Skip the auto shop - Our mechanics make house calls

Q: I have an intermittent misfire - 2002 Pontiac Grand Prix

asked by on

My car is misfiring intermittently. It started out as nothing i noticed and the car would throw code P0300 which is random misfire. I replaced upper and lower intake gaskets, replaced map and MAF sensors, and cleaned the throttle body. Now I'm getting code P0403 which is the EGR. It misfires heavily when shifting when the throttle is wide open. Could a sticking EGR cause this? Misfire only occurs when at wide open throttle during shift from 1st to 2nd.

My car has 142555 miles.
My car has an automatic transmission.

Hi and thanks for contacting YourMechanic. The EGR can cause a misfire if it is stuck open when the engine is cold or running at a lower speed. The EGR replaces some of the air with burnt fuel to help cool the engine down, but when trying to accelerate, the engine will starve for fuel and cause a misfire.

Remove the EGR, clean it out and put it back on and retest the engine. I recommend replacing the EGR. If you need further assistance diagnosing the misfiring issue, then seek out a professional, such as one from YourMechanic, to help with your vehicle.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
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. I have an intermittent misfire - 2002 Pontiac Grand Prix

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: P0201 p0300 p0301 p0302 check engine light flashing. Good place to start?

Hello and thanks for your question. There is a misfire detected between cylinder 1 and cylinder 2. The codes P0301 and P0302 are directly related to cylinder 1 and cylinder 2. The code P0300 means that there is a random...

Q: I want to know what engines would fit my motor mounts properly

Hello. The biggest engine that this vehicle originally came equipped with was the 5.7L V-8. This is the 350 cubic inch version. I am not sure what modifications to your vehicle that would need to be done to make this...

Q: Engine shake when started and oil pressure gauge dropped to zero.

Hi there - nice ride! I would first get the oil level back up to "Full". hopefully this was less than a quart low. I would also get a real gauge on the oil pressure to know precisely what oil...

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...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.