High Idle after manual swap

[hayden_duffy5]

Hey Guys,

I recently manual swapped my 88 535is from automatic in Late October of 2022 with a G265/6. After the swap my idle is much higher than before and I can not seem to figure it out. When the car was an automatic the idle was never super steady but stayed anywhere around 700-900rpm.
After the swap the car felt and drove amazing except for the fact that the idle (warm and cold) would consistently sit at 1200-1300rpm. There have been times when it would drop back to its normal idle speed but usually goes back up after driving then back to neutral (such as going from one redlight to another). At first I thought maybe it could be the ICV so I took it out and cleaned and sprayed with wd40. After that no change. So now I’m thinking it maybe a vacuum leak or something to do with the computer.

If any of you have any idea what may be causing the high idle or have experienced this yourself after a manual swap, any help and input is appreciated.

Thanks

[kojo96]

Automatic and manual have different TPS sensors, double check it'sworking correctly, that might be your problem. Also check you ICV.

[Mike W.]

Too much air (vacuum leak) or the throttle is partly open. More likely the latter. The throttle cable should be slightly slack, have just a little play in it and not be preloading the throttle at all. The TPS should show closed at idle too.

[Shawn D.]

Automatic and manual have different TPS sensors, double check it'sworking correctly, that might be your problem.

While they are different, the difference is related to WOT signaling, not idle position. The idle position switch function could indeed be the issue.

[Shawn D.]

BTW, OP, did you do anything to replace the WOT function? On automatics, it's provided via the transmission control unit, so if you do the swap and don't change to a manual engine harness and manual TPS, you need to wire the WOT signal to see ground at full throttle. I used the kickdown switch and wired it to ECU pin #3.