idle surge? any thoughts?
Thread Starter
Racer
Joined: Nov 2005
Posts: 278
Likes: 0
From: melbourne fl
idle surge? any thoughts?
lately my '98 has been surging a bit at idle. it would got from 600 to about 900 over and over again. i just swapped heads, cam, and manifold and it still does the same except from 900 to 1200 over and over. does anyone have any ideas what this could be? also when i would turn the a/c on the car would nearly die at idle.
thanks,
phillip
thanks,
phillip
Race Director
Joined: Nov 2005
Posts: 14,548
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From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
You are in need of a good tune. When I did my H/C and LG Pros it surged like a biotch. I took it to Synergy for a tune and she runs **** now.
Advanced
Joined: Jun 2003
Posts: 81
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From: Alpharetta GA
Idle Issues
Yup, Almost always the tune. There are several idle settings that could have been missed. AC on and AC off. Rolling Idle and stopped Idle.
You must verify if there are any codes? Check engine light?
Some hardware that should be looked at...speaking from experience!!
Air leaks in the intake, around map sensor, port gaskets and throttle body gaskets, brake vac hose in back, "check valve", and little vac hose on pass side back that could make it run rich and idle rough. (unmeasured air getting in the intake, o2 sensors pick that up and add fuel to the mix) F.A.S.T intakes that have been taken apart won't seal back properly (requires a bead of silicone around the whole thing) Cracked headers, header gaskets, header flanges, bad or damaged o2 sensors or wires can throw it off. Athough unlikely a bad MAF could also add to the problem.
You must verify if there are any codes? Check engine light?
Some hardware that should be looked at...speaking from experience!!
Air leaks in the intake, around map sensor, port gaskets and throttle body gaskets, brake vac hose in back, "check valve", and little vac hose on pass side back that could make it run rich and idle rough. (unmeasured air getting in the intake, o2 sensors pick that up and add fuel to the mix) F.A.S.T intakes that have been taken apart won't seal back properly (requires a bead of silicone around the whole thing) Cracked headers, header gaskets, header flanges, bad or damaged o2 sensors or wires can throw it off. Athough unlikely a bad MAF could also add to the problem.
Last edited by MacC5; Aug 31, 2006 at 07:45 PM.
Life Time NCM #2196
Joined: Sep 2004
Posts: 82,559
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From: Converse TX
Phil, congrlations first on the mods and I would call Corey in the morning and let him know what is going on and have him put your baby back on the dyno for additional tuning as I suspect it only needs a few tweaks and he can also look for some of the other possibilities of the previous post stated
Safety Car
Joined: Mar 2002
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Cruise-In V Veteran
St. Jude Donor '09
Originally Posted by 98TightyWhitey
i had it over there on the dyno on wednesday for a tune and it is still doing it
Fwiw.
Life Time NCM #2196
Joined: Sep 2004
Posts: 82,559
Likes: 1,665
From: Converse TX
Originally Posted by Bink
Idle, and idle transitioning, tuning doesn't require a dyno. It requires refinement of idle tables.........airflow, fuel and timing. The more radical the cam the greater the degree of refinement - in general.
Fwiw.
Fwiw.
Have Corey refine these tables he can do this as he has the program to do this as this is supposed to be part of the tune when on the dyno
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Melting Slicks
Joined: Jun 2004
Posts: 3,458
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From: panama city beach florida USA
St. Jude Donor '09
you had the problem when it was stock you said. i sounds like an air leak.what did ya do before the cam etc . a GOOD scan tool can pin point the problem in a sec by looking at the data while its 'hunting'
Thread Starter
Racer
Joined: Nov 2005
Posts: 278
Likes: 0
From: melbourne fl
Originally Posted by patton
you had the problem when it was stock you said. i sounds like an air leak.what did ya do before the cam etc . a GOOD scan tool can pin point the problem in a sec by looking at the data while its 'hunting'
thanks for your suggestions
phillip
