I've been having a lot of problems with my 94 LT1 missing. Replaced coil, ICM, Coil wire, computer..... So I finally looked under the hood at night last night and the coil and coil wire are arching all over the place. It's wierd there's just sparks goin everywhere. I'm at the end of my rope and I don't know what else to do. Had it scanned and it said the ICM was bad after I'd already replaced it. So a tech told me it was the computer. Replaced the computer and thats when I noticed the coil and wire arching all over. Any ideas?
-
-
yep. Time for new plug wires. you might look into ditching the metal boot covers too. Get taylor firesleeves instead. The spark energy is taking a path of least resistance......
-
I agree, and I would have done this long before just assuming the PCM was bad.Originally posted by Joe 1320Comment
-
HaHa,didn't assume anything. A tech told me that was what code meant. Anyway, New wires huh? Sounds reasonable. I'll try.Comment
-
There are a bunch of misleading codes that could lead one to believe(even a "tech") that there was a problem with a circuit within the PCM. Especially with primary ignition codes. It is farely rare that the PCM's themselves have problems.Originally posted by tuhy979
Did this "tech" perform and kind of isolated diagnostic tests on the PCM? Did this "tech" measure and record voltage, voltage drops, and resistance throughout various pinouts and circuits? Were there any codes that were PCM specific? Did this "tech" perform any type of "logic tree" tests on the coil and ICM itself? etc. etc. There are so many tests to perform before you even think about just replacing the entire PCM.
Faulty or old plugs and wires can posses higher than normal resistance and create a greater load on the coil and ICM, thus causing the coil and/or ICM to look for closer path's of less resistance. This could be the arcing you see.Comment
-
Wow, like, you're really smart! No this "tech" didn't do any diagnostic tests or any of that other high "tech" stuff you said. I guess he wasn't that smart. Anyway, new plug wires worked. Thank you for the help. Now at the risk of you tryin to make feel like an idiot, I have another question. Since I put the new PCM in it won't shift back down out of third gear. After start up I have all three gears untill it gets to third, then it won't shift back down. Can't shift manually either. Had it scanned and the computr isn't telling shift solenoids to shift. When it gets to third both solenoids are getting an "off" signal. You think maybe programmed wrong? If so is it possible to change shift points? Just a reminder it is a 94 Z28 with an auto.Comment
-
Don't you still have your old PCM?Originally posted by tuhy979Comment
-
No I had to bring it in for a core. I wish Ihadn't now And I should have held on to it but they already shipped it off. I tried to find one in a junk yard around here but
of them have one. Do you think I should I should just bite it and take it in to the dealer? Don't want to cause it's soooo expensive but maybe I should.
Comment
-
It sounds as if your 4L60E is going into 'Limp Mode'. This is likely because you have installed the wrong PCM, but there is a slim chance that it is actually your trans.
The PCM monitors all of the transmission sensors and indicators very closely and it expects a certain voltage window at various pre-set trans temp tables. If this voltage is outside of this expected range, the 4L60E can be placed into 'Limp Mode' to protect the trans from any further damage. The PCM instantly commands a very high line pressure ignoring the normal continuously varying line pressure commands, turn off the shift solenoids, and defaults to a single gear; usually 2nd or 3rd. The reason for this is to protect the bands and clutches should there be a 'real' problem.
I've seen this happen before when people have swapped PCM's, and it turned out to be the wrong PCM for the car. There are several different PCM's for 4th Gen LT1 cars. Are you certain you purchased and installed the correct one?Comment
-
The way you explain it sounds exactly like what it's doing. It shifts very hard into second and third and then stays in third. The only thing I know about the new unit is I took in my old one and they supposedly matched it up with the new one. I bought it from Bumper to Bumper though so who knws. I tried dealing with them and they told me there was nothing they could do. Do you know what numbers should be on it if I looked? By the way I really appreciate your help, your the only person I've talked to so far that had a clue what was going on. Forgive my assholeness above.Comment
Comment