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Old 09-13-2012, 11:07 AM   #1
jerryls
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2008 Lacrosse P0300 code runs but terrible

i started a new post only because the title of the old was misleading. The car ran great then one day stalled after leaving my house only a block away and would not start but started the next day but runs terrible. I now get a P0300 and CEL is on. Car only has 70K miles. I checked the fuel pressure and it's about 60 lbs with ignition on and when running about the same. I disconnected the MAF connector and no change. What should I check next- Could it be a spark problem?
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Old 09-13-2012, 12:18 PM   #2
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Re: 2008 Lacrosse P0300 code runs but terrible

Random misfires on random cylinders!
Does weather, or water play a factor?
Does the random misfires only happen to bank1 or bank2?
*What's common to random misfires on 2-cylinders? If a bad coil pack, see www.rockauto.com
Is there any other Diagnostic Trouble Codes?
What size engine?

1 of the 4-strokes is missing on all cylinders, the question is what's common to all cylinders?

Air - new air filter, clean MAF sensor.
Metering air leak on the PCV, EGR, or air intake system.

Fuel - Fuel pressure test, fuel filter
Exhaust - Back pressure test down on catalytic converters.
Ignition - Coil, Cam, ICM, or crank sensors.

Last edited by danielsatur; 09-13-2012 at 04:48 PM.
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Old 09-13-2012, 01:14 PM   #3
jerryls
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Re: 2008 Lacrosse P0300 code runs but terrible

Thanks- I just found some other information. I checked the spark and there is no spark on wires 1 and 4(lower coil). I switched the coil pack and the problem is still on 1&4, so It points to a bad Ignition Control Module. I get 12V on the lower pin of the primary, but most likely no switching on the other pin(didnt check that, but the known good coil worked so it must be bad. Is there any other reason that would cause this? I'm thinking it has to be the ICM?
Thanks Again
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Old 09-13-2012, 02:46 PM   #4
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Re: 2008 Lacrosse P0300 code runs but terrible

It was the Ignition Control Module. I swapped it out and everything is fine. Simple job, 3/16" socket to remove the coils and a 1/4" socket to remove the connector. I bought a used one on ebay for $36.00. GM uses that same module since 1994, so there are a lot around.
Thanks for everyone's help.
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Old 09-13-2012, 04:06 PM   #5
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Re: 2008 Lacrosse P0300 code runs but terrible

Good price for the ICM, www.rockauto.com $180 , see if the Auto Parts store can bench test a bad ICM.
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Old 01-21-2016, 11:58 PM   #6
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Re: 2008 Lacrosse P0300 code runs but terrible

I just wanted to update this old post. I now have 140K miles on that same 2008 Lacrosse. I am on my 3d ICM. Apparently its a bad design. I buy the module from RockAuto for $79.00. AC delco has a newer design about twice the price which i refuse to pay. The $79 Airtech version comes with a 1 yr warranty which is good enough for me. It's a simple 10 minute job. Remove the 3 coils without taking off the wires and push them aside. The 6 bolts also holds down the ICM. BTW, I gave the wrong socket sizes on my previous post. The bolts holding down the coils and ICM are 5.5m and the one bolt holding on the wire connector is 7mm. The symptom of the failed module is that the car runs in limp mode on 4 of the 6 cylinders which is exactly what is happening.
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