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Still chasing misfire gremlins


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As mentioned in previous threads I have been chasing misfire gremlins. 850cc DW injectors were tested, cleaned, rebuilt and re-tested. 3 are pratically identical but 1 is a little higher flow. That was put in cylinder 4 since supposedly it can run a little hotter. Code remained misfire cylinder 2.

 

That did not get rid of CELs so I installed new coil packs. CELs immediately went off. Short test drive and still feels a little rough and idles a bit low for comfort - feels like it wants to die stopped at idle.

 

Hooked up Romraider and there is still a misfire on cylinder 2. It is showing teens-30 range at idle and as rpm's increase it goes way down to 2-3. All other cyillinders showing zeroes. Does that symptom give anyone an indication of what the problem might be?

 

That nagging misfire has me completely baffled. What do you think it could be and since it almost goes away on higher rpm's. Even if it isnt anything to worry about it isnt right.

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I'm assuming you did a vacuum leak test. You replaced the coil pack, but did you change the plugs? ... If not, try that, and do a compression test while you're in there. Cross the worst scenario off the list (hopefully), and then put it back together, changing the air filter and spraying down the MAF sensor with cleaner. If the misfire persists (is it temp dependent?), you could be looking at any number of things, maybe something simple like OCVs or maybe not. I chased a cylinder one misfire for a while, turned out to be a HG.
LW's spec. B / YT / IG
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Did a pressure test and smoke test recently. Only thing found was OEM intercooler had a small crack. Since replaced. Prior to this (March?) when it was running really bad, pressure test found a bad valve. Had both heads decked and all new valves & springs installed so burnt valve is not likely and I sure hope it's not a head gasket!

 

Air filter is pretty clean. Ill spray the MAF but since this has been recurring in that same cylinder something tells me it is something there. Maybe I'll swap injectors in 2 & 4 just to see if anything changes. That will at least eliminate that one variable.

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Well those tests aren't free. :lol:

 

I'm going to swap injectors around one last time. If that is not it then I guess I bite the bullet, put it in the shop and tell them diagnose it and quit blaming injectors.

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The spark plug is in good shape ? A new plug is a few bucks. You may have a bad one, not every plug is perfect.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Yup. Have pulled them twice to inspect them in fact. All look good and gap is good. I am hoping it's not a bad wire or something weird like that. Then again I would be ecstatic if it was... it would mean I finally solved the issue! :lol:

 

I don't want to take it back to the shop that did the headwork. Their anti DW injector stance just turns me off. OK, their tuner doesn't like them but you can't automatically blame them for an issue without properly diagnosing it, particularly since I have had them serviced and flowed. They are working fine. I will know with 100% certainty when I get a chance to swap 2 & 4 and see if the misfire follows.

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Have you change the position of the spark plugs ? The plug may have an internal issue that keeps it from working perfectly. Just trying to keep it cheap.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Take our all of your coil packs and reach in with needle nose pliers and twist the flat connectors slightly one way and reinstall them. The plugs become loose after 10 years or so and by twisting them slightly, it renews the contact between the female connector and the male spades. Put a TINY bit of dielectric grease on the plug on the females before you put them back on.

 

This has fixed a LOT of misfire issues.

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He may be talking about the male tabs in the connector from the harness. I know someone played with them once and the problem went away.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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New coil packs-old coil pack plugs. The female spade connectors become loose over the years and if you twist the flat spades on the coils slightly, it causes a slight interference fit and will regain lost contact, like spreading an extension cord male plug ends to get better contact in a wall socket. Twisting them just a tiny bit makes them kind of scratch their way on when you put the plug back on and that scratch regains the contact.
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