Ok here is the deal..


The computer reads and accepts a flash just fine.
Diacom doesn't show anything remarkable other than
it's running like crap (no codes).
Plug wires are fine as are the plugs.
I'm verifying the spark signal with an inductive
timing light.
The condition persisted the same after a new opti as
it did before the new opti.
The ignition controller was swapped for one known to
be working with no change.
Open or closed loop it doesn't matter.
At least two cyliinders (3&7) fire intermittently and
sometimes fire at inappropriate times. All others
appear to provide a smooth, consistent flash on the
timing light strobe.
Can't find any burnt, frayed, or damaged wires on the harness...

so where do I look next? It is defiantely a misfire and it isn't the opti..the ignition module..the coil...the plugs..the wires..the harness..and not a sensor as far as I can tell. Everything has been checked and changed to no avail. So where do I go now? could it be a bad computer and not throwing any codes? but is is talking and downloading programs??? Someone please help with some other direction I can look. Somone has bound to have had this problem.

getting desperate please help!!!!!

 

Is your programmer set on the right definition file? I had an EEB file once and didn't know it so I programmed it in as EE and it made my car act weird. I doubt that's it but it's an idea anyway.

 

not that...but appreciate the help..the file is the same..nothing introduced new into the system..installed new opti..same misfire on the same cylinders..so no that..not o2's..anyone ever had a computer failure? how does it act when one goes bad? anything wierd like this? any other things I should check??


keep them coming...

Brad

 

Everytime i've heard of someone's computer frying the car wont even start so i'm not sure that would be it. Do you have a aftermarket ignition (hi-fire, msd)?

 

no MSD or anything didn't want to add anything that would mask the problem..trying to fix it first.

 

hey someone bound to know something to look for..!!!

 

Have you checked for bad grounds especially the ones used for the PCM? How could you possibly know the bad cylinders are firing at the wrong time occasionally? I would not think that there would be a problem with the components that are common to all cylinders if you only have a problem with 2 cylinders. More than likely it would be with the components that are specific to those cylinders. You say you know the plugs, wires, opti, coil, ICM etc are not the problem. How do you know this?

I don't think an inductive timing light is the best thing to find a misfiring cylinder. A dead cylinder for sure but not misfiring. Perhaps a more reliable spark tester inline would be a better tool. What does the plugs on the cylinders in question look like?

If you are sure those cylinders are misfiring and not others, you should investigate the ignition components specific to those cylinders. Like plug wires, plugs and opti cap. Many crossfiring issues come from the distributor cap of the opti. GM's great idea of putting the contacts on the cylinder oriented side of the cap puts many contacts too close to one another and tracking in the cap is a common ocurrance.

 

please e-mail me at whitewolf_ndn@yahoo.com and we will talk in more detail...

been using a timing light..and swapping out parts...new opti..new plugs..wires..swaped everything else...

e-mail me thanks..any other options?

 

compression, fuel injectors

 

Are you absolutly sure it's an "ignition" misfire? Don't want to question your ability, but just trying to help. You can have misfires that aren't ignition related. I haven't read anywhere here where you've tested the fuel injectors for those cylinders. They can cause misfires. Also, broken valve springs can cause cylinder misfires also. It will feel like a miss. Ask me how I know this. Also, I noticed you run the bottle. Not a possibility you burned a few pistons, is it? Just throwing some stuff out there. Sounds like you have the ignition part of things covered. Hope that info helps.

Ken R. 95Z

 

Have you actually checked the plug wires with a meter?

 

When I've scanned my car in the past, my laptop can show me which misfires are occurring in which cylinders. It could help maybe in your trace of the problem. Not to insult you either, but are you sure your plug wires are matched up to the correct cylinders. It easy to mix a couple of them. And it'll make your car run horrible.

And, is the opti installed correctly? As in the notch is lined up in the dowel?

 

the wires have been checked. Ran Diacom to verify the misfiring cylinders. Wires are ran correctly. Problem was occuring before and after the new opti. I am looking for something else.

not
opti
coil
ign. module
plugs
wires
harness
ecm

checking injectors now..
have 30lb SVO's
anything else I can check?

 

I m thinking fuel or air. Have you checked commpression?..Maybe also swapping out fuel injectors.....jus' my thoughts on this......


jimmy

 

swapping injectors as we speak..?

will check compression also...