idle issue
Thread Starter
Racer
Joined: Dec 2005
Posts: 295
Likes: 0
From: Kempner Texas
idle issue
Car idles great as long as it is over 1000 rpm, but i want to get it right and this is what I've done so far: Set base timing (as best as I could get it the way it was idling) to 6*BTDC. Installed new ACDelco IAC set at 1 1/8", TPS=.59, Fuel Press=40psi, then I went through the low idle procedures of: Key off IAC plugged in, jumper a+b in ALDL, EDIT: key on, wait 30 secs then disconnect IAC, remove jumper, start and run to operating temp. This is where the problem comes in, it just won't idle at anything less than 800rpm, keeps dieing, said screw it and plugged IAC back in and restarted the car and now have the low idle screw cranked in to keep it idling at about 1100 rpm. Idles great there but it ain't right.
What am I doing wrong? Any suggestions?
Thanks
What am I doing wrong? Any suggestions?
Thanks
Last edited by robs87vette; Jan 8, 2006 at 02:55 PM.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
If The IAC pintle was all the way extended (putting it into the diagnostic mode does that) when you unplugged the IAC, then chances are you have a vacuum leak. You should kill the engine when you adjust the throttle plates closed. The engine is getting air from some, unintended source.
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RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
NO! That is NOT what I'm saying. The minimum air adjustment is to be made with the engine running. My point was that IF there weren't an unknown additional source of air, you could have easily idled it down below 400 rpm and killed the engine, while you were doing the adjustment, and not had to settle for an 800 rpm minimum air adjustment that is higher than the warm curb idle spec. What I AM saying is find and fix the vacuum leak.
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RACE ON!!!
Thread Starter
Racer
Joined: Dec 2005
Posts: 295
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From: Kempner Texas
I was thinking more along the lines of valves being too tight, since it will idle smooth at rpm's above 1000 and I have had it idling at 800rpm but at 800 it lopes alot between 700 and 800 then at times it will jump to 1000 and then drop back to like 500 and almost die then somewhat smooth out to 700 and 800 or 900 again
Advanced
Joined: Aug 2004
Posts: 95
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From: Greenville S.C.
I'm having the exact same problem with setting a friends idle, except i havn't replaced or cleaned the IAC. The engine starts to hunt for idle then die at about 800-850 rpm in park. So i set it to 900ish in park, plug the IAC back in, and it goes right back to 1100-1200 in park and 1000-1100 in gear.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by robs87vette
I was thinking more along the lines of valves being too tight, since it will idle smooth at rpm's above 1000 and I have had it idling at 800rpm but at 800 it lopes alot between 700 and 800 then at times it will jump to 1000 and then drop back to like 500 and almost die then somewhat smooth out to 700 and 800 or 900 again
Originally Posted by SkankZilla
So i set it to 900ish in park, plug the IAC back in, and it goes right back to 1100-1200 in park and 1000-1100 in gear.
RACE ON!!!
Thread Starter
Racer
Joined: Dec 2005
Posts: 295
Likes: 0
From: Kempner Texas
Yeah I was talking to someone else and they suggested that due to the cam (zz9 from TPIS) and stock chip I may need to run it a bit higher than the stock idle speed.
I don't have a vaccum leak, I'm pretty sure!
Thanks anyways
I don't have a vaccum leak, I'm pretty sure!
Thanks anyways
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Thread Starter
Racer
Joined: Dec 2005
Posts: 295
Likes: 0
From: Kempner Texas
Originally Posted by SkankZilla
ECT sensor? sorry i'm still learning.
Let me give specs on mods:
Superram U/L, AFR 195's, LPE 219, LT's no cats, gutted smog pump.
Let me give specs on mods:
Superram U/L, AFR 195's, LPE 219, LT's no cats, gutted smog pump.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
You jumped in here with little to no back ground info. Most years have different sensors for the gauges and the ECM. Therefore the reading on the gauge has nothing to do with what the ECM "sees". No C4 adjusts the air/fuel ratio according to the oil temp. Speaking of C4s... Do you realize you are posting in the C4 section? Your profile says your Corvette is a 2000.
RACE ON!!!
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by robs87vette
Yeah I was talking to someone else and they suggested that due to the cam (zz9 from TPIS) and stock chip I may need to run it a bit higher than the stock idle speed.
RACE ON!!!
Thread Starter
Racer
Joined: Dec 2005
Posts: 295
Likes: 0
From: Kempner Texas
Originally Posted by CFI-EFI
You jumped in here with little to no back ground info. Most years have different sensors for the gauges and the ECM. Therefore the reading on the gauge has nothing to do with what the ECM "sees". No C4 adjusts the air/fuel ratio according to the oil temp. Speaking of C4s... Do you realize you are posting in the C4 section? Your profile says your Corvette is a 2000.
RACE ON!!!
RACE ON!!!
Thanks for your time and effort
Last edited by robs87vette; Jan 8, 2006 at 09:41 PM.
Melting Slicks
Joined: Aug 2003
Posts: 3,378
Likes: 388
From: Lakeville MI
Let me guess, you have a gutted MAF too.
I bet it is a mixture problem. All of my idle issues went away after re-scaling the MAF table in the idle airflow region.
Get some scan data to see the MAF flow and what the IAC is doing.
I bet it is a mixture problem. All of my idle issues went away after re-scaling the MAF table in the idle airflow region.
Get some scan data to see the MAF flow and what the IAC is doing.