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tamaz, Subaru master technician
Category: Subaru
Satisfied Customers: 1211
Experience:  Subaru certified,ASE Master technician,25 years experience
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2005 Legacy Wagon: Check engine light comes on when car runs

Customer Question

2005 Legacy Wagon: Check engine light comes on when car runs rough, shudders and loses power and speed at the same time the cruise control light blinks on and off. At first, this problem was intermittent, but the last time I drove the car it was continuous.
Prior to the last use, I drove the car to a local shop and it performed perfectly on the way. The mechanic was unable to find the problem with a diagnostic computer perhaps because it was running fine at that point.
I’d appreciate your insight.
Thank you,
Neil Stewart
Submitted: 1 year ago.
Category: Subaru
Expert:  tamaz replied 1 year ago.

Hi,did the shop retrieve any diagnostic codes at all?There could be many things that could be causing this most of the time something in the secondary ignition ,like the ignition wire ,spark plugs or the coil are you aware if any of this was checked?

Customer: replied 1 year ago.
I don't believe there were any diagnostic codes retrieved.
The mechanic did examine the wires in my presence and found no problems.
I don't know if the plugs or coil were checked although I suspect they were.When I left the repair shop the car operated perfectly (as it had when I dropped it off the previous day). The next day on a short ( 5 mile) trip to town everything was fine. However on the return trip the problem returned and continued until I turned the ignition off at home. That is: the check engine light came on, the cruise control light blinked on and off, the car ran rough and shuddered.So, what's the likely culprit?
Expert:  tamaz replied 1 year ago.

Hi, if the coil and plugs are good we have a the possibilities of a few things, injectors,headgasket, valve guides out of the 3 I mentioned the valve guides and the injectors would be the most likely that would cause a intermittent failure.The tech really needs it in it's failed state or at least a diagnostic code to follow,I have many guesses but guessing cost too much money,now that the check engine light is on the system should be scanned so hopefully a code can be retrieved and the diagnosis can continue.From my past experiences I've found most times intermittent misfires were caused by valve guides that have come loose and it's always the exhaust that are the problem.If you can get the code I can be of better help ,thanks for your time.

Customer: replied 1 year ago.
I can't get the codes before next Monday (8/24) when the car is next scheduled to go in the shop.
Expert:  tamaz replied 1 year ago.

No problem,I'll be here!