Engine is an M50B25, working fine up until the last week or so.
At idle the engine surges between around 1500rpm and almost nothing every couple of seconds. Eventually the engine will choke out. Works 100% fine in use, only the idle is affected.
What I've tried:
Disconnect the MAF --> doesn't fix the idle.
Adjust the throttle so it's open a little --> This fixes the idle as a work-around, and it's how I'm running it right now.
I've tried a different TPS and a different ICV --> no different
ICV buzzes ok on startup.
It seems to me the problem is ICV control, the ICV does seem to be working but the ECU seems unable to make the correct adjustments for some reason.
I'd welcome suggestions on possible causes. Again, the engine runs fine in use (throttle open) and idles fine with the throttle open a crack.
What sensors are involved in the idle control??
Inlet manifold temp sensor?
Engine temp sensor?
Thanks in advance for any advice.
