Car stumbles while driving

GRANPRIXVIXEN

MEMBER
2005 PONTIAC GRAND PRIX
6 CYL
TURBO
2WD
AUTOMATIC
285,000 MILES

When you push the gas pedal the car stumbles. It's like it shuts off and starts back up. Changed Crank sensor, ICM, MAF, New plugs and wires all new coils, but it still does it. It's been doing it for a few months but has gotten worse. No check engine light is on. So do you have any clue as to what might be wrong with it?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

Have you checked fuel pressure? If you haven't a weak pump it can certainly cause this. Also, an engine vacuum leak can cause it.

Do me a favor, first check if there are any vacuum leaks. It's not hard to do. Follow the directions in this link and let me know what you find:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If there are no leaks found, then I would confirm the fuel pressure is within spec. You may have a weak fuel pump. Here is a link that explains in general how this is done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

One other thought is a partially plugged catalytic converter, but let's cross that bridge if the two suggestions aren't helpful.

Take care,

Joe

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Tuesday, April 19th, 2022 AT 4:10 PM

GRANPRIXVIXEN

MEMBER
3 POSTS

Thank you very much for the reply. Took it to a garage, he tested the fuel pressure. When it did stall it was good according to the mechanic. No air leaks that I can find. No codes thrown whatsoever. No engine light is on, I know the engine light does work because the coil went out and the light came on and went off when I replaced the coils. Do you have any other ideas of what I can check? When you drive it easy it runs fine? It seems like when you accelerate passing gear that's when it cuts out. I have also replaced the air filter. Thank you

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Tuesday, April 19th, 2022 AT 4:34 PM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

It could be related to a partially plugged catalytic converter.

Take a look through this link and let me know if you feel anything mirrors what you experience:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

I will watch for your reply.

Take care,

Joe

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Tuesday, April 19th, 2022 AT 6:01 PM

GRANPRIXVIXEN