C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

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Old Dec 24, 2013 | 04:24 PM
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Default More Idle Issues

I had been having problems with my idle being a bit too high (around 850) so I decided to take apart my TB and give it a good cleaning and replace the IAC. Got everything apart, cleaned the TB, put in a new IAC (from napa), put everything back together, did the IAC reset procedure, reset the TPS voltage to .54. Car was running pretty damn well with idle at around 600, and nice and smooth. Ran well for about 2 days. Today, started up fine, drove about a mile to the store, and turned it off. When I got in to head home it started fine, but idle immediately dropped to around 350 and was really rough, and smelled very rich. Limped it home, and sitting in the driveway it would continue to either idle really high, or really low, still smelling rich.

I feel that this can't just be a coincidence and must be related to my recent repairs... What did I mess up during my TB repair?
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Old Dec 24, 2013 | 04:40 PM
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Did you do a minimum idle adjustment?

http://forums.corvetteforum.com/1570563689-post1.html
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Old Dec 24, 2013 | 04:45 PM
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I would also check for vacuum leak
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Old Dec 24, 2013 | 05:07 PM
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Originally Posted by Cliff Harris
Did you do a minimum idle adjustment?

http://forums.corvetteforum.com/1570563689-post1.html
Yes... followed that exact guide to a T. Only part I had to modify was the minimum RPM. Mine would stall out at anything less than 500. So I set it as low as it would go and idle smooth.

Originally Posted by Kevova
I would also check for vacuum leak
This is the only other thing i can think of. Would that make it run rich though?

Stupid thing is, I just went out to check it again, and to recheck TPS voltage and now it's running fine, idle @ 625 nice and smooth. Let it heat all the way off, shut her down and started up again, still fine. Now I'm even more confused. My car seems to be breaking and repairing itself while I'm away from it.

I don't know if I can trust it now though, and I was taking her for a 40 mile drive for Christmas with the fam tomorrow.
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Old Dec 24, 2013 | 06:39 PM
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Did by some chance you pull a battery cable off somewhere in the process? The car will run funny until the ECM relearns everything.

Check the IAC housing with some carb spray or smoke from a cig (not at the same time!!). There is also a small vac line under the TB that may have gotten knocked loose.

Simple things first.
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Old Dec 24, 2013 | 06:42 PM
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May be a coincidence, but maybe your fuel pressure regulator just blew out and you are sucking raw fuel into the intake. Check the line going to the regulator and see if there is gas in there. Sucking works well here.
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