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Rough idle wont stay running

Tiny
DOM78
  • MEMBER
  • 1994 CHEVROLET SUBURBAN
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 203,000 MILES
Check engine light on but only because the advanced timing wire not plugged in because when it is plugged in it idles rough, runs rich, and dies on me. When unplugged it runs great and there are no codes to be read. I had the whole top of engine rebuilt and timing chain done and gears and harmonic balancer all new and still no hope. Could it be my computer?
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Wednesday, August 10th, 2016 AT 4:17 AM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,389 POSTS
That is a good one, can you check the base timing with the tan wire with the black stripe is unplugged? If okay then I would check all system grounds to make sure they are hooked up. It could be the ignition module or main coil that is shorting out for some reason when the wire is connected.

Here is a wiring diagram to make sure the ground are attached to the engine.

Please let me know what you find

Best, Ken
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Thursday, August 11th, 2016 AT 7:54 PM
Tiny
DOM78
  • MEMBER
  • 2 POSTS
The control module is new and coil new but yeah that's the wire I'm talking about the tan wire with black stripe when it's plugged in it runs like crap but when it's unplugged it runs great but the check engine light goes on because not plugged in. Can it be my ecu/computer?
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Friday, August 12th, 2016 AT 3:32 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,389 POSTS
Yes it can be, here is one you can buy from amazon

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=1994+CHEVROLET+SUBURBAN+ecm&rh=i%3Aaps%2Ck%3A1994+CHEVROLET+SUBURBAN+ecm

Please let me know how it goes

Best, Ken
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Friday, August 12th, 2016 AT 11:05 AM

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