I posted awhile ago about my 86 4 cylinder refusing to idle, it is constantly searching for the right fuel mixture it seems...surging back and forth. smells like catalytic converter at an idle. The car runs fine at higher rpms, but the idle jumps all over the place. We have searched for vaccum leaks, replaced all rubber vaccum lines, it has a new intake to throttle body gasket, the throttle body is fully rebuilt after being soaked in carb clean, new iac sensor, new 02 sensor, new fuel pump 3 thousand miles ago, and new fuel filter. Everything but the fuel pump has been done SINCE the idling problems, but the car ran perfect for quite awhile after the new pump. i have borrowed a map sensor off a friends car to test that, and same thing. Any ideas? anyone have the same problem at any point? im running out of ideas....no service engine light on or anything. I dont wanna have to take this car to a garage, I like to do these things on my own, but Im currently stumped what to try next. Im a college student on a budget and this car is my gas saver, so i cant just go throwing every new sensor and part till i find the right one. any thoughts? thanks

What is the idle range when cold and when at operating temp?

J.

Check all ground connections. Loosen and re-tighten all nuts/bolts where ground straps/wires are attached to the engine or car.

New ecm.... try to swap one out, could just be a bad computer... Or its possible your fuel pump is partially clogged or under powered, if underpowered do as previously stated, clean all connections throughout..

good luck

You said you installed a new IAC sensor. Did you mean IAC valve? If not, try cleaning it with carb cleaner. There are threads about doing this.

yes, the iac valve. just replaced it. had already tried cleaning the old one with carb clean. The tach is off in rpms but i would say the idle surge is between 600 and 1500 rpms back and forth. I hate to buy a computer and find thats not the problem,as i said money is a concern, i have put a good amount in the car without going crazy to this point and its more of a money SAVER to this point, hate to change that.ill try cleaning up the ground straps and such but the car is very clean rust and corrosion wise, i wouldnt think it was an issue, but i will go over them. the fuel pump sounds normal, like the old one (the rubber connector that goes from the sending unit to the pump had split and i only replaced pump because i was already in there). i was thinking maybe a fuel pressure issue, however that doesnt make sense to me if the car runs normal after certain rpms. thanks for the replies ill go through and check those ideas

You may want to take it to a shop and have the diagnosis it.... that may be cheaper in the long run. You don't have to have them fix it, just tell you what is the problem. Just a thought.

J.

Check power, ie alt wire and battery mains, and grounds.
Check main disconnect under C500.
Check Alt and alt mounting

Car idle funny with power or grounds are bad.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

how long ago and where did you buy your TPS
autozone has the biggest P.O.S. electronics in the world
brand spanking new tps went out in two weeks. they wouldnt replace it because they said i abused it by supplying excess of
13 volts to it.
napa or fierostore for all fiero parts. carquest is ok in most situations too.

all parts are napa parts that i have done.

hey, just wanted to thank everyone for all the suggestions, and let you all know what i found with it. After all this time i feel stupid for not checking this earlier, but oh well live and learn, all the other things replaced will just be stuff i shouldnt have to think about for awhile now.Tore into it, and found a SIMPLE fix for it....EGR valve. It was either stuck or the gasket was leaking. replaced the gasket, worked the valve back and forth, and the car runs good as new! thanks again, and hope maybe this helps someone else along the line.


Matt