EJ255 cylinder misfire

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EJ255 cylinder misfire

Postby skidaddle » Wed Aug 16, 2017 9:13 pm

Since I bought the 07 liberty gt it had a broken clip on cylinder 4 plug to coil. Maybe once every few months I'd get a P304 (cylinder 4 misfire) code so I'd crawl under, pop it back on, all good. It started getting worse so now I've replaced the plug, and it's doing it every 20 minutes! Swapped coils, changed plugs, problem still there. Still plenty of power but runs rough on idle. Next I'm considering swapping injectors and getting some upper engine cleaner. Hoping it's not the loom or ECU. Also assuming I put the 3 pins back in the correct location for the plug. As I'm sure it wouldn't run at all if it is wrong. Anyone have a wire diagram or any other ideas? Thanks
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Re: EJ255 cylinder misfire

Postby Lane » Fri Aug 18, 2017 8:24 am

Have you check your AVCS solenoids?
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Re: EJ255 cylinder misfire

Postby bigBADbenny » Fri Aug 18, 2017 10:10 am

How old are your plugs?
Log the car with tactrix, vagcom, btssm using romraider on pc or btssm on android.
Log the avcs vvt angles at 1500rpm static and on the freeway.
Look for vvt inactivity or oscillation between banks.
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Re: EJ255 cylinder misfire

Postby skidaddle » Tue Sep 05, 2017 10:17 pm

Had low pressure in cylinder 4 due to excess carbon build up and a crack in the piston. So I've had the heads removed, inspected, machined and am mounting them back onto a new STI short block. This has not been a cheap exercise. But I'm confident I'll have a decent engine now for years to come.
Thanks for your input guys.
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Re: EJ255 cylinder misfire

Postby bigBADbenny » Wed Sep 06, 2017 8:44 am

Sounds good, pity it was an almost worst case scenario, but at least your sump wasn't full of metal from a spun bearing etc?
A conservative street tune and monitoring via eg btssm and regular oil changes would be advised for continued reliability... :)
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Re: EJ255 cylinder misfire

Postby skidaddle » Sun Sep 10, 2017 10:14 pm

Thanks Benny,
This btssm you speak of, I see it's an app and you buy the hardware separately. Does this allow you to do a street tune on the original ECM or would I need to upgrade this too?
I've been doing the oil changes every 5k already so that's no issue.
Cheers!
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Re: EJ255 cylinder misfire

Postby Surge » Mon Sep 11, 2017 1:33 am

To load a street tune you need a tactrix 2.0 and a laptop.
Plus romraider and ecu flash.
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Re: EJ255 cylinder misfire

Postby bigBADbenny » Mon Sep 11, 2017 7:07 am

Once you're tuned, btssm is a convenient method to log and have virtual gauges...
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Re: EJ255 cylinder misfire

Postby skidaddle » Wed Sep 13, 2017 10:29 pm

Thanks guys.
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