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Discussion Starter #1
Started having hard start 6 weeks ago, took to dealership and found no codes and nothing wrong. Truck started sputtering and check engine light came on, took it Dealership . "P0304 and P0300 Codes present in ECM misfire on #4. Replaced all 6 (original) spark plugs and cleaned throttle body drove 10 miles-no code returned." I drove the truck 7 miles next morning and started having same issue and check engine light flashing. Second trip to dealership "Random misfires stored in ECM 500 counts and lower refer to DOC 4630888, Fogged intake system added cleaner to fuel tank. Test drove 35 miles misfires did not return." Husband had asked about coil packs and they said they were "good". Drove it 4 miles this morning and it's misfiring again with light flashing, husband is out driving it right now on Expressway...WHAT COULD BE WRONG???? We've spent 600$ thus far and the problem is not fixed. Very frustrated!
 

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dont know what that Ref Doc # is...


but sounds like this is what they may have done- or part of it.


2011 Cadillac CTS | CTS VIN D Service Manual | Document ID: 2863222
#PIP5029: Engine Misfires Due To Major Carbon Deposits On The Intake And/Or Exhaust Valves - (May 29, 2012)
Subject: Engine Misfires Due To Major Carbon Deposits On The Intake And/Or Exhaust Valves

Models: 2008 - 2012 Cadillac CTS, STS
2008 - 2010 Chevrolet Cobalt SS, HHR SS
2007 - 2010 Pontiac Solstice GXP
2007 - 2010 Saturn Sky Redline
2009 - 2012 Buick Enclave
2009 - 2012 Buick Lacrosse
2009 - 2012 Chevrolet Traverse
2009 - 2012 GMC Acadia
2009 Saturn Outlook
2010 - 2012 Cadillac SRX
2010 - 2012 Chevrolet Camaro, Equinox
2010 - 2012 GMC Terrain
With any of the Following Direct Injected Gasoline Engines:
2.0 (RPO LNF)
2.4L (RPO LAF, LEA, or LUK)
2.8L (RPO LAU)
3.0L (RPO LF1)
3.6L (RPO LFX or LLT)

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:

Some customers may complain of a MIL and engine misfire. In some cases, the misfire may be more apparent on a cold start, may count on a single cylinder or several cylinders, and may or may not be felt by the driver. Upon inspection, the technician will find one or more misfire codes (DTC P0300-P0306) stored in the ECM and SI diagnosis may or may not isolate the cause of the misfire depending on whether the intake/exhaust valves are sticking at the time of the diagnosis.

This may be the result of major carbon build up on the intake and/or exhaust valves as shown below so the misfires should not have appeared until the engine has accumulated around 5,000 miles or more.

Recommendation/Instructions:

If this concern is encountered, perform SI diagnosis. If SI diagnosis isolates a valve sealing concern and/or eliminates everything else external to the engine, decarbon the engine with Upper Engine and Fuel Injector Cleaner by following the guidelines below:

Important Extreme care must be taken not to hydrolock the engine when inducing the cleaner, especially if it is induced without Kent Moore Tool # J-35800-A. If too much cleaner is induced at too low of a RPM, or if you force the engine to stall by inducing too much cleaner at once, the engine may hydrolock and bend a connecting rod(s).
1. In a well-ventilated area with the engine at operating temperature, slowly/carefully induce a bottle of GM Upper Engine and Fuel Injection Cleaner into the engine with RPM off of idle enough to prevent it from stalling (typically around 2,000 RPM or so). Depending on the engine configuration, induce the cleaner through the throttle body or an engine vacuum hose/pipe. For best results, it is suggested to induce the cleaner with Kent Moore Tool # J-35800-A (shown below).
2. Turn the engine off after inducing the cleaner and allow the cleaner to soak with the engine off for 2.5 to 3 hours (Do not let cleaner soak for more than 3 hours as remaining deposits may start to harden back up again).
3. Add a bottle of GM Fuel System Treatment Plus to the fuel tank and fill the vehicle with one of the Top Tier gasolines listed at http://www.toptiergas.com and/or in the latest version of 04-06-04-047 (USA) or 05-06-04-022 (Canada). See Bulletin 05-00-89-078 for more details on GM Fuel System Treatment Plus.
4. Test drive the vehicle extensively to circulate the GM Fuel System Treatment Plus, which will help to eliminate/reduce any remaining intake valve deposits.
5. Re-evaluate the concern to determine if it is repaired or improved at all. If the concern is improved but not repaired, it may be necessary to perform the above decarboning process a 2nd time.



