Running rich, rough idle and stalls when driving?

Tiny
NQBQDY
  • MEMBER
  • 2000 JEEP GRAND CHEROKEE
  • 4.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 187,000 MILES
Hello, I have the vehicle listed above Laredo. I purchased it a little over a week ago knowing there was a problem with the fuel system. I started by checking the spark plugs because the previous owner told me he just changed them. They were auto light and carbon found, and he had only replaced five the other three were Bosch and I think one may have been original. The vehicle has 187,000 miles on it but is in really good shape cosmetic wise and I believe it had been pulled behind a motorhome. I replaced all of the spark plugs with Bosch platinum and I have also replaced the throttle position sensor in the coil on plug packs. It has a rough idle, it is running rich, and I can smell gas while it's running. I believe there is an exhaust leak somewhere behind the engine as well. I also replaced a bad thermostat. It also has a knock or tapping sound, but I believe that to be the camshaft as it comes from the center of the engine. When I try to drive it, it will stall several times but when in park and above 1,500 RPMs it seems to smooth out and run well. Thank you for any advice.
Friday, August 19th, 2022 AT 10:14 AM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,536 POSTS
It sounds like you have a bad fuel injector which is leaking raw fuel into the engine, I would remove the fuel injectors and test them which is easy to do.

Here is a guide to help you get started:

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Here is how you can remove the injectors on your car in the images below.
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Friday, August 19th, 2022 AT 10:57 AM
Tiny
NQBQDY
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Okay, thank you I was wondering. This morning I was checking the resistance across the injectors, but I know that doesn't tell you if one is clogged and stuck open. I will get on this and keep you updated thanks again.
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Friday, August 19th, 2022 AT 11:00 AM
Tiny
KEN L
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  • 47,536 POSTS
Sounds good, I hope this is the issue it sure sounds like the injector is the problem.
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Saturday, August 20th, 2022 AT 4:09 PM
Tiny
NQBQDY
  • MEMBER
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Good morning, Ken, hope all is well. Sorry I took so long to get back to you. I recently had surgery and I'm still recovering. I just wanted to let you know that I ended up just replacing all of the fuel injectors, but that didn't seem to change the symptoms. I also ordered and installed a new map sensor. I reset the PCM as well for the new injectors. So just to recap I have replaced the plugs, coils, injectors, TPS, and the MAP sensor. If there was any change in it all I would say it runs slightly worse by which I mean it seems to idle it slightly lower RPMs now and sometimes will shut off just idling in park in the driveway which is a new symptom. One other thing I noticed is that I don't think I brought it up before, it doesn't seem to change RPM whether it's in gear or if I put it back in park or neutral. Thanks again for any advice, happy Labor Day.
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Monday, September 5th, 2022 AT 5:09 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,536 POSTS
Okay, first I would change out the spark plugs to the OEM recommendation which is:

Spark Plug Type .................... RC12MCC4

Next, let run the codes to see what comes up.

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

Next you said it had an exhaust leak. If this is before the primary oxygen sensors it can cause a false reading, this will make it run rich. Also, when you change the plugs out see if one looks different than the rest. Let me know.
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Monday, September 5th, 2022 AT 10:44 AM

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