Random rough idle..no clue?

[mineroller]

My car's been doing rough idle randomly since last fall..
It happened some time after (maybe like a few weeks) I put a bottle of STP fuel injector cleaner I got from someone ..at the time i think i had about half a tank full of gas and i poured the whole bottle in.

Now the car randomly, though not very often, idles very rough.
RPM guages dance like crazy in 500-800rpm area and it almost stalls..it acts like something is clogged or it's not sipping gas correctly. But..it only does it sometimes..and it goes away after a while..
it does it even when the engine is fully warmed or after driving normally for a while. It suddenly comes then dissappears..

what would be a problem? since the car runs normally with very quite idling @650rpm most of the time, i have no clue what the heck would cause it..

I have no mods except an MSP exhaust, which i installed only a week ago..so that's not any issue.
I had rough idle just couple days ago on road..

Anyone have an idea?

[zmanpro63]

My car's been doing rough idle randomly since last fall..
It happened some time after (maybe like a few weeks) I put a bottle of STP fuel injector cleaner I got from someone ..at the time i think i had about half a tank full of gas and i poured the whole bottle in.

Now the car randomly, though not very often, idles very rough.
RPM guages dance like crazy in 500-800rpm area and it almost stalls..it acts like something is clogged or it's not sipping gas correctly. But..it only does it sometimes..and it goes away after a while..
it does it even when the engine is fully warmed or after driving normally for a while. It suddenly comes then dissappears..

what would be a problem? since the car runs normally with very quite idling @650rpm most of the time, i have no clue what the heck would cause it..

I have no mods except an MSP exhaust, which i installed only a week ago..so that's not any issue.
I had rough idle just couple days ago on road..

Anyone have an idea?


Do a search on rough idle, there is a lot of info out there. Seems to be a fairly common problem with our cars. I have a 99 with the 1.8 litre and I have been dealing with the rough idle since last year as well. Seems like some people fix the problem with EGR valve service or grounding kits, sometimes just new plugs. Ive tried all of those things and more and I still have the rough idle, so.........good luck, I post every time I try something else. Thanks Nik

[Shane5425]

zman, put your stock intake back on, i bet your rough idle will be gone.. i found that out with my car. as for mineroller, try doing a tune up, then clean or replace the egr selinoid

[zmanpro63]

zman, put your stock intake back on, i bet your rough idle will be gone.. i found that out with my car. as for mineroller, try doing a tune up, then clean or replace the egr selinoid

Thanks, if I get totally bummed I may do that, but today I noticed a couple of things first the idle seems to be better. Now its alot warmer here today in the 40s and its dry, my car has never liked the cold here so that may be a factor. Second I am now on my third tank of premium, I know people say our cars work best on 87 but my car just seems to prefer premium, maybe its the extended reach plugs or some other mod who knows. Also I know because it gets cold here that the gas we use has different additives in the winter than the summer, so maybe there is something in the gas my car didnt like, also I let my car sit an idle for 10 or so minutes before I walked into work, one thing I noticed is as the car reached its hottets the idle was rock steady no hesitation whatsoever, when I drive it the temp is lower and the car has a rough idle, Im wondering if there is something between engine temp and idle? Hmmmmm just wondering out loud, anyway after Friday hopefully I'll get rid of my cel once and for all and I can drive awhile without it, car should like that. I'll post any findings thanks Nik

[wannabe]

Thanks, if I get totally bummed I may do that, but today I noticed a couple of things first the idle seems to be better. Now its alot warmer here today in the 40s and its dry, my car has never liked the cold here so that may be a factor. Second I am now on my third tank of premium, I know people say our cars work best on 87 but my car just seems to prefer premium, maybe its the extended reach plugs or some other mod who knows. Also I know because it gets cold here that the gas we use has different additives in the winter than the summer, so maybe there is something in the gas my car didnt like, also I let my car sit an idle for 10 or so minutes before I walked into work, one thing I noticed is as the car reached its hottets the idle was rock steady no hesitation whatsoever, when I drive it the temp is lower and the car has a rough idle, Im wondering if there is something between engine temp and idle? Hmmmmm just wondering out loud, anyway after Friday hopefully I'll get rid of my cel once and for all and I can drive awhile without it, car should like that. I'll post any findings thanks Nik

try the good ole reset the ecu. i had this problem pretty badly for a while, but i did a oil change, new pcv valve, new spark plugs, fuel injector cleaner, and reset the ecu, it got better..now it only does it occasionally.

yeah ohio weather sucks....but wait 15 minutes, it'll change.

[zmanpro63]

LOL yeah you always know people from Ohio, frickin weather, who would have thunk we have more cloudy days than Seattle. Oh well 52 right now and 5 inches of snow for tonight go figure, Im gonna go hide in a hole with a bottle see ya