Open your hood at night or in a darkened garage, pop the hood, start the engine, then pull the hood lamp fuse. Look for telltale sparks and arcing along the coil and ignition wires.

If you see electrical "creepycrawlies" along your wires, they're shot.

The O.E.M. Delco/Packard wires are good for 60,000 miles maximum service life. It's time to swap them out for new ones. Don't forget the wire looms and holders, too, as the old ones get brittle from engine heat and crack as you remove them.

You can purchase them online from Mid-America Motorworks (MAM).

 

This is killing me. I unplugged the battery and shot some connector cleaner in all the connectors I could find including the ICM. It still idles rough. I cleared the codes...did a diag check...no codes. As soon as I start it up SES light comes on. Run diag again H42. I replaced the ICM a few days ago. Could it be something else or are these bad out of the box alot?

 

I did start it tonight and there is no arching anywhere. If there were I would have seen it.....it's dark LOL

 

My motto is "If its not broke don't fix it"

 

I agree, not into the mods, but you have to keep the maintenance up.

 

Well replaced the ICM again last night. No change. Still error code H42. Man..... why can't it be coupled with a 36 so I knew if I should replace the OPTI again.

 

After further driving today I noticed the miss at idle is not bad when cold. When I hit around 200 deg the SES light goes out but the idle miss gets worse. Not sure where to go from here. Should return the OPTI and get another?

 

gave up and took it to a shop. They said opti and installed a new opti. Same issue H42 after the new opti. Now they are thinking PCM. What do you guys think?

 

Yeah I took my msd coil off also and went back to stock. I also moved the ICM off the block with a set of washers so that it runs cooler heats kills em. My car runs like a dream I also replaced the opti although I did get a bad one off ebay but they gave me a new one and no problems at all. I got mine from white performance very nice people and it came with updated brass terminals they claim to get them built better than oem so far so good. Best of luck with it

 

I found this info
Code 42 isnt grounded Knock sensor, its this: [color=red]DTC #42: Ignition Control Circuit Shorted.[/color:5411916891]

Id do some searching sounds to me like and Issue with the ICM. Check the harness wires for continuity and check for voltage to them and grounds. Id move that modual off the block. Heat kills em fast and the after market Icms are even more prone to this. My money is on the ICM

http://www.shbox.com/1/95_ign_system_schematic.jpg

Get a good volt meter
Disconnect the ICM connector. Leave coil connected.
Turn key to ON.
Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM.
Result should be 10v dc or more on both terminals. If you get no voltage, use the diagram and chase back toward the coil and the ignition fuse. Power for the ICM comes from the ignition fuse and through the coil, so any of that could be bad.
If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see between 1 and 4 volts ac (those are the pulses that trigger the coil to fire).

If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM or any of the wiring in between. Visually inspect all the connections you can get to for poor contact or corrosion.

 

They are parts changers. Take your time and have patience and do this yourself if you can. I went through hell but found my issues and my car is fine now. Many guys on here helped me a great deal and without them I could not have done it. I was advised against being a parts changer and so i set out to learn about diagnosing and if you go through the steps youll find the problem and a hell of a lot cheaper than when they just replace parst and cant fix it.
if you change the pcm its more money and its not like you needed it anyway mentality, especially if it turns out to be related to the icm. Did you change the coil to an aftermarket msd coil or a stock coil

 

And remember this above all; Persistence overcomes resistance.

 

I'm pretty sure my mistake was installing the MSD Blaster coil. Everything seemed fine until I installed it. It blew my ICM for sure because my car would not start until I replaced the ICM. I had the ICM tested and it was bad. Put on stock coil and new ICM. Replaced the Opti again too. Car runs, but has a bad miss at idle and throws the 42. Thought I wasn't suppose to run with an error code 42 LOL....at least that is what the manual says.

 

Have you run the diagnostic tests for the code 42 following the fault tree in the FSM?

 

I didn't but already took it to the shop. They actually went over the diags they performed with me. They are telling me it's pointing to the ECM. According to the manual the car shouldn't even run with a 42. It should shut of the injectors. Unfortunately that's not the case. It runs fine cold, like crap when it warms up and code 42 never goes away. funny thing is the scan tool shows 45 RPM even when the car is not running.

 

Before you buy parts, maybe you should try a different scanner. They have been known to be wacky.

 

Ok, I'll do my best to source one. I had wondered about that. I know my diag program for my busa doesn't show correct RPM either when I'm flashing my busa ECU.

 

Went to go visit the car today at the shop and man she is running worse than ever. They said they replaced the opti and the car did not run at all. They then put in another opti and the car ran like it's running now. The idle just goes up and down and still has the code 42. While I was there we replaced the PCM. Absolutely no change at all. So now my car runs worse than ever.

 

Weird, man. Sorry to hear it. My 94 also is throwing H42. Mine runs okay, but the idle gets stuck at like 12-1300 rpm. Give her some gas and the idle drops down to the correct speed. Weird because like you said, the manual states that the injectors are supposed to shut off. I as well have an MSD coil....until tomorrow that is LOL! I'm going to follow suit and lose the MSD coil, see where that takes me. Good luck with your car man, I sure hope they can fix it.

 

Crackersauce was yours the blaster coil or the street coil? You are the first person I have heard with a code 42 and your car is running. A code 42 according to the FSM says your injectors should be shut off.

So to summarize the turn of events:
car was running fine 100k miles
In my driveway with the help of a real mechanic (I'm not a real mechanic)
replaced:
-plugs, plug wires, opti, coil (with MSD blaster coil), water pump, belt, fuel filter.
Issue after: Car would not start, did not pull codes, no spark at plugs
replaced: ICM (tested bad), coil (orielly's stock type coil)
Issue after: Car started and ran fine H42 error but had a miss which got worse as it warmed up. Also noticed a little fuel on top the new fuel filter not much. Replaced ICM a second time. Tested everything I knew and took to shop.

At the new shop:
Shop tested wiring per FSM found no issues. Cleaned grounds still no issues found. Issue turned over to another tech at the shop. Tech ran FSM diags, no issues found.
Replaced:
Opti
Shop stated they noticed a hose leaking anti-freeze. Replaced hose
Isues after: Car would not start at all. Replaced with yet another Opti car starts, idle is terrible, cycles constantly still throws a code 42.
Replaced PCM - absolutely no change in symptoms. Idle is still bad, still throws a 42 even after clearing. Should I try another coil?