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Old 06-01-2008, 11:11 AM   #1
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Join Date: Feb 2007
Location: Spring, TX
Posts: 489
Car: 91 Bird
Engine: TPI 350
Transmission: 5-Speed
Axle/Gears: 2.77 posi

Classifieds Rating: (1)
idle fluctuation problem - Comp Cam too big?

fluctuates at idle but NOT with a/c on. With A/C on it is just fine. A/C off it fluctuates. SES is showing no codes.

adjusted IAC to 450 then plugged it back in. it idled different with IAC. SO it is doing something - but maybe not the right thing.

adjusted TPS to .54 at idle and it is at 4.38 WOT. Seems to be smooth going up from idle to wot.

IAC is about two years old. Seemed to work well during that time.
TPS is about 1.5 years old but sitting up the whole time on an engine - never used.
Timing is about at 10 deg advanced without ecm
5-speed manual
=======================================================
new engine swapped in - 350 TPI (now has 30 miles on engine). was 305 TBI. changed wire harness and ecm. I double checked the ecm it was for a 1989 350 TPI with a MAF.

cam - Comp Cams CS XR258HR-10
Int 258 exh 264
duration @ .05 206 212
valve lift .480 .487
lobe sep 110

flat top pistons - 4 valve relief. 0.020 over
========================================================
other than the idle it runs fine. very smooth acceleration.

Thanks for the help.
__________________
-1991 Firebird 350 TPI, 5speed, 2.77 posi, 4 wheel disc,.
-1978 Bonanza Ed. Blazer, Cummins 4BT, NV4500, NP205, 14bff, D60, 4 wheel disc.
-1970 Camaro RS

When you care enough to shoot the very best.

Last edited by FNFAL308; 06-01-2008 at 11:17 AM.
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Old 06-01-2008, 07:12 PM   #2
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Join Date: Feb 2007
Location: Spring, TX
Posts: 489
Car: 91 Bird
Engine: TPI 350
Transmission: 5-Speed
Axle/Gears: 2.77 posi

Classifieds Rating: (1)
Re: idle fluctuation problem - Comp Cam too big?

Any guesses? MAF? IAC? TPS? WHat would you bet on?

This is my first roller cam engine, first TPI, first with MAF, so I would like opinions.

I know the cam is not really that big but I don't know at what point the idle will be affected

Thanks!
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Old 06-01-2008, 09:49 PM   #3
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Join Date: Feb 2007
Location: Spring, TX
Posts: 489
Car: 91 Bird
Engine: TPI 350
Transmission: 5-Speed
Axle/Gears: 2.77 posi

Classifieds Rating: (1)
Re: idle fluctuation problem - Comp Cam too big?

well - the problem was the wrong IAC.
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Old 06-01-2008, 09:49 PM
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