Wandering idle

[135sohc]

2.2 single point injection/tbi
246,000 miles
A523 transmission

My DD Shadow has had idle issues for awhile now and in the recent months its only gotten worse. Does not have typical cracked vac line high idle but rather its got an idle speed thats lower than it should be :confused:. idle speed should be 1000rpm +/- 100 rpm according to the fsm. It has chosen 750 rpm for the most part. Sometimes it dips as low as 500 (and gets really rough) and sometimes like tonight it was wandering between 750-1000rpm every few seconds.

No codes. tps is original, idle speed motor was replaced a few years ago. Cleaned out the throttle body assembly recently but made no difference.

Ideas ? I read the KC article about resetting the base idle and using the screw to dial it in but that doesnt seem to be the entire problem here. Like something is corrupting the signal and the IAS cant do its function properly.

[RoadWarrior222]

I've got something a bit similar happening with my '88 3.0 at the moment, hasn't quite got troublesome enough for me to tear into it. I was thinking maybe the IAS plunger thing got sticky and was gonna try cleaning it out.

[shelbymonster]

on my 2.2t when i had a big exaust leak before the o2 sensor and idle was jumping a lot ,fixed that and problem went away , im not sure if tbi has a o2 sensor

[jory]

My 3.0 did it BAD when I had the automatic computer in it. More recently (like yesterday) My Daytona would do it, but a new O2 sensor fixed that. I know a couple people whose cars do it too and they aren't even turbo mopars.

[135sohc]

I have a growing suspicion that the HG is seeping coolant again :( and has poisoned the oxygen sensor...

Will know tonight after work.

[RoadWarrior222]

I have a growing suspicion that the HG is seeping coolant again :( and has poisoned the oxygen sensor...

That would be ungood. Though coolant was supposed to be silicate free these days.