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

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.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Rough idle on acceleration displaying symptoms of a misfire, but there is no misfire codes detected. On cold starts the car is completely normal.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Timing off from TDC

Hello. It sounds like a new distributor has been installed and is misaligned, causing the timing to be off. The truck timing needs to be set to TDC, then the distributor needs to be reinstalled, and timing rechecked. This should...

Q: Truck hesitates to start

Hi there. All of your symptoms are pointing towards a worn timing chain/belt. A loss of power or "lugging" up a steep grade will be your first sign of a worn timing belt. This is also directly connected to your...

Q: Why does my car loose RPM when I'm driving?

Hi there. First check all of the fluids and make sure that they are full and top off all low fluids. Then check the battery and make sure that it has a full charge of 12.6 volts. If the voltage...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...