Fast idle problem---almost undriveable.

[3972plymdodge]

1983 Buick Regal with 4.1 V6. (79,000 original miles and daily driver)

Replaced the spark plugs which had almost 50,000 miles just as ordinary maintenance-----and have had check engine light on and fast idle problems since. Checked and double checked anything (vacuum lines, solenoid connections etc) I might have bumped loose. Find nothing at all. Reinstalled the old plugs just to see if any difference. Same problem.

Tried to retrieve the diagnostic codes from the test terminal by jumpering black white to black (ground)------self diagnosis doesn't seem to work at all. Get no 1,2 code with key on and no codes with motor running---just a steady check engine light. Disconnected the battery cables for a half hour just to see if the car's computer would reset somehow. Didn't help.

Did find 2 open 2 wire solenoid windings---the one for the EGR. And the one having to do with the air pump. (but not sure if either can cause a fast idle problem----they may have been burned out for years and have nothing to do with what is happening now) Electrical operated choke seems to be operating normally.

(I live in Florida so don't have to deal with extreme cold weather problems that might be a contributing factor.)

I can go to a junk yard with my multimeter and find replacement solenoids with windings that read good and try that--------but I wonder if I am even going in the right direction on this.

A guy at work mentioned the TPS might be at fault. Not sure how to check that one or even where it is exactly. There is one electrical sensor going into the carb with 3 terminals. Is that the TPS? Is that also solenoid operated? And what readings should I get between the 3 terminals?

Motor will start with a normal idle and then increase over a few minutes to a super fast idle--don't have a tach but would guess about 2000 plus rpm. A little scary to drive it that way, plus get dieseling on shut off (suppose at that fast an idle you would get dieseling).

Any way to disconnect the computer operated idle so it is an old fashioned manual type and I can at least drive the car to work until I figure out what is wrong?

Any and all help appreciated on this.

[3972plymdodge]

Actually I just did find what must be the TPS. If was a snake would have bit me.

Mounted on the drivers side of the carb and goes directly to the throttle linkage. Fed by a 4 wire electrical connector.

Suppose I just disconnect that electrical connector for now? Would it go back to strictly manual idle speed and make the car at least driveable?

I am a little afraid of screwing other things up by doing that and end up causing other even more serious problems----(will admit am a little intimidated by computer controlled anythings.)

But I do need to get back and forth to work.

[Reatta Man]

That solenoid was going to be my first place to look.

It should have an adjustable plunger that you can screw in or out ot adjust the fast idle.

Good luck.

[JohnD1956]

I'd suggest replacing the TPS first. Don't imagine that it is more than $20.00 new. Had a celebrity once with the same fast idle problem. The TPS replacement fixed it.

JD

[3972plymdodge]

TPS replacement sounds like a good place to start.

It is driveable now that I turned the throttle adjustment down one full turn. But it does act strangely. Smooth as silk when cold, misses quite a bit when warmed up, at least at idle---but never dies--, fine at higher speeds.

Choke crapped out on me for some reason just recently. Have it held wide open with a piece of garden hose stuck in there. And I don't seem to really need a choke in Floriduh for starting---just pump the gas a couple times and let it warm up for a minute before taking off.

[JohnD1956]

Good plan. You've really had quite a few issues with that car, havn't you?