Low idle and stalling on 2003 Suburban 5.3 - IAC??

Discussion in 'GM Powertrain' started by ElbowJoe, Jan 27, 2011.

  1. ElbowJoe

    ElbowJoe Member

    Does anyone know if a 2003 Suburban 1500 with a 5.3L Flex fuel engine has an IAC valve? I am trying to troubleshoot an idle issue and was hoping it was something easy like cleaning the IAC valve.

    Here is the issue: My normal op temp idle drops below 500 RPM and once and a while stalls when stopping or going from reverse to drive when backing out of the driveway for example. I tried a reset of the PCM by disconnecting the battery and re-programming as directed in the Chilton manual - but this did not seem to adjust the idle to the targeted 650 RPM.

    My next course of action will be to get out the carb cleaner and spray down the mass airflow sensor and see if that helps. I have approx 120k miles. Plugs and PCV are new at 100K and air filter (K&N) is clean. One other observation that may or may not be associated with this issue. I have also noticed some knocking under full throttle acceleration and once and a while the check engine light illuminates during a full throttle jaunt when getting on the expressway. I have not had a chance to check the code with a scanner and the light normally goes off when the engine has been turned off for an hour or so. I have been told that this may indicate a clogged converter. I am hoping it is something less costly which is why I was looking for the IAC or associated components.

    Any ideas?? I am baffled...:confused:

    Thanks in advance!
  2. murdog94

    murdog94 Epic Member 5+ Years 5000 Posts

    DONT spray the MAF with carb cleaner, only use Maf Cleaner or you will destroy it. Also try pulling the Throttle body and clean that with throttle body cleaner (carb cleaner will eat the coating on the metal)
    as to an IAC no i dont believe so you have a Computer controled drive by wire engine. But alot of people have had trouble with plugged up throttle bodies and cleaning them has helped.
    Also be sure to pull that code since that will tell you alot. and with out pulling the actual code it is basically impossible to id why the CEL is on.
    Oh and just so you know im not yelling above just trying to warn you before you have problems.
  3. ElbowJoe

    ElbowJoe Member

    Thanks Murdog94! I will make a trip to O'Reilly's (Murray's) and get the appropriate solvent, then give it a go this weekend and report back. I appreciate your near light speed response and tips!!

  4. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    CRC makes the only MAF cleaner I've ever seen, it's in a silver can. I would also get some throttlebody cleaner. I like to take the throttlebody off so I can clean both sides good with a old SOFT toothbrush and the throttlebody cleaner. Also sweet '68.
  5. ElbowJoe

    ElbowJoe Member

    Thanks Silveradotrailblazer! I am headed down to pick up some cleaning supplies right now. Armed with the tips from you and murdog94, I will check things out and give it a shot.

    Much appreciated!
  6. ElbowJoe

    ElbowJoe Member

    Quick update.

    I pulled the MAF and throttle body off last night and gave them both a thorough cleaning. The MAF did not look bad at all - but I gave it a good spray anyway from both sides. The throttle body was a bit carboned up and I did use a toothbrush to clean both sides, the butterfly and sealing surfaces. The CRC TB cleaner does not clean that well. Not like I expected that is. The power of the spray alone was not enough to remove the carbon residue - even after scrubbing with the brush, so I resorted to using a lint free cloth and soaked it with the solvent. This worked pretty well. I also used the same method and reached in the intake as far as I could. It was late when I finished so I could not take it out for an immediate test drive.

    I did so after work today and it was amazing how much better the Suburban ran. Like it was new. No indication it was even thinking about stalling and the RPM was back up to the expected level when backing up my inclined driveway. Acceleration was smooth with no indication of spark knock on a full throttle jaunt on the on ramp. I will take it out for a longer drive this weekend and see how it does on trip - but for now things look very good.

    Thanks to you both murdog94 and silveradotrailblazer!! I'm going to throw in a bottle of FI cleaner in my next fill up - just because.
  7. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Doesn't hurt to clean the MAF and throttlebody once or twice a year.
  8. sk8willy1

    sk8willy1 New Member

    Thank You Guys so much for this post Thread!!!! I was having the exact same issues with my 2003 K1500 Suburban, and you really saved me a ton of time and headache!!! I only pulled off the throttle body so far and cleaned it up and took it for a drive, seemed to resolve the issues that I was having (Same as ElbowJoe). On a Side note, I was also having "Jumpy acceleration" when moving from a stop. That seems to have also been resolved by the Throttle Body Clean. I will Clean the MAF Tomorrow when it gets light out again.

Share This Page

Newest Gallery Photos