i have a 96 Z-28 with a freshly rebuilt engine. when i had it rebuilt i put a new opti, plugs,wires,and alot of sensors. i also put a 160 thermostat.

when i drive it, it has power and everyhting just it backfire and sometimes stumbles and almost stalls. i have checked the coil at autozone and it was a lil worn out but i dont think its enough to cause a misfire (5.84 while a new is 6.something low) i have also checked EGR valve to make sure its not sticking open causing a vaccum leak. double checked all connections and had MAF sensor cleaned(it had alot of dirt in it from sitting in a box.)

the only code i am getting is the random misfire code. and i cant seem to find out why. any help at all is greatly appriciated.

 

Have you looked at the ignition control module?

 

I have not. i was looking for a way to test it but i still have not thought of anyother way then trying it with a known good module. i forgot to post in my last one that i have also cleaned out the MAP, IAC, IAT sensors also. i have ran a bottle of seafoam through the car also.

do you know of anyway to test the ICM without buying or borrowing a new unit?

 

sorry, i have some more info that i keep leaving out.
-the SES light flashes, then solid, then flashes. just off and on pretty randomly.

- if i clear the codes, start the car, wait till the code pops up(sometimes right on fire up and sometimes can take up to 30 secs) and scan it the code will either come us as cylinder 3 misfire or cylinder 6 misfire(usually 3 tho). then if i turn it off and start it up again it will be random. im thinking maybe only cylinder 3 and 6 are misfiring and its just calling it random since its the cheap actron reader from autozone.

.....help......please......

 

The scanner is OK. It only reports what the PCM sees. You may want to take a good look at the plugs and wires for cylinders 3 & 6, sometimes the wires will touch the exhaust and the insulation burns up and the spark can jump to ground.The blinking MIL lite is a sign of misfire. Also check the plugs for fouling, tip color , and gap. Too big of a gap will force the spark to jump through the wire insulation. The 3 & 6 plugs fire are next to each other in the firing order, so there is a possibility of cross fire if the wires are not run according to factory layout,or if they are run touching each other, also the distributor cap could have carbon tracking between cylinders 3 & 6.

 

alright im gonna go ahead and look at the wires today. the spark plugs come pre-gapped(bosch double platinum) so im pretty sure the gaps will be within tolerance.

also the distibutor is brand new so im pretty sure that it wont have and tracking or anyhting.

do you know of anyother possibilties? or of a surefire way to check the ICM without buying a new one and throwing it on there?

thank you so much for the help!

 

Just my .02 cents worth, but you should ALWAYS check the gap of your spark plugs before you stick them in. Thay ALL say they are pregapped but I have found that they are usually not gapped correctly. Plus you gotta think about the fact that they are bouncing back and forth in those little boxes during shipment which means they are all going to be a tiny bit off.

 

Just a word of advice, I really had some bad results with Bosch plugs and wires on several different cars. Seems that some of the plugs just don't work right out of the box. Put in some factory stock AC Delco. They are expesive but work properly. The wires started acting up within a year, where the factory ones were good for about seven.

 

sorry i havent looked at my car or this site for awhile.

anyways, i have replaced the coil in the car since the resistance on it was off by a little bit. it didnt change anything when i started it.

i let it sit for maybe two days and now it wont start at all. it will crank just fine but it does not even sound like its trying to fire up at all. i have read a few things about the crankshaft position sensor needing to be relearned(since i replaced it with the rebuild) but im not sure if that is my problem since i have not gotten the code.

tomarrow i will be taking off all the plugs/wires and checking them over to make sure they are not the problem.

anyother ideas so that i can get it all done when i look at it tomarrow?

i think i am also going to have to replace the ICM becasue the casing got a lil cracked when i was knocking the rivits out of the coil =/

thanks in advance for any possible help.

 

well i replaced the ICM and got it to start again. still has the misfire. but at least i can start it.

i checked all plugs and wires and they checked out good.

next i i checked spark, with a extra plug on each cylinder wire. when i got to cylinder 3 my friend held the throttle at about 2000RPMs.
when ever he gave it gas the spark would cut out and not fire at all, but the engine as a whole would run smoother

still a misfire but its not making the engine shake and jump around everywhere.
chevy dealer told me it might be a bad optispark. any opinions on this at all?

i only checked spark on cylinder 1 and 3. 1 is fine and has a good spark all the time. 3 has nothing under accel.
swapped wires with no diff. results.

any help is needed