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NGK plug differences?
Posted 31 August 2014 - 11:40 AM
Posted 31 August 2014 - 07:25 PM
could still be the wires (check that they're tight on the plugs). have you re-set the CEL? (FLAPS or disconnect the battery for a few minutes). have you checked the wires to the injectors?... once had this happen when a mouse chewed through the shielding of an injector wire.... good luck.
Edited by later, Peter, 31 August 2014 - 07:26 PM.
Posted 31 August 2014 - 11:34 PM
Have you pulled the plugs to check their condition? Possible the number 4 plug is damaged or fouled.
Posted 01 September 2014 - 01:18 PM
Posted 01 September 2014 - 01:19 PM
Posted 04 September 2014 - 06:36 PM
Ok, finally got around to pulling the plugs.
Cylinders 1, 2 and 3 looked identical, almost brand new. Cylinder 4, however, looked like it had been through a war. Carbon build-up, flaky grey matter. I put a new NGK plug in and drove the car about 5 miles. The rough idle is still there and the CEL is flashing for the misfire and eventually came back on steady. I pulled the new plug and it looked horrible. Worse than the plugs which have been in there for 3 months.
A friend came over with his compression test kit and what we found is not promising. Cylinders 1-3 had a solid 170 across the board. Cylinder 4 had 60. Another friend who has Subarus came over and he thinks a burned valve, as he had the same thing happen on his 2000 Legacy GT.
When the heads were sent out to be surfaced for the head gasket job 3 months ago, shouldn't they have checked the valvetrain for any issues? I would think they would. My friend who did the compression test said it could be a burned valve or a build-up of carbon not letting the valve close fully. He suggested running some B-12 through the gas tank and see if that breaks up the carbon/cleans out the intake & exhaust valves before resorting to pulling the head again.
Any thoughts on this? The Forester is in great shape with only 124,000 miles on her. We want to keep it, so willing to put some more money into it, if necessary.
Posted 04 September 2014 - 10:12 PM
Most machine shops do not check for valve issues unless you specifically ask them to. If you just ask for a re-surface, that's what they'll do. The process for checking cracks, leaks, and valve seat issues, is more involved, and you'll typically be charged $20-40 per head for that.
Burned valves are most often due to incorrect valve lash clearance. Pull the galve cover and check lash clearance on that cylinder. If any valves have zero lash the burned valve theory may be correct.
Seafoam/ intake system cleaners only really work if the cylinder is actually firing. The compression in that cylinder is too low to ignite the AF mixture and burn away the oil and carbon in the cylinder, thus the buildup of crud on the plug.
Posted 05 September 2014 - 09:13 AM
Posted 05 September 2014 - 01:22 PM
Seems to me there is 'incomplete' combustion and a seafoam or similar treatment thru a vacuum line 'could' help. Might be a waste of time but.....?
It would be nice to have some kinda borescope pics of the inside of that cylinder.
could a dropped valve guide be an issue? might be able to spot after dropping the exhaust.
Posted 19 September 2014 - 11:30 AM
Is it time to take the car back to the guy who did the work and have him take the head off again?
Posted 21 September 2014 - 05:08 PM
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