My 87 S4 auto has recently developed a high (1,100) idle condition after the engine is warm. After revving the motor the idle drops to to maybe 800 (indicated) but then "snaps back" to 1,100 where it idles steadily. I've searched through previous RL posts to see if anyone has written about this but didn't find much. The way that it crisply rises back up leads me to think that it's not vacuum related. I can hear the idle switch click but haven't checked with a multimeter at the LH/EZK connectors since a routine check prior to the high idling. I know that I need to get in there and test things out to properly troubleshoot this but am wondering if anyone could point me in the right direction if they've experienced this before. The PO did an intake refresh a few years ago but I think that he wasn't extremely thorough so I anticipate doing it again, perhaps next winter. Could this be a symptom of a tired MAF?

Thanks for any insight to this. I'm super busy at work and home these days and garage time is at a premium so it would be nice to have a couple of ideas of what to look for.

 

the usual fail point is the cable from the foot pedal to the throttle quadrant, so disconnect this cable from the throttle quadrant, and with a helper see how much effort it takes to return the cable to the idle setting.
you can slide the housing out of the firewall to inspect it the cable you may find it starting the unravel.
if this cable is good,
then check the operation of the throttle cable to the TPS,
it may be a turn too tight ,
do the checks with the engine hot,
also inspect the cable run maybe you have a fuel line, vacuum line or wire harness rubbing on the this cable,
this will require air cleaner removal