Okay. I've read probably a hundred threads and I've found some issues exactly like mine. But as it turns out the thread ended without a cured post on each one. So I'm forced to ask this question for the millionth time.

I'm having an idle issue. It doesn't seem to be an issue until it goes into closed loop. It's not like a constant miss like from a fouled plug or bad wire. it's hard to describe but it's like a hicup and random, meaning not happening in a given sequence.

It'll go prrrrrrrrrrrrrrrrrrrrrrr hicup prrrrrrrrrrrrrrrrrrrrrrrrrrr hicup hicup prrrrrrrrrrrrrrrrrrrrrrrrrr hicup prrrrr hicup prrr.

Here's the history of what I've replaced because of other issues and also because I'm trying to replace common problem issues, on a 20 year old car, that are prone to go bad. And so that I know more of the history of the car.

New fuel pump, filter, injectors (Bosch III from Jon) FPR. New IAC, plugs, cap and rotor. New intake gasket and valve cover gaskets, and waterpump and serp belt, catback. along with some other interior upgrades.

I didn't notice it doing this before I replaced the plugs, cap and rotor but it may have been, if it was it sure wasn't as bad.

I put in AC delco rapid fire plugs and I did take them back out and rechecked the gap and inspected them and they seemed fine.

I've read things like EGR, O2 sensor, injectors, IAC, vacuum leaks and you name it. But so far I haven't read anything that said, hey that's what it was.

Just looking for ideas. I don't mind replacing a couple things like O2 sensor or EGR and things like that, as I said I'm trying to replace most of those items over time anyway so I don't feel I'm throwing parts at a problem. But I would like to try and pinpoint the issue as closely as possible.

Any ideas will be appreciated. Sorry for the long post.

I will also add that it seems to run fine other than when in idle from what I can tell. And I did recheck the Fuel pressure and it was fine. 40 to 42 and dropped to about 32 to 36 after a few minutes and stayed there. Also the RPM's seem to hold steady without any jumping during the hicup.

 

Since you say the problem may have started when you changed the plugs, cap, and rotor that would be where I would start looking..Are you using the same brand, heat range, plugs that were in the engine before the problem started?? Also just because something is new doesn't mean its any good, I can't count the number of bad, (new) parts I have put on my cars in the past..If your car is close to stock I would just use the original / stock AC Delco spark plugs that came in the car from the factory, these have worked fine for many years and are much cheaper and sometimes work better then the exotic stuff..If you saved the old plugs, cap, and rotor I would reinstall them to see if the problem goes away, this would answer if it was those parts that caused the problem......Good Luck...WW

 

You know I'm one of those guys that saves everything I take off a car, just in case. But this time I threw them all away for some reason.

They were NGk plugs and actually seemed fine. They were carbon fouled previously from my fuel issue but when I took them out to replace them the carbon had bured off, but I replaced them anyway.


I kinda agree that my issue may be what I put on and I do plan to start there. But I've had dual issues before and I want to make sure I don't get brainlocked and focused in just one area and drive myself bonkers.

Thanks for your input I appreciate it!

 

I've gone down the same road with my '86. I'll change one thing, it'll be fine for a while , then the stumble returns. Sometimes with a code or two, lately none. I'm beginning to think my wiring harness is bad, one day it runs fine and out of the blue, it stumbles. It's only drivin at my leisure,(weekends) so I just motor on 'till it settles down. Most posts don't have a followup, so I don't know if anyone has really fixed it or not. Mine's similar to water in the gas....

 

If you find something definite, I would appreciate it. I have several hundred hours in reading posts and trying things on my 89. I think now it must be something in the heads so I am going to have them removed and checked this winter. Have tried everything else...Multiple plugs, wires, distributor, injectors, fuel pump, have had the valve covers removed and rockers and springs checked. (Would love to find something BROKEN!)

My email if you find something for sure is wa4ky@insightbb.com I will dance at your next wedding if you come up with the answer!

Gary / Louisville

 

I will work on this until I get it fixed and when I do I will report what I find. If you never find a follow up I haven't fixed it. That's a pet peeve of mine. Following up on these help threads.

 

I'm leaning to something electrical for some reason. As it seems it's more prevalent when the AC is on, but that could just be because it's under load and more pronounced.

I checked the cap and rotor last night and all seemed fine. I put new injectors in but I'm going to ohm them as well because I don't think the thing cold starts like it should.

I knew I would spend time fiddling with this thing when I got it but it's starting to become a nuisance. After all I've done and everytime I do something, something else pops up. It seems to run fine but things like this drive me bonkers.