High idle
Thread Starter
TECH Apprentice
iTrader: (7)
Joined: Mar 2005
Posts: 358
Likes: 0
From: Rancho Cucamonga, Ca
High idle I have searched, but have not found the answer. When I start the motor cold, it idles about 800 rpm or so. That is good for me. But when she gets warm, it idles about 2000 rpm or so. I cant turn the idle down cause at cold starts it wont idle or even start without giving it some throttle. Can I unplug the throttle position sensor and be ok? If so, is it the top or bottom on the throttle body. BTW a 2000 motor with full bolt ons, a T-REX cam, bla, bla bla, and a mail tune. Thanks, Joey
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
don't unplug the TPS sensor (several tables in the PCM reference it... amongst other things it's needed to enter PE)
2000rpm idle sounds like a vacuum leak, have you verified everything's sealed up correctly?
2000rpm idle sounds like a vacuum leak, have you verified everything's sealed up correctly?
I Had The Same Problem But Mine Started After A Head Install. It Ended Up Being In The Tuning. My Tuner Finally Fixed It After About 5 Different Uploads And Some Major Mods In Ls1 Edit
Thread Starter
TECH Apprentice
iTrader: (7)
Joined: Mar 2005
Posts: 358
Likes: 0
From: Rancho Cucamonga, Ca
Originally Posted by DramaFoYoMama
Sounds to me like your IAC effective area table needs to be reworked. Unplug the IAC motor after the car warms up (top plug on the throttle body), and see if it still does it.
If that works, is it bad to leave it unplugged all the time? Thanks.
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo Thread Starter
TECH Apprentice
iTrader: (7)
Joined: Mar 2005
Posts: 358
Likes: 0
From: Rancho Cucamonga, Ca
O.K., uplugged the AIC and still high idle. I have all the vacuum ports caped with vacuum caps. Is there one of them that shoud not be capped? This in an offroad truck that is not street legal, that is why I removed all the smog crap. Any ideas???
TECH Apprentice
Joined: Oct 2004
Posts: 360
Likes: 0
From: Katy, TX
Well, we can rule out that. There's no way for the car to open the blade more if the motor's not plugged in. Do you have a hole in your blade? If so, how big is it? Also, are you sure the blade is not hanging up? If those things are okay, there is either an intake or exhaust leak somewhere.
Thread Starter
TECH Apprentice
iTrader: (7)
Joined: Mar 2005
Posts: 358
Likes: 0
From: Rancho Cucamonga, Ca
DramaFoYoMama, thanks for the input
Well, after searching this site for all options, I came up with the passenger side breathers on the valve covers, the front one needs to be connected to the top front of the trottle body (I think) and the other can be capped. But I still have the oil fill cap and dont really want to pull the valve cover to remove that for a breather, so is the front one to the throttle body enough of a vent? I do have a vent on the driver side where the pcv was.
Right now, I have the tb port capped and the two small ports on the valve cover just has tube with vents on them. After searching, I think I learned that the front one NEEDS to be connected to the tb, right? Would this create the vacuum leak that cause the high idle?
I am going to post this in another thread to see if I can get more responces as this is not a tuning issue. Thanks again, Joey
Well, after searching this site for all options, I came up with the passenger side breathers on the valve covers, the front one needs to be connected to the top front of the trottle body (I think) and the other can be capped. But I still have the oil fill cap and dont really want to pull the valve cover to remove that for a breather, so is the front one to the throttle body enough of a vent? I do have a vent on the driver side where the pcv was.
Right now, I have the tb port capped and the two small ports on the valve cover just has tube with vents on them. After searching, I think I learned that the front one NEEDS to be connected to the tb, right? Would this create the vacuum leak that cause the high idle?
I am going to post this in another thread to see if I can get more responces as this is not a tuning issue. Thanks again, Joey
TECH Apprentice
Joined: Oct 2004
Posts: 360
Likes: 0
From: Katy, TX
That sounds like your problem to me. I doubt it's pulling enough vacuum at idle with the way you have it connected. You could verify this with a scan tool. Do you have all the stock vacuum lines to try it that way? What was your reason to have it connected the way you do? Besides getting rid of your PVC system, maybe I am picturing something incorrectly in my head.
Thread Starter
TECH Apprentice
iTrader: (7)
Joined: Mar 2005
Posts: 358
Likes: 0
From: Rancho Cucamonga, Ca
Originally Posted by DramaFoYoMama
That sounds like your problem to me. I doubt it's pulling enough vacuum at idle with the way you have it connected. You could verify this with a scan tool. Do you have all the stock vacuum lines to try it that way? What was your reason to have it connected the way you do? Besides getting rid of your PVC system, maybe I am picturing something incorrectly in my head.
I do have most of the old stuff, I will try to reconnect the lines to see what happens.
I dont have a diognostic (sp?) port for the scan tool.
There is actually no reason why I connected thing the way I did besides not knowing.......
I figured that it runs, so it must be right 
obviously I am wrong and now trying to fix it. I am thinking these vacuum line could be the culprit. Thanks again 
TECH Apprentice
Joined: Oct 2004
Posts: 360
Likes: 0
From: Katy, TX
Do you have anyone to tune it for you? You could change the values in the Spark ECT table for the temps where you are having issues at. FWIW, I run -5.5 degrees of timing at idle. Yes, that negative sign is there on purpose. 
If you can find someone in your area with EFILive, they can use the live controls to retard spark at idle to see where it wants to be. You can then take these values and plug them into the Spark ECT table. Is the PCm tuned at all? I'd be happy to tune the thing for you, but I'm nowhere near you.
If you can find someone in your area with EFILive, they can use the live controls to retard spark at idle to see where it wants to be. You can then take these values and plug them into the Spark ECT table. Is the PCm tuned at all? I'd be happy to tune the thing for you, but I'm nowhere near you. 
^Wow, I run 35 degrees at idle.
As for the pcv thing, the port on the throttlebody is a fresh air vent (red in the picture), so filtered air goes from the tb to the engine. You need it hooked up but it's not causing a vacuum leak since it's before the throttle blade.
The port behind the throttlebody on the neck of the intake is the pcv line (blue in the picture). If it's unhooked it could be your vacuum leak. Since it's behind the throttle blade it has vacuum and can't just be open to the atmosphere. If you replace it with a breather it should be capped off on the intake side and the valvecover side.
As for the pcv thing, the port on the throttlebody is a fresh air vent (red in the picture), so filtered air goes from the tb to the engine. You need it hooked up but it's not causing a vacuum leak since it's before the throttle blade.
The port behind the throttlebody on the neck of the intake is the pcv line (blue in the picture). If it's unhooked it could be your vacuum leak. Since it's behind the throttle blade it has vacuum and can't just be open to the atmosphere. If you replace it with a breather it should be capped off on the intake side and the valvecover side.
