Q: Rough idle on acceleration displaying symptoms of a misfire, but there is no misfire codes detected. On cold starts the car is completely normal.

asked by on December 05, 2016

Make: Pontiac Year: 1996 Model: Firebird Drivetrain: 5.7L LT1 V8/4l60 A4 trans Modifications: Pace setter long tube headers/ORY, SLP LM1 exhaust(No cats)

OBDII Codes: P0134 P0134 02 Sensor Circuit No Activity Detected (Bank I Sensor 1) P0141 P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) P0154 P0154 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 1) P0400 P0400 Exhaust Gas Recirculation Flow Malfunction P0443 Evaporative Emission Control System Purge Control Valve Circuit P1441 EVAP System Flow During Non-Purge Condition

Problem: Rough idle/acceleration displaying symptoms of a misfire but no misfire codes located

When is problem notice?: When car is at operating temperature, during full RPM range(I haven't yet tried wide open throttle to test for O2's) On cold starts car is completely normal

What have you already tried?(Will edit as suggestions come): Checked and cleaned EGR, Checked all vacuum lines for any leaks, checked for exhaust leaks(repaired 2), checke

My car has 153456 miles.
My car has an automatic transmission.

Hi there. Since you have a code for the Exhaust Gas Recirculation (EGR), the EGR could act like a vacuum leak and cause a random misfire. Remove the EGR and clean it out and then put it back on. If the symptom gets better but the engine still has a misfire, then I recommend replacing the EGR valve. The EGR valve will cause the O2 sensors to register to the computer and set a code for the O2 sensors. This is normal for the O2 sensors to work. For the EVAP issue, check the gas cap and make sure that the seal is good. Also, check the purge valve on the fuel system and see if its plugged in. Most of the time the valve gets stuck and needs replaced. If you need further assistance with your engine having a misfire, then seek out a professional, such as one from Your Mechanic, to help you.

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