Thread: Missing at 5500-6000 RPM / ICM question

Noticed that the car was missing today around 5500rpm. I have this ghetto fab creation holding my ICM to the ICM Bracket the picture from the left is ICM > plate I made > ICM bracket. The bracket came off of an L67 on to my L26. Did the S3 and S2 have different ICM's or am I just missing a piece? The "adapter plate" was made out of the old L26 ICM bracket, and is only held in with one bolt which has come very loose. I think it is the cause of the miss as any other rpm range is fine

well my first question would be have you done any valve springs to the car? i dont see any in your sig. if it is closer to 5800-6000 it could be valve float.

Originally Posted by Z34Phoenix

well my first question would be have you done any valve springs to the car? i dont see any in your sig. if it is closer to 5800-6000 it could be valve float.

I have 105# springs. I was able to fix it, the icm ground was bad. I'm Missing the L67 icm plate so I made one. It was a pos. I ran a ground from my awful icm plate to the battery and then zip tied them the the dog bone till I can order the plate from Morad or dealer. Oh and thanks for the reply.

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Originally Posted by acidcrashdburnd

Noticed that the car was missing today around 5500rpm. I have this ghetto fab creation holding my ICM to the ICM Bracket the picture from the left is ICM > plate I made > ICM bracket. The bracket came off of an L67 on to my L26. Did the S3 and S2 have different ICM's or am I just missing a piece? The "adapter plate" was made out of the old L26 ICM bracket, and is only held in with one bolt which has come very loose. I think it is the cause of the miss as any other rpm range is fine

I think my misfire in 5/6 cylinders is my fault i put AL103's in my car during the top swap.. I am gonna review the safely moding thread and see which NGK's to get.

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Originally Posted by matt5112

TR6's are still too cold for a basic top swap and even intercooled/rockers/pulley.

At least for my engine.

104's were too cold as well.

so TR55's or AC Delco Plugs?

Found TR55's at my local NAPA, gonna pick them up today and see if that fixes the issue. I am pretty sure it will.

Found the cause of the misfire. The ground for my ICM broke off the ICM bracket. Repaired that miss was gone. I threw the tr55's in so I will see how they do.

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I think I have narrowed the misfire down to a fueling issue. Looking at getting a Fuel Pump Rewire Kit to start.

First off.. yes the ICM mount plate is different on L26 to L67. Second.. you shouldn't need to add an ICM ground. There's one in your harness that connects to the end fo the block right by the ICM

Originally Posted by BillBoost37

First off.. yes the ICM mount plate is different on L26 to L67. Second.. you shouldn't need to add an ICM ground. There's one in your harness that connects to the end fo the block right by the ICM

The ICM bracket was replaced with the L67 bracket with the correct length bolts with it. The Additional ICM ground is long gone now. The misfire is a multicylinder with no preference to a specific cylinder. It comes and goes so fast. It will go weeks with out doing it and BOOM misfiring again. ICM/coils/plugs/wires all changed.

What do you mean that ground is long gone? I've done 4-5 engine swaps in a car and never hurt the ground wire. If you lost that ground, solder a new wire on or replace that damn icm harness.

Don't make me call you a .......hacker.

Originally Posted by BillBoost37

What do you mean that ground is long gone? I've done 4-5 engine swaps in a car and never hurt the ground wire. If you lost that ground, solder a new wire on or replace that damn icm harness.

Don't make me call you a .......hacker.

You can call me an incomplete detail guy, I was referring to the ground that I added. to the bottom of the plate from the battery.

Oh.. sooo what's up with the wire that GM put in the harness that goes directly into the connector of the ICM?

Originally Posted by BillBoost37

Oh.. sooo what's up with the wire that GM put in the harness that goes directly into the connector of the ICM?

Its attached to a bolt/stud on the side of the head

Then, it's well grounded and since the main ground for the vehicle is attached to the transmission/engine via a bolt holding the two together, .... it's well grounded?