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Discussion Starter #1
the object to this thread is to make a some what of a check list of everything that can / has caused a idle issues/ surge and a mis fire...

i dont need the entire story, just what fixed the issue

i have noticed latly there is a asssss load of threads about mis/rough idle. 80% of the time people jump to opti's. I personally dont think the opti is the root of all problems, ya its a pita but a well taken care of opti will last years.

please post something you have fixed,or have had fixed....not something you have read and you think can cause a mis or rough idle.

IF you post something general like a vacuume line, please explain what line it was...


i will start.

spark plugs(crossed wire and or bad wires)
bad sparks & incorrectly gapped sparks (0.50 fyi)
ICM
Vaccuum (the line that comes from the front of the TB to the side of the head)
opti
opti harness
fuel pump
fuel filter
coil
 

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Here's my reply in a similar vein from back in Dec.;

oh boy would YOU be getting reamed for not Searching if the server hadn't wiped out everything.... cwm1

There's about a billion documented causes of off-idle stumble;
intake leak
IAC
MAP
Vapor Can
plugs
wires
vac hoses
water pump - yes, it drips on the opti
wet/humid opti

that'll get you started.

Added:
EGR
Of course several overlaps with your list -Wolf, but I notice no mention yet here of intake manifold leaks. That's so obvious (and gotta be real common on a 15 year old iron motor) that I guess I always overlook it.
 

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In my case the previous owner had a mechanic tune up the car, new plugs and wires. ran rough and missed on one cylinder. One plug on the passenger side was loose, had oil on the threads and would not make a good ground. New plugs took care of it.
 

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My experience:
1. Ignition coil was shorting internally, making a tic noise every time it fired that was tied to engine RPM. The car ran noticeably better and started quicker with a new coil.
2. Fuel injectors can and do partially fail. My wagon had run hot for awhile and was poorly maintained. I sent the injectors to Witchhunter performance and they found 2 or 3 injectors that flowed at around 60% of capacity with an awful spray pattern. One was also not opening in time so we had to junk that one. It costs around $17 apiece to have an injector tested and cleaned. Cheaper than a tuneup.
3. The #7 spark plug wire will short on the frame or brakelines when wet if you don't run it in the factory loom, or build a plastic/rubber insulated holder assembly. If you tie it to the frame or brakelines, leave enough slack for the movement of the motor relative to those components, otherwise the motor will pull that wire off when you rev it.
 

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for those that do not know, the spark plug wires ALL have to click twice into the opti or they are not seated properly:D
 

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I had a fouled O2 sensor that caused a closed-loop multi-cylinder misfire on the corresponding side. Unplugging the O2 sensor and driving it verified it, as it ran on all 8 cylinders that way.

Also, in cold weather if I didn't wait for it to warm up, It would run great until you could first feel a little heat coming out of the vents, from that point on it ran like crap.
 

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there has to be alot more....who has fixed their idle issue post up
ok on my 95 i had a misfire on the passenger side only.... pulled every plug put in different plugs and tried 2 new sets of wires to only find out my opti was fried..... MY 95 THREW NO CODES AND WAS MISFIRING FOR AROUND 2 WEEKS until i got brave and switched the optis myself..... all this was caused by a faulty opti vent harness i have since made a home made one and it flows great!!!! screw paying $60
 

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ok on my 95 i had a misfire on the passenger side only.... pulled every plug put in different plugs and tried 2 new sets of wires to only find out my opti was fried..... MY 95 THREW NO CODES AND WAS MISFIRING FOR AROUND 2 WEEKS until i got brave and switched the optis myself..... all this was caused by a faulty opti vent harness i have since made a home made one and it flows great!!!! screw paying $60
Would you mind sharing your experience? I mean the home-made vent harness. The vacuum at mine is so weak that I can visualize it only with a WET piece of paper towel. I know it's supposed to be weak, but not sure it is supposed to be THAT weak. Need to shot a video clip probably to show here.
 

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Discussion Starter #13
Would you mind sharing your experience? I mean the home-made vent harness. The vacuum at mine is so weak that I can visualize it only with a WET piece of paper towel. I know it's supposed to be weak, but not sure it is supposed to be THAT weak. Need to shot a video clip probably to show here.
the wya i have tested it, car on and a paper can be held in place by the vaccum = good working opti vent harness
 

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In my case, I believe it to have been caused by loose manifold bolts on DS misleading the PCM into thinking that bank was too lean, resulting in a too-rich situation. Tightening the bolts **hopefully** fixed this gremlin.
 

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ok on my 95 i had a misfire on the passenger side only.... pulled every plug put in different plugs and tried 2 new sets of wires to only find out my opti was fried..... MY 95 THREW NO CODES AND WAS MISFIRING FOR AROUND 2 WEEKS until i got brave and switched the optis myself..... all this was caused by a faulty opti vent harness i have since made a home made one and it flows great!!!! screw paying $60

well due tell im dealing with a hesitation when i first start the car but when it warms up its fine,what did you use for a vent
 

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my 3 cents

I have had rough idle and sudden failure during acceleration several times, here were the problems in the order they occured

OptiSpark - 135k on it though and thats pretty good
MAF Sensor, for whatever reason it went bad, I never understand how one wire goes bad (so, I did some testing when I got the new one and Cleaned the old one, used a hobby razor knife for model cars and a magnifying glass and very lightly rubbed all contaminents off of the wire, I was surprised how easy the buildup came off, worked perfect, like new, because I compared the two, and just kept the new in, still have it 2 years later in box)

SPRK PLUGS, NEVER will I use Autolite again. Even the most expensive Autolite doesnt hold up to a Copper Champion. So I use Delcos

The last thing was intake and exhaust manifold bolts being loose. (You would have thought this would have been the first thing to notice, but in a matter of a few weeks they went from no problem to chugging)
 
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