6. To complete the repairs, advise the customer to only use one of the Top Tier Gasolines listed at http://www.toptiergas.com and/or in the latest version of 04-06-04-047 (USA) or 05-06-04-022 (Canada) to minimize future deposits. It can also be recommended to add a bottle of GM Fuel System Treatment Plus at every oil change as mentioned in the latest version of 04-06-04-051.
Kent Moore Tool # J-35800-A
Upper Engine and Fuel Injector Cleaner
 

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found this post on the Enclave forum-


"Called dealer ship we go to for service. They reflashed ecm August 2012 for recall 10287c to modify timing to extend life of timing chain.

He said a new flash release on may 10, 2017 upgrade per doc 4630888 or a Gm code 16na383 was to be performed after top engine cleaning to remove carbon. flash reduced fuel making system leaner to reduce carbon. Also to aid in random cold start misfires not related to a component failure. I Seached web and these numbers did not come up. cost to reflash $129. cost for upper engine/induction clean w fuel tank treatment and oil change w flash was $400."
 

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Discussion Starter #5
What you need to know? We change the oil every 4,000 miles at the Dealership, we bought it brand new and have been getting scheduled maintenance at the dealership. We had the Wave plate break on transmission, which was replaced by GM. You can drive the car below 40 mph and it runs fine, when you accelerate past 40 the check engine light flashes, acceleration is sluggish. When you start the engine it idles high and takes about 2 minutes to back to normal idle. I live in Michigan, so exposure to cold, snow, ice, salt, humidity, etc. I drive 80 miles on I-94 round trip to work 3 days a week and then short trips in town 5-10 miles round trip. 2009 Acadia SLT AWD Delivery date 6/17/09 built in 2008
 

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It was more along the lines of what resulted from the latest Expressway "test drive."
 

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I went back and reread your original post.
Says that the spark plugs where changed..... and coils were left.... as they were 'Good'.

Are these the factory coils?

2009s have issues with the coils causing misfires.
 

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I went back and reread your original post.
Says that the spark plugs where changed..... and coils were left.... as they were 'Good'.

Are these the factory coils?

2009s have issues with the coils causing misfires.
I thought the same. Did they look at the coils?

I have one coil fail on my 2008 already. I think it was around 130k miles.
 

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Discussion Starter #10
Husband just filled it up with Top Tier fuel (half a tank) and drove it 52 miles on I-94 and he said it ran good...so hopefully that was the fix. Thank you for all your information and feedback. I will keep posted on how things go from here! And yes they are factory coils. Only things replaced on this vehicle have been tires, brakes, rotors, shocks-per usual...Transmission wave plate replaced when it broke. Been very lucky with our purchase so far!
 

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I thought the same. Did they look at the coils?

I have one coil fail on my 2008 already. I think it was around 130k miles.
+1, at this point if it acts up again I would suspect a failing coil. Easy enough to test, just swap with one of the other coils and see if the P0304 code becomes P030x.
 

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Husband just filled it up with Top Tier fuel (half a tank) and drove it 52 miles on I-94 and he said it ran good...so hopefully that was the fix.
Just bad gas? I doubt it. You had been reporting "it's fine" - "it's not" - "it's fine" - "it's not" ... sounds like it's fine (right now), but it's probably headed for another "it's not".

And I'm not sure I'm the buying the carboned-up engine theory, either - at only 125,000 miles on a vehicle bought brand new.

I think something else is afoot here. What did the plugs look like when they came out?
 

