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tamaz, Subaru master technician
Category: Subaru
Satisfied Customers: 1250
Experience:  Subaru certified,ASE Master technician,25 years experience
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Did head gaskets on 06 2.5i engine idles rough and shows

Customer Question

did head gaskets on 06 2.5i engine idles rough and shows codes for misfire on all 4 cylinders
JA: Thanks. Can you give me any more details about your issue?
Customer: replaced gaskets because they started leaking from using wrong coolant. checked timing belt timing belt is good, replaced spark plug wires since one broke when taking heads off
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Submitted: 1 year ago.
Category: Subaru
Expert:  Mike V. replied 1 year ago.

Hi there,

When you say the timing belt is good, do you mean you didn't replace it or the timing marks are lined up?

were the heads machined?

Customer: replied 1 year ago.
timing is still good replaced around 15,000mi ago timing marks are also good. didnt machine heads did compression test and all cylinders look good all between 150-175
Expert:  Mike V. replied 1 year ago.

When the marks are lined up, where is the woodruff key pointing? Like 3 o'clock or 6 and so forth.

Is it possible for you to send a pic of your marks? With the compression it sounds like it should be good. That makes it seem like a coil issue or perhaps the plug wires are possibly crossed?

Customer: replied 1 year ago.
woodruff key is at 6 o'clock, cam timing marks are at 12 o'clock.checked the wires thinking I did just that. car ran fine before is it likely the coil would go bad while sitting for 2 weeks car does have 140,000mi
Expert:  Mike V. replied 1 year ago.

I wouldn't expect the coil to fail just sitting there to be honest, but it sounds like you are spot on with the timing marks to me. Compression is good.

The only other thing I think could or would cause this is if you missed a ground wire someplace. I see no other reason for the problem of misfiring on all 4, especially if you didn't do any adjustments and just swapped out the gaskets.

unless there is some issue with the new plug wires causing problems with the plugs..

I'm sorry, I may not be able to help from here and if you would like I can open this back up for the other experts.

Customer: replied 1 year ago.
thank you. That's what I'm thinking if you could leave it open maybe someone else has run into this before
Expert:  tamaz replied 1 year ago.

Hi,I'll see if I can help,please check the bulk head harness connector located on passenger side for poor connections we find sometimes this harness gets pulled/stretched etc..while doing head gaskets .Sometimes while the car is running you can manipulate this harness and create or diminish the rough idle and misfires.Check it out and let me know ,thanks

Customer: replied 1 year ago.
I actually tried that today I went around and wiggled/manipulated the harness at every sensor and at the main connection an didnt have any luck. clean MAF sensor since I run a K&N wanted to be sure oil didnt cause my problem. tested the coil and it tested with in spec 10.9k. did notice when wiggling that my throttle body is humming when I turn the ignition on and when I activate the pedal that the motor on the throttle body sounds a lil crunchy. another symptom I had failed to mention is that when I rev the engine and release the pedal the engine stalls as soon as the rpmsget below 1000. I did end up getting the engine to idle smooth with no misfire by unplugging the knock sensor.
Expert:  tamaz replied 1 year ago.

Remove and check egr valve ,the valve could be hanging up causing this problem ,once you the valve removed you can see if the valve is sticking by moving it with a screwdriver.

Customer: replied 1 year ago.
I'll give it a shot this is my first vehicle with an egr
Expert:  tamaz replied 1 year ago.

Ok let me know,I'll be back tomorrow evening.

Customer: replied 1 year ago.
checked the egr it functional cleaned carbon build up since I had it off. friend mentioned his wrx had the same problem when he got it serviced and the valves were adjusted. checked my valves they were at .0025 so i adjusted to .006 and the problem is solved . thanx for all the help
Expert:  tamaz replied 1 year ago.

That great news,glad it's fixed!

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