s52 idle surges
 

hey all, my s52 swap idle likes to surge up and down when sitting idle, also when coming to a stop or neutral.. not all the time, but would like to have a smooth idle.. is it icv?

My M52 sometimes does this also, although only when coming to a stop in neutral/clutch in. I'd love to hear if you find a solution for this. It seems to happen more when it is cold out (< 40 f)

haha hopefully i figure it out, i think it may be electrical.. it happens alot more when its cold out aswell, but also when i have my A/C running... use to happen with my m42 aswell.... what year is your car? mine is a 95 obd1 swap

Start with the IAC, clean it test it. Then check for any vacuum leaks.

IAC??? is this the Idle Control Valve (ICV?)

Idle Air Controller or Idle Control Valve. Different terminology

Mine is a 98 with an M52 out of a 97

Yes, both of those cars should have IAC/ICV.

Check vacuum leaks; I had a bungled o-ring on a sensor on the underside of the intake manifold. I built a smoke machine using a GM diesel glow plug, a 1-qt. paint can and pharmacy glycerine. Hooked it up to the air intake boot and voila -- I easily found the leak and solved the hunting idle.


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Ditto on the air leak, either the boot between the MAF and throttle or vacuum line.
My S50 has similar idle surge during the transition from cold to warm, when the temp pm gage is just out of the blue. It seems a little lean then, but it's fine when fully warmed up.