90 C1500 stalls at idle

Discussion in 'Chevy Truck Forum' started by henslin, Jul 8, 2010.

  1. henslin

    henslin Member

    Joined:
    Jul 8, 2010
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    0
    Truck will stall at idle just sitting there and will be hard to start untill you let it sit a while 60 seconds. Worse when hot. Worse when A/C is on. If you turn the wheel fast it stalls. If you put your foot on the brake and keep the idle up it won't stall. Has 326,000 miles on it. Can't figure why it stalls. Replaced Fuel pump and filter no change. When it's idleing it purrs like a kitten. When floored it runs great. No misses or hesitation. Pulls a 7,000 lb trailer perfectly.
     
  2. 75K30

    75K30 Senior Member

    Joined:
    Jul 19, 2006
    Messages:
    3,690
    Likes Received:
    168
    Trophy Points:
    0
    Welcome to the site:

    Sounds like you have a small vacuum leak.
     
  3. Darkness88

    Darkness88 Member

    Joined:
    Jul 9, 2010
    Messages:
    6
    Likes Received:
    0
    Trophy Points:
    0
    yup or ignition problems. check the timing. does it blow black smoke while idling?
     
  4. henslin

    henslin Member

    Joined:
    Jul 8, 2010
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    0
    Timing perfect. Engine is always strong and idles smooth. Just cuts off while sitting there or the A/C cycling. It's like it won't up the idle under small load.
     
  5. henslin

    henslin Member

    Joined:
    Jul 8, 2010
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    0
    Flooded it with carb cleaner. only stalled when sprayed directly into throttle body. Changed the IAC valve. Ran with high Idle for a little while till it was up to temp. Now does the same thing.
     
  6. 1500cheyenne96

    1500cheyenne96 Senior Member

    Joined:
    Sep 1, 2009
    Messages:
    858
    Likes Received:
    14
    Trophy Points:
    0
    Occupation:
    construction laborer/ hand on family farm
    Location:
    MIchigan
    I would suggest a bad or plugged EGR valve tyr tapping on the EGR lightly with a hammer to see if that helps if not unplug the egr when warm and cold to see it that helps . Also a vacuum leak is a very real possibility did you also spray the booster line with carb cleaner?
     
  7. 75K30

    75K30 Senior Member

    Joined:
    Jul 19, 2006
    Messages:
    3,690
    Likes Received:
    168
    Trophy Points:
    0
    Stuck or leaky EGR, or your vacuum leak is at the brake booster.
    Flooding the engine with carb cleaner is a good start, but vacuum sources are in several places, and the most common and most overlooked area is the brake booster.
    Also make sure that the PCv is functional, and not another small source of a leak.
     
  8. henslin

    henslin Member

    Joined:
    Jul 8, 2010
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    0
    Thanks guys I did spray the brake booster and all the lines. I did change the EGR valve about 100k miles ago when I started getting a check engine light (egr valve) and the light never came back on. It is a cheapo Autozone one though. Now it still idles smooth but I can turn the wheel right or left and it will die under the ps pump load. It's like it just can't give enough rpms fast enough or not at all.
     
  9. zombie1969

    zombie1969 Senior Member

    Joined:
    Jun 30, 2010
    Messages:
    1,016
    Likes Received:
    16
    Trophy Points:
    0
    Location:
    CT
    You sure the iac is working?You replaced it but does it work?It should open and close as needed to maintain the proper idle.You didnt say what its idling at.You have a tac?You have a lot of miles so ajusting the base idle manualy may be needed and reajust the tps if needed.Other than a scan tool Im not sure how to but you can vary the idle up and down through the computer to check it the system is funtional and see if various inputs like the ac kicking on and power assist are being seen.
     
  10. henslin

    henslin Member

    Joined:
    Jul 8, 2010
    Messages:
    7
    Likes Received:
    0
    Trophy Points:
    0
    I don't have a tac but it does seem to idle kinda low. WHen I first put the IAC in it idled high then after I drove it a little it went back down.
     

Share This Page