Rikthoven

Here's the symptoms. Misfiring at low idle(engine warm) consistently and under acceleration inconsistently. Discovered a burnt spark plug wire for Cylinder 4 a week ago. Replaced the wires and sparks. Misfiring still happening but again only at low idle and sometimes under acceleration. I'm sure the bad wire put an uneven load on the coil while it was working on failing, which it never did actually fail but it certainly looked like it was working on it. When I start it in the morning cold (at or below freezing here now), the car idles perfectly fine course it's idling at a higher RPM than it would warm. Once the engine begins to come up to temp I start noticing slight misfires under acceleration at highway speeds. When I come back down to idle with the engine warm the misfiring is really obvious. It's not missing every RPM but missing enough that it's obvious that it's happening. The misfiring is not enough to consistently throw a code usually, why I don't know because it's obvious that it's happening. It did throw one over the weekend and it said misfire cylinder 4, which was the cylinder that previously had the bad wire.

So the misfire feels like it's a couple cylinders here and there. It would be helpful if the computer would throw another code to see if it says Cylinder 4 again or a different cylinder. So I'm left guessing. My guess is it's possibly the coil. Any help or suggestions would be great. Thanks!

Lethaldosage423

if you have all new plugs and wires then there is a very good chance your ignition coil is going bad. its a pretty common issue.

If your worried about spending the money and that not fixing it, do a compression test first. You could have a burned valve or bad rings. That would be worst case. probably a coil

IvanRad

do the compression test kit costs over 15$ , you can check all ur other cars in your future too. do you have a tuner? check for codes? disconnect battery yet ? i think either one of your wires might be mixed up ? what kind of sparks did you buy and what kind of wires.

Update: you could also have a bad alternator if your battery levels are going up and down during this "misfire" mine luckily was a bad battery

JimC

The 4.0 uses a waste spark and if you mixed up wires when you replaced the wires and plugs you can get the symptoms you are describing. (waste spark meaning that 2 cylinders fire even though only one has fuel).

Since you said that you put new plugs and wires in and now have problems: it is easy to mix up the wires because the coil is in order for one bank but not the other. That often causes people to mix up the wiring. Double check and make sure that you connected them properly. The coil is marked with a number for the cylinder at the post.

Rikthoven

I guess maybe my initial description wasn't totally clear. The misfiring on cylinder 4 was present prior to swapping out sparks and plugs. The problem persists even through now I have swapped out the coil. So it has new sparks,wires, and coil and the problem is still present. It misfires at low idle and under acceleration in high gear and load, I.E. going up a hill on the highway at top gear. I checked and there is no smell of fuel in the exhaust at idle. I also tried spraying the area around Cylinder 4 with carb cleaner while the vehicle was running and no difference in misfire was noted. So now my thought is failing injector or a valve issue? All I know is it's nasty business getting stuck in traffic with this thing because 4 misfires like crazy at idle. It fires maybe every 4th rev at idle. So it's not completely dead it's just dead enough to be super annoying.

Lethaldosage423

do a compression test on all 6 cylinders

also plug in a noid light into the number 4 injector harness and see if your getting injector duration.

JJHoover

have you checked to see if you are getting fire from the coil? you may also have an intake leak.