Engine stutters at idle when the A/C is on

Tiny
RANDYRHODES
  • MEMBER
  • 2005 CHEVROLET TRAILBLAZER
  • 4.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 135,000 MILES
I've replaced the MAP valve and Air filer, plugs, oil change. I also thoroughly cleaned the throttle body.
Friday, June 3rd, 2022 AT 7:54 AM

3 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
If this only happens when the A/C is on the we may have an issue with the compressor or compressor clutch.

Basically, when these start to lock up they can cause engine misfires or even snap drive belts.

So, I doubt this is a sensor issue that is causing the engine to run poorly but it could also be a fuel supply issue.

So, let's start checking these two things.

First let's start with the A/C pressures when the compressor is on and off.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

If the pressure is low, then that will show a compressor issue as well.

So, if this checks out then we need to check the fuel pressure with the A/C on and off.

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

Let's start with this and then we can go from there.

Thanks
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Friday, June 3rd, 2022 AT 7:12 PM
Tiny
RANDYRHODES
  • MEMBER
  • 2 POSTS
I've since changed the up and downstream oxygen sensors, the air temperature control unit in the engine, the emission system including the charcoal canister and other components. I recently ordered a professional air conditioner recharge kit, including vacuum pump and today am going to test the amount of Freon and check for leaks. I will also vacuum and recharge if it is off and not leaking. Once this is done, if the car still stutters, I can only assume it must be something else. It has been fun collecting new tools and learning/changing parts, but I'm ready to fix this for good. Should I just buy a new compressor or what? In fact, there are no new sensors left. They are all new.
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Monday, June 13th, 2022 AT 6:27 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
I think the important thing at this point is to gather data and not just change the parts like the compressor. That makes us assume that the system or part is not the issue.

Let's see what happens with the A/C and vacuum the system and then go from there.

Thanks
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Monday, June 13th, 2022 AT 6:49 AM

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