High idle

Well its that time of year.Well my jeep has never seen any thing lower then 30 deg.This is my problem.When I go to start it up in the mourning,it starts and runs fine(I did run seafoam in it so im wondering)It sits for about 10 min or so,so I know its warm enough to drive.Now this is were its tricky,I guess,It will get up to ideling to about 1,500 rpms and doesnt come back down till after I drive it a few miles or so,and some times wont come down at all.Now mentioning the seafoam couldcould it have made it run like it suppose to now? Maybe the idle screw was out to far from, the get go,maybe the different gas?Remember its never seen really cold befoe.Its been in Texas,VAgas,and Florida and now Indiana.I just did a tune up on it about 6 months ago,and drive it fro FL to IN.Any suggestions of what it might be??Thanks in Advance
Hog

A lot of junk builds up around the IAC stopper and seat. Especially in the Renix. When the gunk gets softer from heat the IAC will often function OK or at least better. And/or a weak battery, will cause the IAC to stick sometimes, it just doesn't have the juice to move the plunger/stopper through the gunk.
Behind the plunger/stopper there is actually a threaded rod that a tiny motor moves in and out. The rod is greased, the grease gets thick, a drop of oil (I use synthetic) behind the plunger often helps. Just a drop beside the plunger so gravity takes it behind the plunger. Don't try to pull the plunger out or leave it pluged in and turn the key on. You'll likely strip the teeth in the motor, on the rod or launch it cross the driveway (there is a spring in there).
Clean all of the buildup from the plunger and the seat. I use a penetraing oil to clean everything up, solvents can cause problems. Spraying a little penetrating oil into the IAC orifice, every so often, seems to keep mine fucntioning properly, I do it at least twice a year or whenever it acts up. I spray the oil into the orifice while the motor is running and work the throttle a little, so the IAC plunger moves around some.

Clean the throttle body, deal with the IAC as per 8Mud's post, and if you still have an erratic/inconsistent high idle then change the TPS. The TPS must be calibrated on Renix 4.0s. My 1990 is on its third TPS.

Hey, another Hoosier.....yay.

Im new to all the 4.0 things could you help out a little bit??

Remove the idle air controller and the throttle position sensor. Clean both with brake cleaner, clean the plugs too. Then spray some WD40 on the spring inside of the Idle Air Controller (below the tip) and maybe a little squirt into the throttle position sensor. Put both back in their respecting slots, reconnect plugs, and tell us how it works.

If you clean the TPS with carb cleaner or even water, you can go ahead and buy an new one. They tend to leak and do not tolerate cleaning very well. Simply washing an engine and hitting the TPS, routinely causes failures.

Blaine B. said:

Remove the idle air controller and the throttle position sensor. Clean both with brake cleaner, clean the plugs too. Then spray some WD40 on the spring inside of the Idle Air Controller (below the tip) and maybe a little squirt into the throttle position sensor. Put both back in their respecting slots, reconnect plugs, and tell us how it works.

Click to expand...

Well I just did the tune up on it ....unless the guy who had it before me never took care of it,and me changing all these things actually may have done something good for a change.I havent checked the plugs since Ive put them in.Oh by the way Blain(seeings how your up here to) what oil(weight and brand) and oil filter(brand) do you guys use up here,I was in Florida So I ran thick year round,so Im new to haveing a heep in cold weather.

I use 5w30 or 5w40 Valvoline max-life for high mileage, and I'm using a Delco oil filter and a Wix fuel filter.