Single Cylinder Misfire

[stkelly]

I have an 08 Mercury Mountaineer with 102K miles and the 4.6L v8.

I've been trying to track down a random shudder at idle for a little while now. After the engine warms up I'll randomly get a shudder when I come to idle. When I'm driving I occasionally feel a miss but I definitely notice the shudder after coming to a stop and waiting at a light.

I'm not getting any lights or codes. But when I check real time info on my scanner it is showing that cylinder 1 has misfired 300 or so times within a short drive cycle. All the other cylinders show either 0 or 1. I assume maybe 1 misfire on the other cylinders is ok.

I've already moved the COP from 1 to 2 and the real time still shows cylinder 1 as the issue. I replaced the plugs at 64K miles so I wouldn't expect any of them to go bad in 38K miles. The engine was rebuilt at ~69K: A shop made a mistake during a repair and blew a hole in the valve cover. (http://www.explorerforum.com/forums/showthread.php?t=390513)

At this point I assume I should try a new plug and see if I stop having the issue. But is there anything else that could be causing the misfire on one specific cylinder? I do have a knock noise at hot idle. Seems like it may be that dreaded cam phaser issue. Along with an occasional burning oil smell from the 1-4 bank side of the engine. Both of these last issues seem to come and go in waves.

Thanks in advance for any insight.

 

[Themightyquinn]

To rule out ignition as the issue, I would swap the cylinder 1 plug and wire with another good cylinder. Also check the spark plug gap and inspect the overall condition of the plug. Reset the PCM by disconnecting the battery and see if you still have the issue. I would also use a stethescope to check the injector and a noid light tester for the injector electrical connector. Another option is to do a compression check on all 8 cylinders to see if maybe that one cylinder has low compression (not as likely, but work a try). I am suspicious of the shop who rebuilt it. How long was the work warrantied for? And how long after it was rebuilt did the misfire begin? Funny it didn't trigger the CEL.

 

[Flag Gibby]

Quinn, the V8's have COPs so you cannot swap the "coil wire" and the OP already swapped COP #1 with #2 with no change in the issue. Also, the V8's have to be missing very bad before you get a misfire code on them which makes it hard to troubleshoot unless you watch the live stream of information like the OP has done.
If non motorcraft plugs were used when they were changed then it is quite possible to have one already failing, champions are notorious for failing quickly. I would just swap the plugs between #1 and #2 and see if the problem migrates to #2 . It is quite possible to have a plug fail after only 38k miles of use since motorcraft only warrantees the plugs for a year. As far as an oil smell, check to make sure that you don't have a leak in the valve cover again that is putting oil on the hot exhaust manifolds and that the manifold on that side (passenger side) does not have any broken studs on it.

 

[rocko107]

Same symptom/issue on my wife's 2006 EB Explorer with the V8 at about 100K. Both my nephew(who owns a shop) and my self assumed it was either a plug or a coil. After putting in new plugs the issue persisted so we moved on. There is no easy way to diagnose witch coil it might be so I just had them replace all the coils . Issue was solved and I don't have to worry about another coil going later on. Worth it since the rig still drives almost like new.

R.

 

[stkelly]

I'm going to try a new plug in cylinder 1. No sense in moving them around especially since I have the version of the head where the plugs stick. I'll post back the results. I'm pretty sure it's not the coil on plug since I moved COP 1 to cylinder 2 and the misfire stayed at cylinder 1.

 

[Themightyquinn]

Quinn, the V8's have COPs so you cannot swap the "coil wire" and the OP already swapped COP #1 with #2 with no change in the issue.

Sorry. Was wondering what COP meant???? I have the V-6. But there are general troubleshooting guidelines that u can use on almost any engine. Still trying to figure it out on my other explorer.

 

[Flag Gibby]

Sorry. Was wondering what COP meant????

COP = coil on plug