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1987 Chevy Cavalier 2.0L auto. Back fire through TBI. high idle.

I have a 1987 cavalier that idles excessively high. it will not idle back down until I am at a complete stop and even then it seems high to me. Also under normal depression of the gas pedal on acceleration I get a stutter and backfire through the TBI all the way to the breather element.
I replaced the AIC in hopes that was the problem but it did not fix a thing.
Will a MAP or TPS do this ?
I have cleaned the injector, as well as the port in the TBI leading to the injector that is what I assume to be coming from the pulsator regulator diaphram or some thing like that ?
Any insight woul dbe appreciated. This is unfortunately, my daily driver for now so I need her in tip top again fast for work.
Thank you !

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  • 4 more comments 
  • vbolton1 May 17, 2009

    I've thought about a brake booster leak as well.
    Hope that isnt the problem. That's a potentially expensive fix. :(

  • vbolton1 May 17, 2009

    Where do they commonly leak from on the booster if that would be the problem ? Probably within the welded pot huh ? :(

  • vbolton1 May 31, 2009

    I'll give that a shot in the morning.
    I tried replacing the IAC ( good used JYD part for cheap ), MAP sensor ( new, didn't solve it, took it back. ), and the TPS ( didn't solve it but I left the new on because its a more common part to fail anyway due to the heat so what the heay ya know.)
    If plugging the booster line doesn't yeild a result I fear it may be the computer. :( Thats only $90 some thing though but still ...


  • vbolton1 May 31, 2009

    No mass air flow sensor on this model but there is a mass air flow sensor relay.
    WTF ! LOL! No mass air but it has a mass air flow relay ?
    That makes a lot of sense. No air Charge sensor either.
    Just pressure/temp sensor in the intake tube just before the TPI, MAP sensor, TPS, EGR, fuel pressure regulator in front of the inmjector mounted on the TPI, Pulse damner ( or something like that ) mounted on the fire wall directly behind the TPI, o2 sensor, speed sensor, AIC motor, oil, and temp sensors, cam shaft position sensor, and knock sensor.
    I think thats it as far as sensors.

  • vbolton1 Jun 01, 2009

    Plugged the booster vac up and nothing. High rev when disconnected just before plugging though as you would expect though right ?
    I bought and installed a complete TBI gasket kit because they all looked as if they have been seeping a little. Cleaned her out real well and put her back together with new gaskets and diaphram. No change.
    What about a cam sensor ? Since this is seemingly a timing advance issue would a bad cam sensor give me a sputter when to much pedal is applied ?
    How about a fuel filter or fuel pump ?

  • vbolton1 Oct 09, 2009

    I found the problem (S) relating to the stutter and back fire. Bad IAC, faulty plug wires and plugs.
    Still; need to replace the IAC.

    Now I get a low idle ( almost a stalling condition )
    In reverse and when I 1st place her in drive. Found that to be a bad TCC solenoid.

    I'll be busy this weekend LOL !
    Thank you !




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  • 532 Answers

Try unplugging the brake booster vacumm line and cap the line to see if this helps.make sure the throttle is against the stop where it hits the set screw for the idle,but dont try to adjust it,its at a factory setting.

Posted on May 17, 2009

  • scott May 17, 2009

    just behind the master cylinder there is 1 seal,and 1 inside the vehicle behind the brake pedal,brake boosters rebuilt arent too expensive,plug the line first so you dont have to waste money.Process of elimination without buying parts is cheaper if you dont count your time.

  • scott May 31, 2009

    i thought about it for a while,does that car have a mass aif flow sensor in the air breather?im not sure,i havent worked on a 2.0 litre cavalier in so long,i forget how they are designed.If it does then check it for debree on it like white fuzz which is from the air breather element.When that happens it doesnt get the correct reading for how much air is entering the throttle body,and it will spit and sputter when accelerating.That is more typical with 3.1 litre-3.3 litre GM engines.Try that maybe thats the problem,reset the computer.Hope this helps..



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While looking at the engine from in front of the car with the hood up..
Locate the TBI assembly ( follow the air intake tub from the cor support back. It leads directly to it ). Next look on the lower left side of the TBI just above the throttle linkage connection to the TBI.
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