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07 Silverado 5.3 with oil in the air intake boot ... ???

Discussion in 'GM Powertrain' started by Bowtie Junkman, Oct 24, 2011.

  1. My son's truck is a 2007 Silverado (new body) 1500 2WD with the 5.3 with approximately 50K miles on it. We bought it used about 6 months ago ...

    I was driving it a couple of months ago, and the check engine light came on (out of the blue). It ran and drove just fine, so I waited until after work and brought it to my buddy's shop to check the codes. It came back with a sensor problem in the idle circuit (sorry, I do not remember the exact code). Since it had no real "symptoms", we cleared the code and went on with our lives as if nothing ever happened ... never had any symptoms and the light never came back on. My buddy suggested I take a look at the throttle-body to see if it was gummed-up, but since the problem seemed to clear itself up, I didn't give it another thought.

    Then, over this weekend (some 2 months since the first issue), it started acting funny. At start-up, it would start and die. Even pressing on the gas yielded no response from the engine at times, and it took several times (5-8) starting it for it to finally idle properly on its own. Then, while driving and stopped at a light, I noticed the idle was kind of high (like around 900 RPM).

    When I got it home, I took apart the intake ducting. There was in fact oily residue on the throttle blade and lip of the throttle-body. I manually held the throttle blade open while cleaning it out with a clean rag as much as possible. But even more peculiar, there was oil in the rubber connector hose between the throttle-body and the plastic air intake "diaphragm" or "box". And not just a residue ... there was a shiny "puddle" of oil in each of the ridges of the air intake boot. I followed the system back to the air-flow sensor and the air-cleaner box, but there was no oil or residue present there .... just in the boot directly connected to the throttle-body. After cleaning everything and putting it back together, I started it immediately and it seemed OK. But later that day, had the same problem not wanting to stay idling at start-up and dying. It has been driven a few times since, and been fine. Oh yeah ..... NEVER a check-engine light back on again ...

    Two questions ...
    1) Since I manually messed with the throttle blade while it wasn't running, should I disconnect the battery so it can re-learn?
    2) Where the hell is the oil coming from? I know there is the small tube that leads from the air diaphragm/box to a metal tube that runs along the top of the passenger side valve cover ... is that connected to the PCV system? It would make sense if it was, because that would mean the air intake was sucking oil from the motor ... but I thought the PCV valve was at the back of the LEFT (driver's side) valve cover. And I also read the newer trucks were equipped with the new style PCV valve that did not need replacement?


    Thanks in advance for any insight ...
  2. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts Platinum Contributor

    I will be first to say that I have never worked on anything newer than an 05', BUT one thing you never want to do is manually open the butterfly in the throttle body on a drive by wire setup. On the older one's the TPS and IAC were all able to be gone through a manual relearn process, but on the new one's they actually have to be sent through a relearn through the pcm with a TECH2 or better. I just hope you didn't do any damage to the throttle body, the damage is already done.

    I haven't the slightest clue about the oil though.
  3. Update ...
    Disconnected battery for 45 mins two nights ago to "reset" the system ....
    So far, no problem dieing on start-up since ...
  4. GM Customer Service

    GM Customer Service Rockstar 4 Years 500 Posts

    I am glad to hear that your concern seems to have been resolved. Please feel free to contact me in the future with any questions or concerns that may arise. Thank you.

    Tricia, GM Customer Service.
  5. I spoke too soon .... my son is at school and it won't stay running ....
    only before, after a few tries, it would eventually start and then idle on its own as normal ...
    now, it WILL NOT stay running after NUMEROUS tries .... and a mysterious 'clicking' noise from under the hood ... and as before, no response from the engine when depressing the pedal while trying to keep it running ....
  6. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts Platinum Contributor

    You really need to get a hold of somebody who can scan that truck, and see what the tps voltage is. I would be willing to bet it needs a relearn, because it has lost position and it will not just clear up with disconnecting the battery. Honestly for what the relearn would cost for that truck, you could buy a used throttle body off of craigslist or somewhere for a lot cheaper. Or a junkyard for that matter, hopefully someone else can shed some light on this.
  7. My "handle" refers to the fact that I have been in the auto wrecking business my whole life .... owning my own yard for 10 years ... and having a soft spot in my heart for Chevys (wiping tear from the corner of my eye) ....
    Even with a used throttle-body, wouldn't it still have to "re-learn" ?
  8. TRPLXL2

    TRPLXL2 Epic Member 5+ Years 1000 Posts Platinum Contributor

    You didn't do anything wrong by cleaning the throttle body, it doesn't take much to damage the TPS and about the only way is to manually force the butterfly open before it is properly disconnected from the vehicle. You take a gamble buying a used one yes, If the person who took it off forced the butterfly open while it was still connected than yes it would have the same problem. I don't know what a new one would cost, I know I can get a new BBK unit for my 05' for $299.

    Before replacing anything you seriously need to check the TPS voltage, and the IAC steps to see what is going on to properly troubleshoot it.
  9. GM Customer Service

    GM Customer Service Rockstar 4 Years 500 Posts

    I would have to agree that your best bet would to have the vehicle looked at. Please keep me posted. Thank you.

    Tricia, GM Customer Service.
  10. My buddy that owns the repair shop brings up a good point .... If it does require a re-learn, then why is this problem of not staying started only happening sporadically and not EVERY time? It can literally go for 2 days and start and run without a problem ... and then all of a sudden not want to stay running at start-up. If indeed the system's "knowledge" of throttle position was "damaged" by my opening and closing it, and it required a "relearn" to "teach" it the proper settings again, wouldn't it use that (incorrect) "knowledge" every time you turned the key?

    My buddy seems to think the problem may lie in the air-flow-meter. Since the problem is sporadic, it could be a damaged sensor wire .... thinking of trying to borrow one from my auto wrecker buddies and see if it cures my woes .... he has told me the next time it acts up, to disconnect the plug going to the air-flow-meter. This automatically puts the system in "safe" mode, and will allow the car to idle, but not accelerate. If it starts right up and idles after disconnecting the plug, then it should point to a bad air flow meter ...

    I'll be sure to post and keep every informed as I wade my way thru this quagmire of electronic BS ... I just remember why I like hot rods so much .... double-pumper Holleys are SO much easier to trouble-shoot ...

    PS ... NONE of this explains the oil in the intake boot, by the way ... one mystery at a time I guess ...

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