Cylinder 6 misfire.

[tuned]

1998 Mustang GT, automatic, approx. 75k miles. Only modifications are 3.73’s, and a PI intake manifold. When I had the intake manifold put on I forgot to specify that I wanted copper plugs so the mechanic put on some platinum plugs with new wires, which was around 5,000 miles ago. Anyways, about 2 weeks ago during a very rainy day, my car threw the CEL. So I pulled over to the nearest AutoZone and had them pull the codes immediately. Cylinder 6 misfire. So I basically just said screw it until today, the only day I had time to look into possible solutions to the problem.

So today I went out to the car and pulled out the cylinder 6 spark plug and replaced with a new Autolite copper one to see if I could get it to fire correctly. Well, this didn’t correct any problems. So since the problem wasn’t with the spark plug I moved on. While the car was running (and missing…) I pulled the cylinder 6 ignition wire from the coil pack and saw no difference in the motor movement, as in no more shaking, nothing changed it was still missing although from the wire to the coil pack it was throwing a good spark (which knocked the **** out of me). So, I then decided to swap the wires from cylinder 6 and 5 to see if it was a bad ignition wire, tested this and the wire seems to be fine, when I used the cylinder 5 wire it still missed on cylinder 6. So it’s not the wire or the plugs as far as I can see. I was told if the problem with coil pack related I would have multiple misfires, but this isn’t the case, so is it possible to have a bad coil pack causing the problem with only a single cylinder misfiring?

If it isn’t the coil pack (haven’t tested it), and it isn’t the wire or plug, what it the problem? Possibly fuel related.

Basically where do I go from here…? Anyt help, thanks.

 

[Isaac-1]

I just posted a new thread, I am having problems with water in the spark plug hole on cylinder 6 causing misfires.

Ike

 

[modmonster]

Do a compression check and see if the the cylinder 6 valves are seating. I hope for you that thats not the problrm because thats a crappy fix but it may be your problem. Either way lets hope that its not but good luck.

 

[CanadaStang]

You could try switching the injector with the one beside it. If the miss follows the injector you will know if that is the culprit.

 

[blackstalion666]

i was just gonna say that. I would look at that injector. sounds like it cuasing you problems.
and if you got spark, and you got compression and your motor only has 75k so i would think it still does. i be looking at the injector.

 

[MidnightGT]

Not to hijack the thread...but restarting mine (was deleted with crash) would be pointless...

I still have a misfire cyl 2. Should I do as he did and try switching the wires around (with someone who knows what thier doing) and try new plugs? What else can I check...? If it helps other then the light the noticable problems are rough idle and extreme performance lag...

 

[Mike97gt]

well you eliminated the wire for cyl number 6.. so the problem could be three things...


1. a injector (check with a listening tool of some sorts and listen if you hear it clicking) if you dont check wirring... if thats good replace the injector..

2. spark plug.. (very common)

3. this is the worst one... a valve not closing all the way.. this is not too common on the 4.6 but i have seen it before.. a compression check will pick this problem up...

 

[Mike97gt]

correction...

forget the plug.. i did'nt see you already did that...

check the compression.. and the injector wirring and injector itself...

if you can go too a ford dealer and use the WDS relitive compression test.. this will help pick up any valve problems... very easy too do it measures your compression without taking any plugs out

 

[blackstalion666]

another test you can do. only works though if the engine has a consistent miss. bring the engine off idle and start removing and reinstalling injector wires. what your looking for is the difference in the pitch of the engine. when you unplug a bad cylinder its not going to change as much as a cylinder that is running properly. but if your still uncertain just swap the injector with another and see if the miss fallows just to be certain. and by swaping the injector your going to cancel out that the plug, wires, and worse that the valve's or piston rings are bad. knowing certaintly the the injector is bad.