95 850T runaway RPMs when started

greg850r · Post by **greg850r** » 07 May 2026, 14:50

Has anyone ever had one run at 4000 rpm when started for no apparent reason? I reached in and manually held the throttle body shut to no avail. The only thing I could do was shut the key off at that point. I am reluctant to start it again because I don't think the turbo bearings will survive another 4000 RPM ignition kill.

Post by **erikv11** » 07 May 2026, 15:37

I think this could point to there IAC being stuck open? Or maybe the TPS is ruined and the ECU thinks the throttle is still open.

Easy to clean the IAC unless the hoses on it have turned to stone. Remove, fill with carb cleaner, shake to rotate the gate inside, dump out the carbon. Repeat.

TPS I always troubleshoot by swapping in another one, it's just an easy way to do it.

aeg · Post by **aeg** » 07 May 2026, 17:01

IACV stuck wide open, throttle vane bent, intake manifold came loose?

I don't think it could be TPS, it's not likely to get to 4000 RPM without tons of air coming in the intake.

Post by **matthew1** » 07 May 2026, 20:25

IAC, vac leak, etc. Something with air/fuel mix.

greg850r · Post by **greg850r** » 09 May 2026, 12:52

Thanks guys. I also doubt the IAC flows enough for this. Will swap in a TPS and look hard for an intake leak somewhere. It's time for PCV service on this one anyway so if I can't find anything I'll use a different intake when I R&R it.