Erratic Idle/engine shuts off in reverse

Tiny
CASHFLOW50$
  • MEMBER
  • 2003 GMC YUKON
  • 4.8L
  • V8
  • 2WD
  • AUTOMATIC
  • 130,000 MILES
My car is the SLE model.
Pulled in garage after dropping my daughter off at her volleyball practice. Took a two hour nap while waiting. After my beauty rest jumped in my ride and started her up. Started like a champ. Started pulling out on reverse and all of a sudden engine just shut off. Started her back up with no problem. What I noticed was the change in idle. On reverse needle on gauge went below 500 rpm. Maybe at 400 or so. It slowly went back to 700 moments later. I then placed her in drive and same thing drop below 400 or so then gradually rises up. What the heck is going on? Dirty MAF sensor? Dirty throttle body? Plugs going bad? Please help. Thank you.
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Thursday, June 22nd, 2017 AT 12:52 PM

8 Replies

Tiny
KEN
  • ADMIN
Hello,

Yes all of the above can cause the problem along with a weak fuel pump, here are some guide that will get us started in the right direction.

https://www.2carpros.com/articles/mass-air-flow-service

and

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

and

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

and

https://www.2carpros.com/articles/how-to-change-spark-plugs

and

https://www.2carpros.com/articles/stall-at-idle

Please let us know what happens, we are interested to see what it is.

Cheers, Ken
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Monday, June 26th, 2017 AT 10:26 AM
Tiny
CASHFLOW50$
  • MEMBER
Thanks for the reply Ken. It was actually the maf. I removed it and the intake tube as well. Cleaned both maf and throttle body with their respected cleaners. After clean idle is back to normal and never drops below 700. I was relieved, because I was thinking it was the TCC solenoid. I was hoping not to drop the trans pan to get to it.
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Wednesday, June 28th, 2017 AT 10:21 AM
Tiny
KEN
  • ADMIN
Nice work, we are here to help, please use 2CarPros anytime.

Cheers, Ken
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Wednesday, June 28th, 2017 AT 11:37 AM
Tiny
CASHFLOW50$
  • MEMBER
Hi Ken.

Kind of jumped the gun a little. It was driving fine for a bit, but the dreadful CEL on the dash along with a message stating 'Reduced Engine Power' on dic. I pulled the codes and got P1518 which points to the Throttle Body. Maybe I sprayed too much Carb cleaner in the area and got the wires wet somehow. Going to check the connectors before I buy a new TB.
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Wednesday, July 5th, 2017 AT 10:49 AM
Tiny
KEN
  • ADMIN
Please let us know what happens, we are interested to see what it is.

Cheers, Ken
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Wednesday, July 5th, 2017 AT 6:05 PM
Tiny
CASHFLOW50$
  • MEMBER
All connectors pertaining to the TB all good. I shook them and still didnt post any error code(s). Did more research on the P1518 and it could be a bad tac module, which I just ordered. I'll update once I have replaced the part.
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Thursday, July 13th, 2017 AT 1:03 PM
Tiny
KEN
  • ADMIN
Please let us know what you find.

Cheers, Ken
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Thursday, July 13th, 2017 AT 5:15 PM
Tiny
CASHFLOW50$
  • MEMBER
I installed the tac module yesterday. Took her to work this morning and so far so good. It was fairly easy to remove and install. Hopefully code wont come back. Crossing fingers.
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Tuesday, July 18th, 2017 AT 9:54 AM

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