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Discussion Starter #1 (Edited)
Greetings!
I need some help with the GM3800 Series II in my girlfriend's 2004 Buick Regal LS. I've done some searching and have some ideas but I think it would do me good to start a thread specific to this motor's symptoms. Below is chronological order:

-"Low Coolant" without low coolant or over heating. O2 Sensor code. Ignored :)icon_roll)

-Intermittent misfire on cylinder 5:
Changed the oil (black as night), replaced the O2 sensor, replaced air and fuel filters.

-O2 Sensor code remains, random misfire (P0300):
Replaced the plugs and wires on the front bank; noticed minor corrosion on the coils. Plus were noticeably worn but still had good gap. Wires had resistance in spec. (It was 95 degrees and I had other things to do so I left the back bank for a more comfortable time). Misfire goes away.

-Runs fine for a month, back bank got put off. Random misfire:
Replaced back bank plugs & wires.

-Runs fine for a week, intermittent misfire. Current codes:
P0102 (Intermittent MAF)
P0134 (O2 Sensor)
P0141 (O2 Sensor)
P0300 (Random Misfire)

So before I discovered the P0102 code today I had read it was likely the ICM. I am leaning towards ruling out coils because I personally have never seen, heard of, or read about an intermittent coil failure and now I have MAF issues.

So here are my options:
-MAF
-ICM
-????

What I don't understand is how replacing the plugs and wires fixed the issue temporarily. As a side note, I thought I smelt coolant near her heater core yesterday. It was faint and gone today. It may have been a vehicle parked in that parking space that was leaking coolant before me. Again, coolant isn't actually low and it isn't over heating, though it is due for a good flush (something I will get to once I figure out this misfire). She has neglected the car until it started having issues and now I am in a labyrinth of maintenance issues and otherwise. It could very well be a number of issues arising in quick succession.
 

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1)Try gapping plugs closer. .045-.040

2) Corrosion at coils- not good

may have to replace coil due to corrosion

Use di-electric grease at tip of coil and tips of plugs...very small amount ONLY!--- too much will cause boots to slip off.

3) O2 sensor code could be caused from misfiring cylinder

4)Swap coils to isolate a bad coil- I had a failed coil once

5) check fuel pressure anyway-

6) possibly flaky ICM - less likely but possible

No Fun dealing with a maintenance ignored car_ Good Luck_ let us know what you found out...cheers
 

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7) Clean MAF sensor - preferably with electronic contact cleaner
 

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Discussion Starter #4 (Edited)
Thanks. I am cleaning the MAF, running some fuel injector cleaner, and topping off the coolant today. Tomorrow I will try and hit it before it starts getting too hot to try tightening up the gap in the plugs a bit. Maybe swap the coils around (I wish the ECM could nail down which cylinders are actually misfiring). Couple of questions regarding spark plug gap:

Is the factory spec 0.060 too large?
Wont decreasing the gap decrease plug life and potentially lead to random misfires on its own?

Also, how do I check the fuel pressure on this engine? I dont even have a Haynes for it.
 

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Discussion Starter #5
Cleaned the MAF, cleared the codes, drove it around the block a couple times, still misfiring but MAF code did not trigger.

The only codes triggering now are P0134 and P0300.

In reference to swapping coils: Since the ECM cant nail down which cylinders are misfiring and it is random I dont think moving the coils around will do anything. I guess I will be doing some junk yard pickin'. I wonder if there are any open around here tomorrow.
 

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Tightening the plug gaps to .040 will not decrease the life of the plug. The tighter gap will require less voltage to jump the gap. I am running around .040 because nitrous really boosts the cylinder, and you do not want misfires when hitting nitrous.
 

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Discussion Starter #7 (Edited)
Pulled the plugs, tightened the gap to 0.050. I didnt want to go any tighter for fear of ruining the electrode. No change.

However!

While driving around I figured if I pull the plug wires on the coil one by one I should always notice it getting worse unless it is the coil that is causing the misfire. Sure enough, pull the top coil's wires and there is a lot of clicking and it is clearly running even more rough. The same goes for the bottom coil. The middle coil shows no change and there is no electrical clicking. So, I believe it is the center coil.

No salvage yards open today. She's ready to hit up Advance Auto and get some new ones. The car has a blue book value of $1500...no way I am letting her spend $200 on three new coils when it is $30 at the yard.

I'll report back if this solves the issue. Thank you for your help.
 

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Discussion Starter #8
Coil fixed it though it still has an O2 code. $24 at O'Reilly with a 1 year warranty.


I am crossing fingers this lasts her long enough to get into a new car with a warranty...or that it at least waits to break down in the fall. :icon_conf
 
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