Why is my idle surging?
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,270
Likes: 0
From: Rockford IL
Why is my idle surging?
I recently had my car tuned with LS1 edit, and got everything pretty well straightened out, but for some reason my idle is surging. It goes from 900 rpm's to 1300 rpms, and back down while sitting in park, any ideas? The car has a 422 with ported MAF and TB, 43 lb injectors, .615 lift cam, and 12:1 compression, so I know its not going to idle perfect, but would like to get rid of the surging. Thanks !
Racer
Joined: Dec 2001
Posts: 288
Likes: 0
From: Houston Tx.
Re: Why is my idle surging? (kwik8racr)
My car is doing the same exact thing but it has a 382 with 237/242 cam, ported MAF, and 30 lb injectors. The car is even surging from the exact same rpm's as yours. My computer was sent to Ed Wright at Fastchips and the shop that originally sent the computer to him was kind of unexperienced so they set my idle at 850. The car was idling very low, it sounded like the car wanted to turn off. Well, the shop that sent the comp went out of business so I personally sent the comp back to Ed and asked for the idle to be set at 900. When I get it back I'll see if it needs to go higher. I don't know if that is going to fix the surging problem though. I can't stand it!!!! I know this didn't answer your question but at least you know your not alone. I would also love to find out why my car is surging so bad too.
:confused:
:confused:
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,270
Likes: 0
From: Rockford IL
Re: Why is my idle surging? (6500RPM)
We had mine set at 800 rpm's at first, and it kept seeming like it wanted to die, so we raised it to 1000,which may be a little high, but it seemed to like it, I just dont know why the surging, it is very aggrevating!
Racer
Joined: Oct 2001
Posts: 483
Likes: 0
From: Downingtown PA
Re: Why is my idle surging? (kwik8racr)
I have the same thing. It's most noticeable when I run the car for a bit, shut it down and start it again. It usually lasts less than 30 seconds and then calms down to a normal idle at about 900 rpm. I'll bet somebody has figured this one out.
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,270
Likes: 0
From: Rockford IL
Re: Why is my idle surging? (01C5fan)
I have the same thing. It's most noticeable when I run the car for a bit, shut it down and start it again. It usually lasts less than 30 seconds and then calms down to a normal idle at about 900 rpm. I'll bet somebody has figured this one out.
Melting Slicks
Joined: Aug 2000
Posts: 2,248
Likes: 1
From: Newland US
Re: Why is my idle surging? (kwik8racr)
kwik8racr,
Well, I'll throw out a thought. I don't know if this is the problem or not, but you might check it out.
If the surging is only occuring for a short time at start up, maybe it is because the charcoal vapor cannister is being purged and dumping vapor into the intake manifold. As soon as the purge is complete, then the idle settles down.
I guess you could check it by unplugging the vapor purge solenoid (just for diagnostics) and start the engine, if the idle is OK, then maybe this explains the surging at start up. If the problem is still there....keep searching.
Good luck.
Mark
I have the same thing. It's most noticeable when I run the car for a bit, shut it down and start it again. It usually lasts less than 30 seconds and then calms down to a normal idle at about 900 rpm. I'll bet somebody has figured this one out.
I wouldn't mind it so bad if it only did it for a few seconds and then stabalized, but it doesn't go away. :confused:
I wouldn't mind it so bad if it only did it for a few seconds and then stabalized, but it doesn't go away. :confused:
If the surging is only occuring for a short time at start up, maybe it is because the charcoal vapor cannister is being purged and dumping vapor into the intake manifold. As soon as the purge is complete, then the idle settles down.
I guess you could check it by unplugging the vapor purge solenoid (just for diagnostics) and start the engine, if the idle is OK, then maybe this explains the surging at start up. If the problem is still there....keep searching.
Good luck.
Mark
Melting Slicks
Joined: Aug 2000
Posts: 2,248
Likes: 1
From: Newland US
Re: Why is my idle surging? (kwik8racr)
kwik8racr,
I'm too lazy to dig out my service manuals right now, so maybe you know. Does the LS1 have an idle air control motor like the LT1? The pintels in those things used to hang up and cause idle problems quite a lot.
Mark
[Modified by MDT, 4:04 PM 9/14/2002]
I'm too lazy to dig out my service manuals right now, so maybe you know. Does the LS1 have an idle air control motor like the LT1? The pintels in those things used to hang up and cause idle problems quite a lot.
Mark
[Modified by MDT, 4:04 PM 9/14/2002]
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Thread Starter
Drifting
Joined: Mar 2001
Posts: 1,270
Likes: 0
From: Rockford IL
Re: Why is my idle surging? (Old Rotor Head)
I have been told by several people to drill a small hole in the TB blade, and this helps reduce the surging, anyone have an idea how big of a hole I should drill?
Safety Car
Joined: Jun 2002
Posts: 3,689
Likes: 1
From: St Petersburg FL
St. Jude Donor '07,'13
Re: Why is my idle surging? (kwik8racr)
The hole in the throttle plate will work but it won't fix the problem properly. The reason why it's surging is because of the increased cam dynamics. The motor is sucking more than the throttle plate can let air in. The correct way is to adjust the air/fuel ratio at idle with the E.C.M. with a lap-top if available. I believe Lingenfelter also sells a throttle body that is modified to let in more air at idle. Lingenfelter would be the first I would call for advise since he does wonders with the LS motors. :cheers:
Melting Slicks
Joined: Feb 2002
Posts: 2,290
Likes: 1
From: Ca
Re: Why is my idle surging? (VBP)
The hole in the throttle plate will work but it won't fix the problem properly. The reason why it's surging is because of the increased cam dynamics. The motor is sucking more than the throttle plate can let air in. The correct way is to adjust the air/fuel ratio at idle with the E.C.M. with a lap-top if available. I believe Lingenfelter also sells a throttle body that is modified to let in more air at idle. Lingenfelter would be the first I would call for advise since he does wonders with the LS motors. :cheers:
This is your computer trying to adjust to your new cam. Your computer has a particular A/F ratio range it can adjust between at idle. The hole in the throttle body tricks the computer and leans out your idle but definatly is not a perminent fix. If you had it tuned with LS1-edit then you need to do more than just raise the idle...you need more air at idle. For those who only see this surging for a few sec's then the computer works it out...this is normal with bigger cams and is corrected with custom tuning. :yesnod:
