Cylinder 5 misfire even with new coil !

[Dustin Gebhardt]

I had an intermittent misfire in my #5 for a while. I moved coils and plugs around and it always stayed with cylinder #5. I replaced the pigtail to the coil and the issue was fixed. I have replaced almost all of the other pigtails after that. Most of them had the rubber ring/gasket torn or brittle. This would sometimes keep the pigtail from snapping into place, likewise the brittle plastic clip broke off on several of the plugs.

 

[K-Rom]

If all the other recommendations don't work, do a dry and wet compression check on that cylinder.

Low compression will be reported as a misfire.

 

[Doc Doug]

Move coil packs then check to see if cylinder misfire followed coil. If not, swap plug wire to see if misfire followed wire. If not replace spark plug. If still misfiring, check wiring at fuel injector. If good, consider compression testing. If all cylinders within 10% then replace that one fuel injector.

The key is to perform tests to attempt to move the problem to another cylinder which will identify that problem.

Absolute worst case, you have a bad head gasket or intake manifold leak at that cylinder.

 

[07navi]

Or a bad valve.

 

[pennyanguy]

OK, moved coil packs around... misfire stays on #5... I can not seem to remove the plug... dont want to put too much load on it as these are new plugs (200 miles ago had a "top notch" local shop replace them) so I think I may let the shop that replaced them check that one... they seem to be really in there... a few questions though... and thanks for all the advise so far.

-#5 cyl is forward most drivers side? want to make sure I am working on the right one.
-plugs are 9/16 socket???
-using 3/8 ratchet... I am soooo worried about breaking one... all I read are horror stories about doing that... should I try with a 1/2 ratchet? breaker bar? how tite should they be??? I am probably overthinking this but dont want to get into an issue where I have broken more then was broken before...

Pigtail plug looks near on perfect... like I said before this truck could pass for new its so clean (not because of me... old owner was a 70 year old judge in Chantilly VA... truck was driven by a driver and parked inside all the time).. rubber is all soft an pliable, plastic nice. how would I change out the pigtail?

 

[Dennis_H]

You could still have a bad plug. I chased the same issue after a plug change. Had one new plug go bad after about 2 weeks. Thought it was coil, changed that, etc. Replaced plug with another Motorcraft one and all was fine. It's not impossible that the new plug is an issue.

 

[07navi]

OK, moved coil packs around... misfire stays on #5... I can not seem to remove the plug... dont want to put too much load on it as these are new plugs (200 miles ago had a "top notch" local shop replace them) so I think I may let the shop that replaced them check that one... they seem to be really in there... a few questions though... and thanks for all the advise so far.

-#5 cyl is forward most drivers side? want to make sure I am working on the right one.
-plugs are 9/16 socket???
-using 3/8 ratchet... I am soooo worried about breaking one... all I read are horror stories about doing that... should I try with a 1/2 ratchet? breaker bar? how tite should they be??? I am probably overthinking this but dont want to get into an issue where I have broken more then was broken before...

Pigtail plug looks near on perfect... like I said before this truck could pass for new its so clean (not because of me... old owner was a 70 year old judge in Chantilly VA... truck was driven by a driver and parked inside all the time).. rubber is all soft an pliable, plastic nice. how would I change out the pigtail?

They won't break unless they are the original 2 piece ones from 2005 to 08 +-. Squirt some penetrating oil in there, let it sit overnight, and then get out the 1/2" drive ratchet wrench (not when cold).....yes 9/16"

 

[JExpedition07]

The new SP-546 2 piece plugs don’t break, they have a lot more crimps. Wrench on it all you want it ain’t breaking.

 

[07navi]

The 515 plugs won't break either but you have to pull one out to see what's in there.

 

[CaptOchs]

Could be a bad PCM? I had that happen on a Dodge Charger when I replaced plug and coil. I was screwing around a lot like you're doing. I had to take it to the dealer.