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Sudden rough engine w/cel, brakes, traction control&cruise control flash


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Yesterday while coming home (Only 5 miles) my 2011 Legacy 3.6R all of a sudden started running really rough, and my CEL, Brakes and Cruise control started blinking with the traction control on steady. Had the OEM codes read and it came up with cylinders 4, 5 and 6 misfiring. I would understand it if it was either a right or left bank that failed but not 4, 5 and 6. Never had a single problem with this before. Any idea's? Much appreciated, in advance!
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Where are you located? If you get winter weather it could be a wiring harness that got chewed through by woodland creatures using your car as shelter.

 

I'd check for broken ground straps and the like to start. I now there are one on the bottom front of each head and I think there's another above the bell housing.

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There are a lot of possibilities, bad coil packs, bad plugs, a wiring issue as mentioned above, bad fuel, an intake leak. All possibilities to look at. If you can, eliminate as many possilities as you can before taking the car in for troubleshooting. What we have seen with cars in northern climates is coil packs separating and then failing in temperature extremes. You should also check the condition of the battery and the ground connections on the engine.
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Some follow up questions that will help us identify the issue:

 

Where are you located? A member may be local to help out if they see the thread.

Were the codes that were pulled pending codes?

How many miles are on the car?

What maintenance has been done?

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Do you have a habit to or have recently ran the tank dry and drove on empty for 10-20+ miles?

 

Given the age of the car and probable mileage and state of maintenance,

you most likely have a few clogged injectors as a result of:

 

a. bad / contaminated fuel - all it takes is one tank or less (debris got past the pre- and in-pump housing filters, to the fuel rails and into the injectors)

b. running the tank to nearly empty recently (and sucking up debris from the bottom of the tank into and past the pre-filter and in-pump-housing filter)

 

Getting to the injectors on the H6 is fairly easy.

Follow the vacation pics for steps to release fuel pressure (engine bay fuse), removal of the injectors. Before you swap or replace anything, with the engine running unplug the power connector from #6 and #5 and see if the engine stabilizes and runs less rough (at least for an H4). You can even disconnect an entire bank (2,4,6) and see how she does.

 

From there you can play around with swapping injectors if you can isolate ones with an issue, see if it follows.

 

Next up, some new injectors (don't bother ultra-sonic cleaning them) and fresh set of gaskets (there are three per injector, all cheap). Best price for the stock Denso greens is ~$80-90/each.

 

Might as well replace the in-tank paper filter (it comes with the housing) and pre-filter while @ it.

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Quick update; It was the #5 and #6 cylinder ignition coils. The #5 was flat out cracked and the #6 was showing signs of delaminating. I ended up replacing all of the coils and decided to replace the plugs while I was there (110K miles). The plugs actually looked pretty good. The car is running good again. Probably going to have to change the damned things in my wife Tribeca too. Of note, I found a youtube video that showed a very easy way to change out the coils..... its not as easy as he made it look!
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It gets easier the 3rd or 4th time around. Glad it was something simple. There is a gent with a tribeca chasing his tail on a misfire, the regulars on that page are pretty sure it is the ecm he is trying hard to prove us wrong, lol.
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