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Northstar #1 Misfire


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Hello all:

My first time doing a forum so here goes. I have a '97 Deville with a '99 engine in it. About a month ago i picked up a minor miss thru all ranges. Within about 3 weeks time it turned into a full blown Cyl. #1 misfire. I have enough knowledge to be a little dangerous so here is what I have tried so far:

Swapped plugs with known good one no change

Installed one new wire on that cyl. no change

Swapped coil pack with another one no change

Compression check over 100

Installed one new injector no change

Cleaned grounds at ICM no change

Checked for Vac leaks couldn't find any

I have tried everything that my 20 years experience has let my think to check and the problem stays at the #1 Cyl. it does not follow the parts around to any other cyl.

I have always repaired my own equipment, but this one is kicking my butt!!! I really like my (Daddylac) It is my first one and hopefully not my last but I'm going to need some help on this one. Thanx for your time. J. Johnson

Hey guys, I forgot to add that when I pull the wiring plug off the injector at #1 it seems to make no difference in the engine performance. Does anyone know how to check the trigger there? is it just voltage or what?

Edited by mech444
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:welcomesmiley: Welcome; I move this from the NS Performance Vendor forum to the main discussion forum.

Check the miss diagnostic chart in this post: http://caddyinfo.ipbhost.com/index.php?showtopic=14378#

Bruce

2016 Cadillac ATS-V gray/black

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how did plug look when you took it out? what was compression reading? over 100 is vague. i would expect 140 on all cylinders. what is compression on cyl #3? misfire could be wet plug, bad cam lobe, cracked valve seat. you changed many things but there are still other things to consider. try new plug, not used.

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how did plug look when you took it out? what was compression reading? over 100 is vague. i would expect 140 on all cylinders. what is compression on cyl #3? misfire could be wet plug, bad cam lobe, cracked valve seat. you changed many things but there are still other things to consider. try new plug, not used.

Hello:

Plug looks like cylinder is lean, not wet really. If I remember from a week ago the comp. was 123ish. Did not check any other holes yet.

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The integrity of the #1 injector circuit needs to be checked. One lead should have full battery voltage when the ignition is 'On', and the other is grounded momentarily by the PCM during cranking or operation. A current-limiting resistor and an LED could be placed across the terminals, in series, to verify this activity, however, this would not place much load on the PCM driver and may not reveal all possible failures. Assuming all the replacement parts are functional, and the circuit integrity is verified, all that remains is the PCM.

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The integrity of the #1 injector circuit needs to be checked. One lead should have full battery voltage when the ignition is 'On', and the other is grounded momentarily by the PCM during cranking or operation. A current-limiting resistor and an LED could be placed across the terminals, in series, to verify this activity, however, this would not place much load on the PCM driver and may not reveal all possible failures. Assuming all the replacement parts are functional, and the circuit integrity is verified, all that remains is the PCM.

I love answers like this.

Bruce

2016 Cadillac ATS-V gray/black

Follow me on: Twitter Instagram Youtube

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The integrity of the #1 injector circuit needs to be checked. One lead should have full battery voltage when the ignition is 'On', and the other is grounded momentarily by the PCM during cranking or operation. A current-limiting resistor and an LED could be placed across the terminals, in series, to verify this activity, however, this would not place much load on the PCM driver and may not reveal all possible failures. Assuming all the replacement parts are functional, and the circuit integrity is verified, all that remains is the PCM.

I love answers like this.

Thank you for your input. Do you know where the pcm is located on a '97 deville? How much money would I be looking at? or will a used one be the way to go for now?

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RockAuto lists remanufactured PCMs ranging from $97 to $227; these would need to be flashed with a calibration based on the VIN. It is possible that a used PCM from a similarly equipped DeVille would work; the worst case is that it would need to be programmed too.

The 1993-99 Northstar features a waste-spark ignition system, using 4 coils for 8 cylinders. If the ICM fails to fire one of the coils, two cylinders would be affected. An internal coil short was ruled-out via substitution with another unit. In the case of the newer Coil-Near-Plug Northstars, it would be possible for the ignition control to fail in a manner that would affect one cylinder, as the 8 ignition events, over the course of two engine revolutions, occur sequentially by way of individual coils.

Edited by KevinW

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RockAuto lists remanufactured PCMs ranging from $97 to $227; these would need to be flashed with a calibration based on the VIN. It is possible that a used PCM from a similarly equipped DeVille would work; the worst case is that it would need to be programmed too.

The 1993-99 Northstar features a waste-spark ignition system, using 4 coils for 8 cylinders. If the ICM fails to fire one of the coils, two cylinders would be affected. An internal coil short was ruled-out via substitution with another unit. In the case of the newer Coil-Near-Plug Northstars, it would be possible for the ignition control to fail in a manner that would affect one cylinder, as the 8 ignition events, over the course of two engine revolutions, occur sequentially by way of individual coils.

Good Morning Kevin: Do you know if I can unplug my PCM and check for corrosion or such without doing any further damage or getting locked out? Should I be disconnecting battery while screwing with this PCM

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