Cylinder 5 misfire even with new coil !

[pennyanguy]

OK guys, need some help here. 2007 Expo EL, 105K miles... I would say Very good condition ... if that matters. This morning check engine light came on... went to autozone.. code PO305 #5 misfire... OK, easy right.. change coil pack (#5 is the drivers forward most plug right?), purge codes... comes right back on same code. Drove it yesterday, ran well. now that light is on it is running rough... so I am assuming its not a one time misfire

Seems oddly coincidental to me as in the past month (about 200 miles ago... 3rd vehicle we rarely use) I had the plugs changed by a mechanic (for 100K mile service), and Tuesday inspection was done and obviously no codes showed then.

So, if its not the coil pack, what else would I be looking for ? wiring is all pristine (this is a 100K mi truck that could pass for new)

Thinking of removing the spark plug to check it... but I have heard these can be a bear. what size wrench are they and they seem real deep in the hole... are they easy to get back in?

 

[Yupster Dog]

First try with the truck running, to wiggle the wire going to the #5 coil to see if you can get it to misfire.

Yes, check the spark plug easy to do especially if you already had the coil out. (spark plug socket and a extension you will be good to go)

If all that checks out change coil packs with the one next to it. run that for a while and see what happens.

Just a couple of thing that are easy to do and don't cost you nothing
If this doesn't find the problem at least this will eliminate a lot of things and get you closer to the problem.

 

[pennyanguy]

Thanks, Its a new coil pack but I can easily change it with one next to it to test.

 

[Yupster Dog]

Thanks, Its a new coil pack but I can easily change it with one next to it to test.

Sometimes these electronic parts are bad brand new no matter what brand you get it just happens. (had it happen to me) I spent a lot of time searching for the problem for nothing. Switching will just eliminate that.

Usually I would have done this before I bought the new one. More diagnosing and less throwing parts at it makes your wallet happy.

 

[pennyanguy]

I agree, did not even think about switching them while I was standing at the parts counter... my bad. Thanks for the input though

 

[Msport]

For me the CEL kept flashing and giving me a pending code for #5 misfire, the mistake I made was the new coil pack was not firmly or tightly fixed in place, the small bolt was stripped. I added a few washers to the bolt and it helped secure it in place. But, I had damaged the new coil pack when it was loose and I had to put an old coil pack I had as a spare.

 

[pennyanguy]

OK, I will check that... thank you

 

[07navi]

For me the CEL kept flashing and giving me a pending code for #5 misfire, the mistake I made was the new coil pack was not firmly or tightly fixed in place, the small bolt was stripped. I added a few washers to the bolt and it helped secure it in place. But, I had damaged the new coil pack when it was loose and I had to put an old coil pack I had as a spare.

why do you call it a pack?

 

[Yupster Dog]

why am I such a pack?

You spelled Hack wrong.

 

[07navi]

You spelled Hack wrong.

jerk

 

[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.