I currently have the street fire MSD coil, but I'm not starting that car again until I get a stock coil on there tomorrow. I already changed the control module, and the code remained. It's weird man, I test drove the car for almost 30 minutes, no backfiring, no misfires or misses, mechanically she runs great, but the H42 won't go away. After I read earlier about these dudes switching back to stock coils, I figure that would be my next step. I can't explain why the car even runs at all, though.

 

The ends of the spark plug wires that plug into the opti can be a real bastard to get snapped on nice and snug sometimes....I wonder if the guys at that shop are ABSOLUTELY POSITIVE that all 8 wires are connected properly?

 

good point....Ill check.

 

One thing is for sure there is a reason for this and very good point about the wires. They really can be a bitch to get on you have to hear them snap twice like a rachet. I had a bitch getting them to make that sound and if I didnt hear it and looked at the wires it would look like it was on but I knew it wasnt. You only need one to be off and youll have a miss for sure

So the car runs. Will it stay running? Is it just doing that missing etc. Witht he amount of pulls on the wires you have to check to make sure they arent broken either. I went through hell to find my issues. Replaced the opti twice replaced the icm replaced the coil and sent the ecu out to be rebuilt not to mention the countless time spent on checking continuity on all the wires from the harness to the pcm and cleaning the grounds etc. For me it was a faulty opti ultimately but the pcm and the icm had issues also it was 3 problems at once and thats why the guy gave up on the car and sold it to me. Took me 3 weeks to fix my car I honestly thought I would never fix it. Are you getting any codes from the ccm are you even checking for any codes from the ccm they can be attained by jumping the A terminal to the G terminal and are read from the instrument cluster unlike the ecu codes that are aquired through jumping the a and b terminals and counting the flashes. My car is a 1993 yours may be different depending on the year

Sounds to me like a wiring issue at this point and could very well be related as mentioned earlier to the spark wires. Hang in there Im sure youll solve this eventually

 

 

Have you tried to isolate the problem to a single cylinder? That may make diagnosing the problem easier. Could be something silly overlooked like a cracked plug. Check everything, even the little stuff.

 

I'll be heading back over to the shop tonight. I'll be pretty upset if 3 mechanics get stumped over a non-tight spark plug wire LOL. Car does run. Idle even gets better as it warms up a bit but still not right. The only code is the 42. No others.

 

Ahhh yes! CRACKED PLUG would do it.... Just a little too tight on those buggers would crack the porcelain.

 

Yup! That's why you always want to use anti-seize compound on spark plug threads going into the LT1's aluminum heads.

It's difficult enough (if not impossible) to fit a torque wrench on every one of those spark plugs to ensure proper torque.

 

check the wiring going to the temp sensor on the front of the water pump as well.

 

Crap you just reminded me I did replace the temp sensor when I put the water pump in. Would that throw a 42 if it was a wrong part? Temps seem to read fine.

 

Well, I changed the MSD street coil back to a new stock coil; and my code is gone. I'm wondering if those guys working on yours chould change all three at once (coil, module, and opti) and see what happens. As for the coolant temp sensor, I don't believe that it would cause an H42, but who knows for sure? I suppose anything's possible. If the coolant temp sensor is bad, it might cause the misfire you were talking about, but I would probably focus on the ignition components, as well as the plugs and wires. Best of luck!

 

Measure the resistance of each plug wire, they should be about 5000 ohms per foot if stock. My last new set of Delco plug wires had a wire become open circuit in one day.

 

Not to post jack or anything, however I really need somebody to explain to me the problems with the MSD Blaster coils.

I have had a blaster coil and MSD Optispark on my car for 2 years now with no problems what so ever.

Thanks!

 

We have a lot of posters that have bad experience with MSD products. What is wrong with their coils is that they aren't designed to work with the GM spark module. There isn't a thing wrong with the GM coil or the HE ignition system and why people who don't understand spark systems would think that merely changing the spark coil will gain spark energy with no other change in the spark system components is a mystery to this EE. Just because another company offers replacement ignition parts painted red does not make them better!

 

I've used MSD before in other cars with no issues. I'm using Taylor wires because I have heard good things about them. I just replaced the coil and ICM again, no change. going to try a 4th opti.

 

So other than an ICM or opti, what could possibly cause a 42 error?

 

Other than the ICM and Opti, the computer itself could throw the code, but didn't you mention that you already changed the computer once with no luck? Man, I wish I could help more. Have you changed the ICM, coil, Opti, and computer all at the same time? I know that sounds absurd, but I don't know what else to try!

 

This problem has stumped you for so long that I don't remember if you tried the step-by-step tree chart in the FSM for Code 42. If you don't have it, I can post it from the '92 FSM, could be the same.

 

42 is generally ignition related but can definitely be your computer.