5.7 TBI - high idle

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gwhiz

Greasemonkey
Aug 21, 2012
184
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EdontheBeach said:
looks like i jumped the gun - i took the car out to run a few errands, within 5 mins. of leaving the house it was back to it's old way. 1200-1300 for 30-40 seconds when i come to a stop.
i would get a multimeter and check the tps.did you clean out the entire throttle body?make sure the throttle plates open and close smoothly,no sticking or binding.
 

EdontheBeach

Master Mechanic
Feb 29, 2012
278
176
43
Indian Rocks Beach, FL
fellas - you'll need to school me on checking/setting the tps. i thought i did a thorough job cleaning up the throttle body, but tomorrow i'm going to disconnect the battery again (and scrub down the throttle body again), let it reset and give it another try.

i don't think the CC is pulling since it is off - but i will disconnect it from the throttle body just to be sure.

thanks again for the help, TBI is gonna have a learning curve for me, i've always had carbs.
 
Oct 14, 2008
8,806
7,746
113
Melville,Saskatchewan
There should be a wire with approximately 5 volts key on, a ground wire and the signal wire. Moving the throttle arm it should read around .5 volts at idle to 4.5 volts full throttle. Move it up and down and make sure the voltage raises and lowers. Make sure the ground wire isn't open too.
 

Dennyboy

Master Mechanic
Jun 26, 2011
387
0
16
Minnesota
possible small vacuum leak maybe or sticking injector bad tps signal maybe
 

turboaudi

Not-quite-so-new-guy
Jan 27, 2013
35
0
6
upstate NY
can you hook a scan tool to it that is the only way to correctly fix problems like this if not you can cut the connector from another car & wire it in coolant temp will cause hi idle also if the swap has no speed sensor wired in it can never learn the iac counts it has to see a steady speed above 45 mph to learn this was a big problem in many swaps you also need a switch on your trans or shifter to tell the computer if you are in park or drive unless you have a 4l60e trans if not you can use the switch from 88-91 chevy trucks it fits on gbody columns . you can tell if you already have these if you scan it will have speed / gear position data shown dave
 

EdontheBeach

Master Mechanic
Feb 29, 2012
278
176
43
Indian Rocks Beach, FL
i think i have it figured out - the butterfly will not close without 30 or 40 secs or my fingers making it close. the previous owner had installed extra return springs as a cure, without success. i think i will need to disasemble, soak and re assemble. i believe there is just some gunk down there i can't get to with a toothbrush and carb cleaner.
 

gwhiz

Greasemonkey
Aug 21, 2012
184
0
0
EdontheBeach said:
i think i have it figured out - the butterfly will not close without 30 or 40 secs or my fingers making it close. the previous owner had installed extra return springs as a cure, without success. i think i will need to disasemble, soak and re assemble. i believe there is just some gunk down there i can't get to with a toothbrush and carb cleaner.
I had same problem,drove me crazy.check for excessive play in the throttle shaft,those are known to wear out and cause air to leak pass them kinda like the old quadrajets did.If to much play I would get another one from the junkyard.
 

tc1959

Comic Book Super Hero
Dec 23, 2009
3,963
1,975
113
Surprise AZ.
EdontheBeach said:
i think i have it figured out - the butterfly will not close without 30 or 40 secs or my fingers making it close. the previous owner had installed extra return springs as a cure, without success. i think i will need to disasemble, soak and re assemble. i believe there is just some gunk down there i can't get to with a toothbrush and carb cleaner.
If the bushings are worn you can take it to a carb shop and have new bushings installed.
 
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