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high idle on startup / revs stick?

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Old 03-08-2019, 10:35 PM
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Default high idle on startup / revs stick?

So quick question as im not familiar with these motors, as much as I am with my 5.7L in my Burb... on the 92 Bravada Vin Z (4.3L TBI) that I have, it revs high on start up, say 11-15, and then eventually calms down. When you step on the pedal to rev it up or hit it from under the hood, it seems to hold the rev a little, and the cable seems to be fine, and not stuck so to say. Im not sure where to start if its TPS, IAC, ECT, or something else I may be missing... It seems to be all there and other than that, it drives fine, just have to barely push the pedal to get small amounts of gas, otherwise itll take off or rev high

Thanks
 
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Old 03-10-2019, 04:34 AM
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Is it revving high only on cold starts?
And when it warms up the rpm starts to reduce?

To see 1100 rpm on cold starts looks normal to me. It should start to drop within about 20 - 30 seconds and gradually reduce to normal idle around 600 - 800 rpm.
Depending on the outside temperature and the engine temperature it may take longer.
 
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Old 03-10-2019, 07:39 AM
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Originally Posted by error_401 View Post
Is it revving high only on cold starts?
And when it warms up the rpm starts to reduce?

To see 1100 rpm on cold starts looks normal to me. It should start to drop within about 20 - 30 seconds and gradually reduce to normal idle around 600 - 800 rpm.
Depending on the outside temperature and the engine temperature it may take longer.
itís on both cold and warm starts... itís odd because just at idle itíll rev normally whether itís cold or warm, but when you give it gas the smallest touch at the pedal sends it to 1500-2000, and itíll hang at that rpm for a sec as if the pedal is being held there
 
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Old 03-14-2019, 03:59 AM
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Is it revving up to that 1'500 - 2'000 rpm in Neutral or as well when in gear? (Careful that is quite some acceleration)

If it does this in neutral (no gear in) the accelerator cable pullers etc. could be stuck. Check the whole accelerator mechanism.
Starting at the gas pedal checking it is not interfering with the carpet etc. Check with somebody pushing it that on the TBI it returns to the stop.
Check the additional pulling mechanism from the cruise control. It all has to operate smoothly.

Why would I start with that? Because IMHO 1'500 - 2'000 rpm is so high that I suspect the throttle body has to be opened and not returning to the stop smoothly.

When you are at it check all the vacuum lines from the TBI for cracking, holes damage by scuffing etc. When the engine runs there should be no hissing from these lines.
This is an additional source of high idle but would give slightly different symptoms such as being high all the time.
 
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