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Engine wants to die with a little pedal (350tbi)

Discussion in 'Truck & Equipment Repair' started by Banksy, Jan 14, 2013.

  1. Banksy

    Banksy PlowSite Veteran
    Messages: 3,113

    My Chevy has a small throttle issue. It starts just fine and idles fine (with what feels like a small bump or misfire some times, very slight). If I lightly give it just a little throttle, the engine starts to stall and sputter, but doesn't die and this is in Park or Drive. If I floor it, it doesn't do it at all. There is just that initial spot and after that it's fine.

    Ideas?
     
    Last edited: Jan 14, 2013
  2. Banksy

    Banksy PlowSite Veteran
    Messages: 3,113

    It barely takes 3 revolutions to fire up. Just thought I'd add that.
     
  3. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,971

    Assuming its only when its cold ??
     
  4. Banksy

    Banksy PlowSite Veteran
    Messages: 3,113

    Yes when cold. Can't remember when hot. I'll warm it up and check.
     
  5. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,971

    Ok. 2 of ours do it,,,,honestly I just tell the guys to warm them up. If I ever get time or really care I was Gunna look into the cap and rotor area but not top on my priority list
     
  6. Banksy

    Banksy PlowSite Veteran
    Messages: 3,113

    I just went out and let it warm all the way up and it pretty much goes away. Couple times there was a very slight hiccup, but maybe it's just 23 year old 1990's technology. Never owned a TBI before, so I guess I'll just have to get used to it's quirks. I don't even have it on the road yet, so I don't know all it's little quirks yet.
     
  7. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,971

    Ok....maybe someone else might chime in and say something else
     
  8. T-Trim

    T-Trim Senior Member
    from NE OH
    Messages: 207

    I would check the egr valve. I had a 92 k-5 that did the same thing. Once I replaced it. good at new. If you like I can check on "how to check a egr" just pm and have it att mike . we have three other people in ther company using the same log in.
     
  9. Banksy

    Banksy PlowSite Veteran
    Messages: 3,113

    Does my truck even have an EGR??
     
  10. T-Trim

    T-Trim Senior Member
    from NE OH
    Messages: 207

    Its between the upper rad hose and the TB. Its bolted to the manifold.
     
  11. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,114

    Throttle position sensor, mass air flow sensor.
    I suppose it *could* be the EGR, but I doubt it. I had a really bad EGR in a TBI Nissan (stuck wide open), never hesitated, just ran rough.
     
  12. Holland

    Holland Senior Member
    Messages: 605

    No maf on a tbi. They are speed density.

    I would start out checking the coolant temp sensor. Remember tho, there are two on this engine. One up by the t stat is for the ecm, other is for the gauges. Get ahold of a scanner and see what temp its reading.

    Any questions at all hit me up. Thumbs Up
     
  13. jasonv

    jasonv PlowSite.com Addict
    from kannada
    Messages: 1,114

    Hard to keep up with all the brands and what they like to call all the different parts that are really the same. On my Nissan, they called the part between the injector body and intake manifold the MAF. Whatever it is being called, it tells the thing how much air is going through. If that isn't working right, it will provide the wrong mix and timing.
     
  14. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,971

    Well,,,gm ain't a Nissan. Tbi is real primitive. Hardly any sensors compared to now adays
     
  15. Holland

    Holland Senior Member
    Messages: 605

    No offense, but if you dont know the vehicle the op is talking about then how are you going to help him?
     
  16. theholycow

    theholycow PlowSite.com Addict
    Messages: 1,180

    EGR was my first thought. While the EGR valve on my car, fully actuated, is incapable of stalling my engine, others can certainly stall other engines under certain conditions.

    MAF is Mass Air Flow, it measures air by mass (weight). This system does not use any measurement of how much air is going through, neither by mass nor by volume. It uses MAP, Manifold Absolute Pressure. It calculates (rather than measures) how much air moves through based on air pressure in the intake manifold and RPM. (Side note: Systems equipped with the MAF sensor usually/always also have the MAP sensor but don't use it in the same way except if the MAF fails.)
     
  17. Banksy

    Banksy PlowSite Veteran
    Messages: 3,113

    I had a 351w carbed 1986 F250 and that thing would act just like this truck when it was cold. A TBI is really a fancy carb, in a manner of speaking.

    A new temo sensor and tps are el cheapo on rockauto.com.
     
  18. Snowzilla

    Snowzilla Senior Member
    from Iowa
    Messages: 397

    The TBI may have been primitive, but my experience was it was very reliable. I had an '89 5.7L which is still running for a new owner. It would stall and left me stranded a few times. The solution for me was replacing the distributor. Maybe a shop could rule out ignition with diagnostics. I can't recall if the distributor had a vac advance on it. But may be something to check, cracked line,etc.

    I recall a few hiccups here & there at idle but I excused it as old age.
     
  19. T-Trim

    T-Trim Senior Member
    from NE OH
    Messages: 207

    did you figure it out?
     
  20. matzke3

    matzke3 Member
    Messages: 50

    Those dist do not have any vac control. If the engine totally dies at idle and restarts just fine its usually the dist. I've had several of these tbi trucks and most of them with the 747 ecm (likely what you have) and an AUTO trans prom do that. It seems those programmed with a manual do not. I'm trying to program that out of my project plow truck (400 built tbi). I think it is a sag in the timing curve. Meanwhile I suggest resetting the timing to 0 degrees with the brown/white wire connector unhooked, and or finding an ecm or prom for a manual trans.