1992 Chevy Silverado Idle problem

Tiny
SARGENTWOODY
  • MEMBER
  • 1992 CHEVROLET SILVERADO
  • V8
  • 4WD
  • MANUAL
  • 15,500 MILES
Alright.
So, I've had this idling problem lately with my truck.

It idles at about 550-600 rpms. But every few seconds it will drop down to 450-500, sorta like it wants to stall, then go to normal and so on.

Any ideas?

Thanks.
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Friday, March 7th, 2008 AT 7:19 AM

13 Replies

Tiny
BLACKOP555
  • EXPERT
Unhook the IAC module does the problem go away?
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Friday, March 14th, 2008 AT 4:35 PM
Tiny
SARGENTWOODY
  • MEMBER
Yes, that fixed the problem.I started it and it idled like crazy good. What now, I can't just have that unhooked can i? I replaced that part not too long ago. Like 5k miles ago when I had my fuel pump problem. After I replaced my fuel pump and iac and tps is when it started idling weird. So. What now?
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Friday, March 14th, 2008 AT 5:41 PM
Tiny
BLACKOP555
  • EXPERT
Ah now were getting somewhere, sounds like you may have gotten the wrong IAC module and it isnt funtioning properly! If you still have the old one try that.

If that doesnt fix it you may have a bad PCM but I really doubt that.
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Friday, March 14th, 2008 AT 6:06 PM
Tiny
SARGENTWOODY
  • MEMBER
Alrighty.I dont think I have the old one.I may, i'll look, if not, i'll go get a new one and see if that fixes it.

Ill let you know what happens. Thanks!
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Friday, March 14th, 2008 AT 7:20 PM
Tiny
SARGENTWOODY
  • MEMBER
I shouldn't say it idled good. But it definetly idled high. About 1000 rpms. And I dont have the old part, which sucks because it's a 75$ part. I guess ill try replacing it. Hopefully the parts place gave me the wrong part. HOPEFULLY
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Friday, March 14th, 2008 AT 11:42 PM
Tiny
BLACKOP555
  • EXPERT
If that isnt it you may have to take it in and have them try to reprogram the IAC and PCM or replace the PCM.

Is your throttle body clean?
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Saturday, March 15th, 2008 AT 8:10 AM
Tiny
SARGENTWOODY
  • MEMBER
What is the PCM?
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Saturday, March 15th, 2008 AT 10:10 PM
Tiny
BLACKOP555
  • EXPERT
Powertrain Control Module.

It is what controls all the vehicles systems.
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Sunday, March 16th, 2008 AT 7:45 AM
Tiny
TIGERZ
  • MEMBER
I have the EXACT same problem. I have a 1993 k1500

it just all of a sudden started idling like that. The engine also hesitates a little sometimes.
I replaced my air filter(K&N), coil(MSD), new plugs(OEM), and the EGR Valve. I have more power but it still hasnt fixed the problem.
Let me know if you pin pointed what is was. I dont want to keep throwing parts at it.
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Thursday, March 20th, 2008 AT 1:18 PM
Tiny
TIGERZ
  • MEMBER
Idle Air Control Valve was the problem

or IAC

the old one had all this nasty grease and carbon build up. Replaced it and it idled like a champ.

$46.00 at autozone
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Thursday, March 27th, 2008 AT 5:35 PM
Tiny
BLACKOP555
  • EXPERT
Glad the IAC module was the problem not something harder to diagnose :D
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Friday, March 28th, 2008 AT 7:19 AM
Tiny
TIGERZ
  • MEMBER
Looks like my response was a bit premature. Im still having the issue. And I still have an acceleration issue sometimes. The motor just bogs and then kicks in after a second.
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Monday, March 31st, 2008 AT 7:54 PM
Tiny
BLACKOP555
  • EXPERT
Check your TPS sensor resistance at closed throttle and then WOT. Then check it as throttle is slowly opened, should be very steady.

Can you have it checked for a vacuum leak? Take a can of carb cleaner and spray around the EGR valve, the intake manifold, IAC module, throttle body and all vacuum lines.
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Monday, March 31st, 2008 AT 8:32 PM

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