Hi Guys,

I was driving last week - stopped at a red light - noticed a miss. No big deal, probably a coil on it's way out so I thought.... I hooked up my Matco Determinator and sure enough - the misfire malfunction message flashed "yes" intermittently when the miss occurred.

Yesterday, I whipped out the COP tester - I pulled the coil covers off and test each coil at start up.

All coils checked out normal cold (driver's side bank - 100%) except Coil #3 - seemed off compared to the others. So I thought, OK...good. (No oil in any of the spark wells)

I let the engine warm up to operating temp and drive - sure enough, the misfire was back.

I test each coil again (at operating temp) on driver's and passenger banks. Driver's side - 100% normal

Passenger side - Coil #3 now seems ok - Coil #4 (less than 10K miles - OEM) was acting up, so was Coil #2 and Coil #1 - couldn't isolate the coil causing the misfire when the message came across on my scanner. (No CEL light by the way)

When I say acting up - I mean the COP tester was beeping and flashing rapidly as though the coil was firing off more than the norm.

Today, the replacement coil came in (Ford Motorcraft - OEM) placed it in Cyl #3 - all OK until the engine warmed up - same issue with the miss. Started switching out coils on the passenger bank - same issue, seemed worse though - put all coils back in their original spots, except #3 - left the new replacement in place.

Seems like the coils on the passenger bank are wacky when the engine is warmed up. The miss is definitely on the passenger side bank.

On a last thought - I could have sworn I picked up a faint scent of coolant by the cam cover on passenger side today. (But coolant recovery tank - full, no loss of fluid) No over heating whatsoever - coolant temp was steady around 200 - 205 degrees yesterday.

Engine runs well, just a miss at idle when warmed up and when decelerating from highway speed.

I'm thinking:

* Cam sensor?
* Tensioner?
* Wiring to the coils?
*Head gasket?
* New replacement coil - defective (doubt it)

Needless to say, the Jaguar is "out of commission" until I get the cam cover off and inspect further - I am going to inspect the spark plugs also (They are new NGK double platinum)

Any thoughts or feedback would be appreciated. Thanks!

 

I would check the wiring on the passenger side of the coils. Tough to do really but with your high miles it might be worth cutting the harness apart and running the car that way to troubleshoot.

Less likely but has been reported is electrical noise induced into the wire harness tripping up the coil firing signal. I can't remember where the noise was coming from in that case?

Have you ever done any repair to the wires or plugs to the coils?
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No repairs to the harness, wires or coil electrical connectors. My thought was maybe the harness is chafed somewhere behind the motor.

 

tbird6 - pulled the coil wiring harness apart on passenger side - I got my hopes up when I found some of the wires hard - however after removing the hardened electrical tape - looks like the neg side of the coils are all spliced together if that makes sense.

Nonetheless, I clipped the hardened wires and re-connected all using a weather proof butt splice. I also pulled the cam cover off - no issues with tensioner and the cams flats are aligned perfectly.

Put everything back together and same random misfiring issue. No CEL light either - just feel the misfire then the "yes" flashes on the scanner - now it sounds like misfires are coming from both banks. COP tester is leading me no where!

In looking at JTIS Electrical - I noticed each bank is connected to a ignition suppression Capacitor - wondering if this could be my issue or possibly the camshaft position sensor olr maybe it's time to invest in 8 new coils. (Bummer cause at least 2 have less than 10K miles and I just installed a new one yesterday)

Any feedback as to where to look next would be appreciated.


This is driving me bonkers.

 

Have you plugged in your OBDII reader and taken the car for a run to see what might come up? Another area to look in are the injectors, if one is fouling it would give you the same symptoms. Just a thought.

 

Hi Gus - Yes, my OBDII reader has been hooked up - no injector faults noted - no DTC's either. I did take a drive - all seems normal, except for the misfiring - just weird how the Coil On Plug tester is not picking up on the intermittent misfiring.

I have run Techron fuel system cleaner every so often.

I went back out this morning and when I ran the diagnostic - I now pull up a P0302 - Misfire detected. It must be pending as the CEL did not light up.

I have another coil on order - I will replace Cyl #2 upon it's arrival and update.

 

Good troubleshooting!
Let us know what you find. Anyway you could get all 8 coils to a Ford dealer with a coil stress tester? The test is easy to run on the machine and most of the cost is in removing the coils.

I bet it's a flakey coil at this point.
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Using the OBDII like that will give you pending codes that can point you in the right direction that is why I recommend to do it. As for the injectors keep in mind they do not always throw codes when beginning to fail. I like many replaced the coils on an entire side when I get one that fails they seem to go at the same time.

 

Any chance it's cat(s)?

 

I just got this very cheap tool for checking your coils. It's only about $11 at most parts stores. I think it's too cheap to NOT have one. KD #2756

Maybe get one and check all your coils?


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Gus, good thought regarding the injectors - I'm sure they are original - If changing out Cyl #2 coil doesn't yield an improvement - I'm going to focus on the injectors next.

tbird6 - Now, I'm seriously thinking about changing out the other coils - I can also get the coils to Ford if need be. I guess when one coil goes they could affect the durability of the others (over time) - thanks for the pic of the coil tester tool.

JagV8 - I don;t believe it to be the cat - that is why I'm not driving her until the misfire(s) are sorted out.

Thanks for all the feedback - I was getting worried no one had $0.02 to share with me...

 

The coil tester I posted came from KD and they have now updated the tool so it's easier to see the spark.
Same price and part number just make sure it says for HEI ignitions. They have a standard one with less gap to jump and that won't stress our coils enough if they are marginal.



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This is the one I use

Link http://www.autozone.com/autozone/acc...questid=138015

But I am leaning towards this

Link Heavy Duty Spark Plug Tester - Teng Tools Australia

 

I like that second one. You can adjust the gap which is the main difference between the HEI and standard versions.
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tbird6 - how about 2 flakey coils - one of which being the NEW one I installed the other day!

Here is how I found this out... The other new OEM motorcraft coil came in unexpectedly early this afternoon to my surprise - I ran out and installed in Cyl #2 - started car.

P0302 went away. Car was running somewhat better than at warm up - the misfiring was back - not as bad though.

With the COP tester went through each coil for a good minute - coil by coil and #3 stood out. I said "that can't be - it's the new coil, what if...." - I pulled out the original Cyl #3 coil I removed the other day - installed...

And viola! Misfires gone.... (for now...)

Lessons learned:

1) Just because it's new doesn't mean to automatically rule it out.
2) Leave COP tester on each coil for at least 60 seconds.
3) In my haste - I started switching coils - don't do that!

Positives out of this dilemma:

1) Re-wired the passenger side coil harness. (wires were hard and melted)
2) Found water leaking from the cowl onto the engine harness (weekend project)
3) Finally got around to replacing the cam cover gasket - passenger side. (Jaguar - OES gaskets and O-Rings) as I knew I had a small oil leak at the lower rear corner of the cam cover.
4) Secondary tensioners and guide rails - nice and solid! Nice and clean - no oil/gunk build up (should have snapped some pics...)

I will take her out for a good drive Saturday to confirm - but after a short 10 minute drive today fully warmed up - no more misfires.

Thanks everyone for all your help.