1998 GMC Sierra what is going on here HELP!

Tiny
ROSHIER8
  • MEMBER
  • 1998 GMC SIERRA
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
Hi, My truck starts fine. Sometimes has extended turn over. The problem is that as soon as I put it in gear it starts idling funny. If I give it gas it spits and sputters. If I don't touch the gas and let it drive at idle it clears up in about 10-15 seconds then runs fine. It only acts up again if I try to accelerate too hard (put it to the floor) then it almost backfires. Any info would be greatly appreciated.
Thanks, Rick
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Monday, September 27th, 2010 AT 9:02 AM

5 Replies

Tiny
HMAC300
  • EXPERT
Check your electrical connections on the mainifold. Then replace your fuel filter if you havn't so far and get some choke cleaner and clean both sides of the throttle plate as they tend to gum up with oil deposits. If that doesn't cure it have a pro check for cracked fuel lines under the manifold.
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Saturday, October 2nd, 2010 AT 8:49 PM
Tiny
ROSHIER8
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Have done these things. What about the throttle position sensor would that be possible
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Monday, October 4th, 2010 AT 11:05 AM
Tiny
HMAC300
  • EXPERT
If there is a lot of gunk and crap around the tps it could cause it, but you can clean that with choke cleaner and most of the tps switches are covered anyhow. YYou can try it won't hurt. Usually it will set a engine code though. You might check the resistance on the crank and cam sensors and see if it is high. They can go bad and not set a code. The olny other thing I can think of would be low fuel pressure. Yours should be anywhere form 60-66 p.S.I. But I kind of doubt that due to you saying it runs fine after the initial startup.
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Monday, October 4th, 2010 AT 5:37 PM
Tiny
ROSHIER8
  • MEMBER
Now reading an o2 sensor code would that cause symptoms or just a coincidence by the way thank you for the reply
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Tuesday, October 5th, 2010 AT 4:50 AM
Tiny
HMAC300
  • EXPERT
The O2 sensor could cause the problem of poor idling but it would effect everything while driving. And it depends which O2 sensor it is. There are 4 pre and post- 2 before the converter and 2 after. The post ones don't effect things to much. But if it says like bank 1 sensor 1 that is the one on the left siide before the converter. You could try tit but they are exspensive but they will need replacing anyhow. This could be a coincidence as well. If that doesn't clear it up i'd have apro in your area look at it as intermittent problems like that are hard to find as well as diagnose, especially on here.
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Tuesday, October 5th, 2010 AT 9:34 AM

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