Rough idle?

2005 CHEVROLET TRAILBLAZER
160,000 MILES • 4.2L • 6 CYL • 4WD • AUTOMATIC
Avatar
MCLARK22
  • MEMBER
  • 2 POSTS
I am having a rough idle whether cold or hot, the engine bogs down when reversing and occasionally stalls, and there is a lack of accelerating power when A/C is running.
Aug 10, 2023 at 4:13 PM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.
Advertisement
Avatar
STRAILER
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 54,178 POSTS
It sounds like you lost compression in one or more cylinders, do you have a check engine light on? If so, we need to run the codes to see what they are.

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

If you can upload a short video of the engine running, I can tell what is wrong, or at least see what the next step should be. You may have a weak fuel pump as well. Here is a guide to help us test the fuel pressure.

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

Fuel Pressure (Key ON, Engine OFF) .................... 345-395 kpa (50-57 psi)

You can rent a fuel pressure gauge from the auto parts store. Please go over these guides and get back to us.
Aug 11, 2023 at 10:40 AM
Advertisement
Avatar
MCLARK22
  • MEMBER
  • 2 POSTS
I don't have any current codes, but I have had 2 codes in the past. P0303 (misfire cylinder 3). That went away after a full plug and coil change. The plug in cylinder 3 did have oil on the electrode side. (Which I understand is usually indicative of advanced cylinder or piston wear. Just hoping there was something else it could be before I just decide to just drive the vehicle into the ground).
And P0495 (voltage reading that is too high from the electric cooling fan control circuit) which I cleared and it hasn't repeated.
Aug 11, 2023 at 9:12 PM
Avatar
STRAILER
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 54,178 POSTS
If you have low compression on cylinder #3 this will account for the rough idle.

Here is a guide to help you confirm the issue:

https://www.2carpros.com/articles/how-to-test-engine-compression

Please go over this guide and get back to us.
Aug 12, 2023 at 10:08 AM