Questions about Throttle Body TPS & IAC
Thread Starter
Joined: Jan 2001
Posts: 3,188
Likes: 59
From: Conroe, TX
Car: 1987 GTA
Engine: LS1
Transmission: 4L60e
Questions about Throttle Body TPS & IAC
Car: 1987 GTA L98
Modifications: exhaust, airfoil, 88 serpentine setup
I just finished cleaning my throttlebody out, including the IAC passage. My car has had a bad idle for a while now (since the wreck) and often dies at stoplights because it idles WAY low (about 400-500 rpm). While it is strugling it seems to miss and eventually die if no gas is given. The car runs fine besides that.
I put my IAC and TPS back on and with the IAC unplugged (to set the idle to 450 ~ the tech article), I can't even get the idle to go under about 1300 rpm. I can pull the screw so far back that it won't idle any lower. Now I don't own a functioning voltmeter and have suspicions that the TPS is the culprit. I've adjusted it up and down and there is little to no change. Can anybody shed some light on this situation?
Thanks,
Jon
Modifications: exhaust, airfoil, 88 serpentine setup
I just finished cleaning my throttlebody out, including the IAC passage. My car has had a bad idle for a while now (since the wreck) and often dies at stoplights because it idles WAY low (about 400-500 rpm). While it is strugling it seems to miss and eventually die if no gas is given. The car runs fine besides that.
I put my IAC and TPS back on and with the IAC unplugged (to set the idle to 450 ~ the tech article), I can't even get the idle to go under about 1300 rpm. I can pull the screw so far back that it won't idle any lower. Now I don't own a functioning voltmeter and have suspicions that the TPS is the culprit. I've adjusted it up and down and there is little to no change. Can anybody shed some light on this situation?
Thanks,
Jon
Thread Starter
Joined: Jan 2001
Posts: 3,188
Likes: 59
From: Conroe, TX
Car: 1987 GTA
Engine: LS1
Transmission: 4L60e
well - i goofed. I searched around and found this by irocster:
Followed that (which was probably what the tech article said...it's been a long day).
HOWEVER my idle is still choppy and I suspect it has something to do with my brake booster causing a vacuum leak. Would a vacuum leak cause my idle to be choppy?
Alright, tell me if this is right:
Jump A and B with paper clip, turn on ignition, wait 30 seconds, unplug IAC, turn of ignition, unplug jumpers, start engine, adjust to 450 rpm, turn off engine, re-connect IAC, start engine, turn off after checking idle (@ 650), turn on ignition and re-set TPS, turn ignition off, unplug battery for 10 minutes.
Jump A and B with paper clip, turn on ignition, wait 30 seconds, unplug IAC, turn of ignition, unplug jumpers, start engine, adjust to 450 rpm, turn off engine, re-connect IAC, start engine, turn off after checking idle (@ 650), turn on ignition and re-set TPS, turn ignition off, unplug battery for 10 minutes.
HOWEVER my idle is still choppy and I suspect it has something to do with my brake booster causing a vacuum leak. Would a vacuum leak cause my idle to be choppy?
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From: Dallas, TX area
Car: 91 Formula WS6 (Black, T-Tops)
Engine: 383 MiniRam (529 HP, 519 TQ - DD2K)
Transmission: Built '97 T56, Pro 5.0, CF-DF
Axle/Gears: 4.11 posi Ford 9"
ABSOLUTELY!!! In fact, that's the usual/most likely cause of a "choppy idle".
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Joined: Sep 2002
Posts: 984
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From: Nebraska
Car: '89 Formula
Engine: 355
Transmission: 700R4
Axle/Gears: 9 bolt
ABSOLUTELY!!! In fact, that's the usual/most likely cause of a "choppy idle".
Pull the vacuum line off the brake booster and plug it, if the idle smooths out youve found your problem
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