official rough idle/surge/misfire

[thebigbadWOLF]

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

[Mean SS]

power wire to coil "black coil connector" on 94-95 coil, the wire was corroded and frayed internally no change in how it ran with wiggle test

[Rocko350]

Egr valve. Car will even present with running a little hotter than normal, stalling while coming to a stop, and on cammed cars can cause a part throttle surged when not tuned properly.

Chris

[96 Black]

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

Originally Posted by 96 Black

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

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.

[95BRMW]

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.

[sherlock9c1]

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.

[POPIMPIN CUSTOMS I.N.C.]

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

[thebigbadWOLF]

ttt ..

[DiGGM95]

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.

[thebigbadWOLF]

there has to be alot more....who has fixed their idle issue post up