Update: High Idle Issue Finally Solved
Thread Starter
Joined: Feb 2005
Posts: 716
Likes: 2
From: Minneapolis MN
Update: High Idle Issue Finally Solved I'm putting this here for posterity in case this happens to someone else.
Initial thread
https://ls1tech.com/forums/pcm-diagn...connected.html
Long Version
Last year a completed a LS1 swap into a 2000 BMW 5 series. I topped the LS1 with a LS2 intake and NW 90mm TB. For the wiring, I built one from scratch to that way it fit the car perfectly.
The car ran fine with the exception of a high idle (~2500) It would only idle fine if I disconnected the IAC.
Searching found two other people who had the exact same problem. (see links below)
http://www.hptuners.com/forum/showthread.php?p=247582
http://www.ls1.com/forums/showthread.php?t=110370
(link above appears to be broken)
I spent a year chasing this problem from checking for vacuum leaks, replacing the TPS and IAC. Nothing seemed to help.
Finally I tried to think what is the one common thing between myself and the other two people having this issue? We all had LS1 swaps. With that I figured I should looks into the harness. Mind you I had double checked a year ago and at the time confirmed that my IAC was wired correctly.
Last evening I decided to double check my wiring again and I found that I had switched two wires going to the IAC. The Coil B Hi was going to the Coil B lo and vice versa. I rewired the IAC and the problem has not returned. I have started the car several times now without issue.
Short version
My high idle issue was as a result of mis-wiring the IAC. Two pins were mismatched.Correcting this fixed the issue.
Initial thread
https://ls1tech.com/forums/pcm-diagn...connected.html
Long Version
Last year a completed a LS1 swap into a 2000 BMW 5 series. I topped the LS1 with a LS2 intake and NW 90mm TB. For the wiring, I built one from scratch to that way it fit the car perfectly.
The car ran fine with the exception of a high idle (~2500) It would only idle fine if I disconnected the IAC.
Searching found two other people who had the exact same problem. (see links below)
http://www.hptuners.com/forum/showthread.php?p=247582
http://www.ls1.com/forums/showthread.php?t=110370
(link above appears to be broken)
I spent a year chasing this problem from checking for vacuum leaks, replacing the TPS and IAC. Nothing seemed to help.
Finally I tried to think what is the one common thing between myself and the other two people having this issue? We all had LS1 swaps. With that I figured I should looks into the harness. Mind you I had double checked a year ago and at the time confirmed that my IAC was wired correctly.
Last evening I decided to double check my wiring again and I found that I had switched two wires going to the IAC. The Coil B Hi was going to the Coil B lo and vice versa. I rewired the IAC and the problem has not returned. I have started the car several times now without issue.
Short version
My high idle issue was as a result of mis-wiring the IAC. Two pins were mismatched.Correcting this fixed the issue.
