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Author Topic: TBI high idle  (Read 4925 times)

Offline captain carnage

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TBI high idle
« on: December 09, 2010, 06:06:33 pm »
So in my blazer is a TBI 350 and it idles very high. I'm pretty sure the idle is factory set and can't be messed with ??? Am I wrong? Or is there something I can do to bring the idle down to normal? Could there be another issue causing this? Thanks,

Chris,
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Offline Da67goatman

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Re: TBI high idle
« Reply #1 on: December 09, 2010, 06:11:00 pm »
I played with my timing on my tbi and it always returned to the same idle, i would reset the ecu, just unplug it for a couple secs and see if it resets.
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<Pitcrew>
1989 R2500 Suburban mild 350 TBI 700r4 10.5" 14bolt 4.10 w/ 33s
1992 fullsize Blazer 4x4  35s no lift, 4.10s, Hella driving lights, TJ Flares, Huge bumpers, Snorkel, custom interior

Offline captain carnage

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Re: TBI high idle
« Reply #2 on: December 09, 2010, 06:22:52 pm »
Thanks for the quick reply, I'll give it a try.
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Offline topp

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Re: TBI high idle
« Reply #3 on: December 09, 2010, 07:00:00 pm »
To adjust the timing you need to disconnect the Brown striped wire near the master cylinder, start engine,then time it, then shut off, then reconnect the wire.

High idle is usually a vacuum leak on the TBI's....Spray carb cleaner around all vacuum lines and any mating surfaces with gaskets...

Any change in idle, you found the leak...
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'90 Suburban TBI 350

Offline sag4spd

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Re: TBI high idle
« Reply #4 on: December 10, 2010, 02:04:56 pm »
TBI's are known for their base gasket leaking.  This is the gasket that seats it to the intake manifold.
Disconnect all linkage and vac. lines. Loosen and remove fuel and return line- Dont lose little brown o-rings!  Disconnect all compter lines- Carefully remove injector electrical lines.  Unbolt three 13mm bolts. remove unit. scrape old gasket and replace.
 Also check and replace any cracked vacuum lines too.  The hard plastic ones crack easily- be careful.
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Offline VileZambonie

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Re: TBI high idle
« Reply #5 on: December 10, 2010, 06:14:26 pm »
Quote
TBI's are known for their base gasket leaking. 


This

Before you replace it just carefully spray a little carb clean around the base of the unit and see if it changes the idle speed.
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Offline 1984k30

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Re: TBI high idle
« Reply #6 on: December 10, 2010, 07:16:59 pm »
Most tbi have a round cover by the linkage that can be removed and you can turn down the idle.  I think it is there so people don't mess with the idle setting.  the cover is the same as what is on a quad jet carb to adjust the air fuel mixture.
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Offline VileZambonie

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Re: TBI high idle
« Reply #7 on: December 10, 2010, 07:36:32 pm »
You can turn it all the way down and all you will do is cause the IAC to try and compensate.
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              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline captain carnage

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Re: TBI high idle
« Reply #8 on: December 11, 2010, 12:35:30 pm »
Thanks everyone, I still haven't got around to trying anything yet, but i should later today.
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Offline captain carnage

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Re: TBI high idle
« Reply #9 on: December 11, 2010, 08:15:55 pm »
Well I sprayed carb cleaner around the base gasket and the RPMs picked up. I guess I know what I'm doing next ;D Thanks for the help everyone.
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