Will not accelerate over 40 MPH

Tiny
BIGED2021
  • MEMBER
  • 2002 PONTIAC GRAND AM
  • 3.4L
  • V6
  • 2WD
  • AUTOMATIC
  • 139,000 MILES
My car won't go over 40 MPH, it acts like something is pulling it back. I can push the pedal to the floor, and it won't go past 40 MPH. This is my only vehicle and I've got to get it fixed.

Why is it doing this?

Also, it has no catalytic converter.

Sunday, March 6th, 2022 AT 5:45 PM

3 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
We need to start with checking to make sure the throttle cable is correctly installed in the bracket of the throttle body so that when you press the accelerator it is getting the full travel.

You can do this by having someone push the throttle and you watch the throttle plate and make sure it is fully opening. The engine can be off to do this.

I attached a picture below of where this attaches.

Next thing is to check for codes. Here is a guide that will help with this:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If there are no codes, then we most likely have a fuel or air intake sensor issue. Also, we could have a restriction but if there are no converters then this is less likely so I would focus on this guide to help with these causes:

https://www.2carpros.com/articles/symptoms-of-low-engine-power

https://youtu.be/U1RoG3I-Oww

Please run through all this info and let us know what you find. However, based on all this, I suspect we are going to have a MAP sensor issue or some other intake air issue.

Please let us know what questions you have.

Thanks
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Monday, March 7th, 2022 AT 4:07 PM
Tiny
BIGED2021
  • MEMBER
  • 21 POSTS
The cable is working properly.
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Tuesday, March 8th, 2022 AT 12:25 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. So, if it is not a mechanical issue then we have a sensor issue and more than likely this is a MAP sensor issue.

Were you able to check for codes? I imagine you have o2 sensor codes but if we have others then that will cut down on a lot of this diagnostic work.

Otherwise, we need to monitor the MAP with a scan tool while driving and see what the reading is to determine if this is seeing the correct amount of air coming in.
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Tuesday, March 8th, 2022 AT 5:06 PM

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