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?
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: Idle Problem/Engine Misfire Code P0300 P0301 P0303

Hi there. Check the spark plugs and fuel injectors for cylinder 1 and cylinder 3. Both cylinders are misfiring. If the plugs are good and the fuel injectors are firing, then there could be a problem with the internals of...

Q: Coolant doesn't circulate and is leaking into coolant tank

Hello. If the coolant only leaks when the engine is running, then it is typically a failing water pump. This is the most common thing to leak under these conditions. The water pump should be checked for signs of leakage...

Q: Is it safe to drive with a misfiring cylinder?

Hey there, thanks for writing in about your Jeep Wrangler. I would recommend getting it checked before going away on your trip. The misfire code may be a problem with the variable valve system or the ignition system. With this...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
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...
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...