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Husband just filled it up with Top Tier fuel (half a tank) and drove it 52 miles on I-94 and he said it ran good...so hopefully that was the fix. ...
This was the info needed. If the dealer added fuel system cleaner without also filling the tank, there's a possibility the misfire was caused by too much cleaner and not enough fuel being burned. Might not make sense, but it can happen. The engine is not designed to run well on a high concentration of acetone and naphtha.
 

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Discussion Starter #14
Don't know what the plugs looked like but YOU WERE RIGHT! IT'S NOT FINE! It's back in the dealership as we speak. Drove it work this morning with the same sputtering and engine light flashing. I drove 30 miles and every time I had to slow down and then speed up the sputtering started and the tachometer needle would bounce back and forth. Last 7 miles of my drive was normal. Got off work and it was delayed to start, cloud of dark gray smoke came out of tail pipe when I accelerated to pull into traffic. Same symptoms of sputtering with acceleration, check engine light stayed on. Called dealership and told them I'm coming in. Talked with service manager and he said "could be fuel injectors". Asked about the coil [acks and they said, we checked them, they are "good". They are refunding me cost of the "carbon cleaning."
 

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Because you owned the car since it was new, do you recall if this was ever done to it?

#14582A: Special Coverage Adjustment - Throttle Body - Reduced Power Mode - (Oct 7, 2015)
2009-2011 GMC Acadia - The throttle-position sensor may cause the engine to run rough, cause the malfunction-indicator lamp and/or an engine reduced power message to illuminate, and reduce the engine’s power. Dealers are to replace the throttle body assembly and gasket for Bosch equipped vehicles, or to install the throttle position sensor kit for Hitachi equipped vehicles. This special coverage covers the condition described above for a period of 10 years or 120,000 miles (193,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership.
 

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Discussion Starter #16
This was the Service from 1/11/2019 PO304 AND PO300 CODE PRESENT IN ECM MISFIRE #4 CYL/SPARK PLUGS BEYOND LIFE EXPECTANCY ,THROTTLE BODY DIRTY, REPLACED SPARK PLUGS/CLEANED THROTTLE BODY TEST DROVE 10 MILES VEHICLE RUNNING GOOD /CODES DID NOT RETURN.

This has been the only Engine service I have had done on this truck.
 

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cloud of dark gray smoke came out of tail pipe when I accelerated to pull into traffic. Same symptoms of sputtering with acceleration, check engine light stayed on.
If you mean white-ish smoke, your engine could be burning coolant that is seeping into the combustion chamber past a leaking head gasket. If you would've been able to SEE the plugs when they came out, they may have hinted at this problem. Coolant-fouled plugs can sometimes be dismissed as "clean" plugs.

Have you checked the coolant reservoir to see if it's down? Have you added any coolant or been billed for any by the Service Department? Let the engine cool down after turning it off before checking (not sure if your vehicle has a pressurized coolant recovery tank, but the cap would have a warning on it if it did ... you don't want to open a pressurized container with hot coolant as it could come flying out in your face!). Once cool, the level should be somewhere between the (lower) COLD and (upper) HOT lines on the side of the tank. If the level is below the COLD line, then you're probably losing coolant ... but maybe not enough (yet) to display the "LOW COOLANT" message in your cluster.
 

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This was the Service from 1/11/2019 PO304 AND PO300 CODE PRESENT IN ECM MISFIRE #4 CYL/SPARK PLUGS BEYOND LIFE EXPECTANCY ,THROTTLE BODY DIRTY, REPLACED SPARK PLUGS/CLEANED THROTTLE BODY TEST DROVE 10 MILES VEHICLE RUNNING GOOD /CODES DID NOT RETURN.

This has been the only Engine service I have had done on this truck.
Talk to your service adviser about the SCA and what it might mean to conditions you're experiencing. They'll probably work with you if this is the problem since the car falls within 10 years of your purchase of the car, i.e. 'the date the vehicle was originally placed in service.'
 

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I had similar issues on my 2009 Acadia. Could be the coil, but you would usually get the coil code usually if it's that. My guess would be you have a direct injector clogged. Running a can of seafoam fixed it for me.
 
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