2009 Buick enclave misfire 1 3 and 5 at 45 mph and 60 mph - EnclaveForum.net: Buick Enclave Online Community
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post #1 of 12 (permalink) Old 03-28-2019, 06:47 PM Thread Starter
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2009 Buick enclave misfire 1 3 and 5 at 45 mph and 60 mph

Hello folks,
I have a 2009 Buick enclave awd 78000 miles. Runs great at all speeds except cylinder 3 misfires at 45 mph and 1 and 5 misfire at 60 mph. This the info my mechanic has seen while driving and scanning in real time. no engine light. Any suggestions before i start replacing coil packs?
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post #2 of 12 (permalink) Old 03-28-2019, 07:02 PM Thread Starter
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i want to also add that both cats have been replaced and one coil pack about 8000 miles ago to fix engine light issue.
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post #3 of 12 (permalink) Old 04-03-2019, 08:34 AM
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It's interesting that the misfires are all on the same side of the engine. I'm not sure what would cause that. Replacing the 5 other coils is a good place to start. As long as you are in there, replace the plugs too. Just adds about 10 minutes to the job and will need to be done in another year or two anyway.
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post #4 of 12 (permalink) Old 04-03-2019, 09:30 AM
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I had the same issues with my 2010 Acadia. Misfires with no CEL, then eventually ruined Catalytic Converter. Also, had high Long Term Fuel Trim on one bank.
It turned out to be excessive carbon build up on the top of the valves. The Direct Injection design, which started in 2009, allows for this carbon build up. The carbon prevents the valve from opening and shutting completely and causes misfires. The misfiring causes unburnt fuel to get out into the exhaust and, in turn, ruin the catalytic converters.

2016 Enclave Premium AWD Ebony Twilight Metallic w/ Choccachino interior , Sunroof and Trailering Package

2010 GMC Acadia SLT-1 AWD Quicksilver w/ Ebony interior , Sunroof and rear DVD
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post #5 of 12 (permalink) Old 04-03-2019, 01:15 PM
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I had the same issues with my 2010 Acadia. Misfires with no CEL, then eventually ruined Catalytic Converter. Also, had high Long Term Fuel Trim on one bank.
It turned out to be excessive carbon build up on the top of the valves. The Direct Injection design, which started in 2009, allows for this carbon build up. The carbon prevents the valve from opening and shutting completely and causes misfires. The misfiring causes unburnt fuel to get out into the exhaust and, in turn, ruin the catalytic converters.



what was the mileage on unit when the CAt finally died.

2010 FWD LT1-Gold Mist Metallic- seats 8
Build Date- July 31, 2009-2nd day of Spring Hill 2010 production.
2013 Equinox 3.6L 83,000
2010 Traverse 3.6L 148,000
2003 Trailblazer 4.2L 181,500
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post #6 of 12 (permalink) Old 04-03-2019, 03:14 PM
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what was the mileage on unit when the CAt finally died.
Well... the first Cat was replaced at about 90,000 miles by the dealer with no explanation of why the cat needed replacement. The CEL came on for the cat, so they said it needed to be replaced. I told them that I seemed to be getting declining fuel economy, but they didn't have a reason. At about 130,000 miles the fuel economy continued to diminish, and the P0430 CEL stated coming on again intermittently. I bought a diagnostic scanner tool and found that my bank 2 fuel trim was elevated and I was having random misfires, but no misfire CEL. at about 140,000 miles, the CEL for the cat stayed on. Brought the car to an independent repair shop. He said he put a scope into the engine and saw the excessive carbon build up on the valves. this was the cause of the misfiring. He recommended a chemical carbon cleaning for $300. He said it cleaned a little more that half the carbon off the valves and there were no more misfires detected. However, the catalytic converter was
ruined and needed to be replaced.
Moral of the story, if your catalytic converter goes bad, don't just replace it. Find out the reason it went bad, first, or you'll end up replacing it again. Cats don't normally go bad on their own.

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2010 GMC Acadia SLT-1 AWD Quicksilver w/ Ebony interior , Sunroof and rear DVD
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post #7 of 12 (permalink) Old 04-04-2019, 07:48 AM
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Yep, misfires are a sure fire way to kill a catalytic converter. Every misfire is raw fuel going out the exhaust port and into the cat, where the high temps of the cat cause it to burn. Doesn't take much of that to exceed the cats operating temperature range and start melting it.

I agree that it's probably carbon buildup. At that age/miles where it could be getting bad, especially if the oil changes have gone a little long or the PCV valve hasn't been kept in top shape (both lead to more oil vapor going back through the intake valves, which is where most carbon buildup comes from).
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post #8 of 12 (permalink) Old 04-04-2019, 08:52 PM
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PCV valve? I didn't see anything in the maintenance section about servicing/replacing something like that. So a 2009 Buick Enclave has a replaceable PCV valve that should be replaced periodically? What is the recommended change interval?
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post #9 of 12 (permalink) Old 04-05-2019, 10:43 AM
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PCV valve? I didn't see anything in the maintenance section about servicing/replacing something like that. So a 2009 Buick Enclave has a replaceable PCV valve that should be replaced periodically? What is the recommended change interval?

Many end up getting clogged as the holes are too small.
The part is available and you drill the holes bigger.
Some say its not even a true PCV.... but here are pics of the one in my vehicle- and the new part.


https://www.enclaveforum.net/20-engi...-thread-3.html

2010 FWD LT1-Gold Mist Metallic- seats 8
Build Date- July 31, 2009-2nd day of Spring Hill 2010 production.
2013 Equinox 3.6L 83,000
2010 Traverse 3.6L 148,000
2003 Trailblazer 4.2L 181,500
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post #10 of 12 (permalink) Old 04-05-2019, 08:17 PM
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Hi rbarrios. Thanks so much for the info regarding the PCV. Just ordered it already from rock auto. Can you pls show a picture (if you have) the exact location of the PCV for my BE 09? Thanks.

09 Buick Enclave CXL
Originals : battery, timing chain, catalytic converter, oxygen sensors
Replacements: oil pressure switch, front struts, drive shaft, rotor (once), brake pads (twice), tires (once), water seal, roof sealing (twice), transmission casing (some chip ins and dents during replacement of broken wave plates),spark plugs/plug wires (once), throttle body assy, rear struts
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