1991 Chevrolet Cheyenne Idle air control valve

Tiny
WIZARD505
  • MEMBER
  • 1991 CHEVROLET CHEYENNE
  • 5.7L
  • V8
  • 4WD
  • MANUAL
  • 165,000 MILES
When I start my truck it idles fine and then all of the sudden the idle air control valve will cut out and start running sluggish like it wants to die out and black smoke starts coming out the muffler then after I rev the engine a couple of times it stops. Then it will run good again then all the sudden it does it again I replaced the idle air control valve with new one and it still does it some days it will be doing fine and then out of nowhere it does it again I replaced all parts on throttle body any idea why the idle air control valve would cut off and cut on. Thank you
Saturday, December 13th, 2014 AT 1:32 PM

2 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
You don't have an IAC problem. Your engine is getting overloaded with fuel for some reason.

You can look at the injectors when the engine is first shut off to see if any fuel is leaking out of them. If not, then it may have a fuel pressure regulator with a torn diaphragm allowing fuel to leak through. Unfortunately on the TBI engine the regulator is not accessible externally so you may have to try a different throttle body to find out. Another way is to use a fuel pressure gauge and see if the system hold rest pressure. If it doesn't, that would be an indicator of a possible leaking regulator.
Was this
answer
helpful?
Yes
No
Saturday, December 13th, 2014 AT 2:43 PM
Tiny
WIZARD505
  • MEMBER
  • 2 POSTS
When my truck starts to run sluggish I unplug the idle air control valve and engine runs the same no change also sounds like it's sucking a lot of air and black smoke starts out of muffler my throttle body also gets so cold that it gets icy around outside of throttle body. Then all the sudden the idle air control valve kicks in and the air sucking is gone, ice melts and engine idles like nothing was ever wrong with it, then couple days later it does it again. Been going on for 3 months
Was this
answer
helpful?
Yes
No
Sunday, December 14th, 2014 AT 2:23 AM

Please login or register to post a reply.

Related Idle Air Control Replace/Remove Content

Idle Air Control Motor Replacement
GUIDE
Idle Air Control Motor Replacement
The idle air control motor or idle speed control motor is designed to adjust the air flow into the intake manifold at engine idle. Engine idle speed is monitored by the PCM...
VIEW MORE