yes removing the upstream O2 sensors for a short test drive is okay to do to rule out the converters.

You would remove the vacuum line from the EVAP vent valve that dumps fuel tank vapors into the intake.

Customer: replied 1 year ago.
i disconnected the Cat and it ran much better, then I reconnected the cat and put some Cat cleaner in the fuel tank and drove it for about 45 minutes, running better, not like it should, but better. cleared codes and none returned. every now and again the oil pressure gauge goes to zero then right back up to normal.
Expert:  Chris (aka- Moose) replied 1 year ago.

On the oil gauge you would need to hook up a pressure gauge to test the oil pressure to see if the gauge or sending unit is to blame.