rcantrellz28

Hello all, I am having a very bad problem w/my 95z 28. On Monday the car crunk up and got me to work with no problems, when I went to leave ,I crunk the car and it did fire up, but idle up and down between 900-1500 rpm and sounded crappy, I did give a little gas to see if it would help to clear it up and it revved smooth but went back to idling bad, so I turned it off , checked under hood for loose connections and no problems noticed. Tried to crank it back up and it hasnt crunk since. So I ended up getting this car towed home after having to push it down 4 floors just so a roll back could get it. Now the last 2 days I have noticed that there is no spark getting to the opti from the coil, so I bought a new coil , still didnt work, I had a ignition module and spare opti from a prior project here so I put those on as well --- still no change. I have run a fuel pressure test and I am getting fuel just no spark at all. I have tested the harness that plugs into the ignition module with a voltmeter and per what the haynes manuel says everything is ok . I have check for a bad engine grounds....... I am stumped and do not know what else to check Some body please give me somemore insight, I would greatly appreciate. No SES light . The car has only the following mods: CAI,!AIR,!EGR,MSD OPTI,MSD 6A, MSD COIL, LTs, ORY,Taylor wires,Hypercrap program.... Car is a M6

ss.slp.ls1

So it's cranking but not turning over? It seems that you've managed to eliminate your ICM, Coil, and Opti. Can you get a hold of an extra opti harness? Is the coil wire new?

rcantrellz28

Yeah the cars turning over fast like it wants to fire up , it just doesnt. The opti that I have on now is a MSD unit , it has the long harness built in to it, but when I put on my spare opti( accell) I did have to use the long harness , but nothing changed between the opti change, so I went ahead and put MSD back on.I have run spark test at plug end and at the coil and nothing at all...... I can't think of anything else aside the pcm that would be at fault, but I just really am stumped and dont no where to go now

rcantrellz28

Update: I just went to Shoebox's site and did the test on the ignition module connector and it says when testing "B" on the a/c current setting you should get a reading of between 1-4. My tests constantly came up at .1 to .2 . This is really the first time that I have had to use a voltmeter is ther any body here that has run that test ? and is .1to .2 the same as 1 or 2 ? Sorry about sounding dumb on this, but i really am getting lost.

ss.slp.ls1

I have done the test. If you are not familiar with the multimeter, make sure you are on AC setting (~V). Also make sure you are in the lowest AC setting. Do the test several times and make sure that you have a proper ground.

rcantrellz28

It is set on 200, and the reading that I am getting is .1 and .2 whenever I turn the car over, on the above mentioned site , it says that 1-4 is where it needs to be , which is where mine is (1-2) , except with me not being to experienced in reading a voltmeter, i dont no if .1 or .2 is the same as 1 or2 . According to the tests I have run the opti is telling the module to fire ( a&d terminals) and C terminal is the ground which is testing good. And testing "B" gives me .1 and .2, which means that if I am correct? all the wires in the module harness are telling the ignition module to operate, I have a spare module here and it didnt change anything when I changed it, but based off what I am reading , the module isnt functioning and I may have 2 bad modules???? by the way, thanks for your quick replies ss.slp.ls1

ss.slp.ls1

.1-.2 is not within the range of 1-4v ac. It seems that your not getting the low res signals to fire the coil. The website says that it could be your opti, opti wire harness, pcm, or wires in between.

ss.slp.ls1

You said your using an extra icm you had laying around. I say take your icm and have it tested anyway. You can never be too sure.

You said you checked the grounds on the coil. Did you just do it visually or did you use a multimeter? There should be three grounds there.

When you did the opti and spark test, you're not getting the 1-4v ac from terminal B to ground. Did you get the >10v dc from terminals A & D to ground? Did you get continuity from terminal C to ground?

rcantrellz28

Yea, I will be testing those three grounds tonight when I get home with a multimeter, all 3 are there and are in good shape( connected good/ no tears in wires). When I ran the test to A&D they both came up right over 12 , which according to Shoebox, that is ok ( in other words telling the module to fire from the opti). "C" terminal is for testing the ground up to the module and it tested what it should have. "B" is the test that I am getting .1 and .2 , not 1 or 2 ,that tells the module from the pcm to fire, which according to some of the past threads related to this one .1 and .2 is not a strong enough signal from the pcm to the module........ I dont beleive my pcm is crapped out, which means ??? Just trying to figure out what to do next.......I am positive my module is good though....

spm4520

I am going through the EXACT, EXACT same issue on my '93. I have confirmed all of the same things. I purchased a brand new coil, brand new opti, brand new harness, brand new ICM. I ran the test based on Shoebox's site. Have the proper 12 volts on A and D, and even 2 volts ac on B. I used a meter that has "auto range" finding.

I sent my PCM off to be tested so I waiting to hear back on that in the next couple of days.

As for the 3 grounds, how do you test them using the meter?

Worx

what did you find with your ecm?
where did you send it to be tested? I am having similar issues on a '94.
thanks

rcantrellz28

The PCM was ok, I needed a better tune so I sent it to Vince @ Trifecta, where he was able to rule it being the problem out........but my problem was initially a bad opti, but through the course of narrowing that problem down ,I created my own problem by being a dumb *** ,I tested the ignition module harness and when I was doing this I was sticking the prongs of the multimeter tester INTO the harness pigtail which over expanded those contacts and rendering no current or signal making contact to the module itself.So needless to say, I learned my lessonHad to buy a pig tail for the module and fired up and no probs since.