So I know this sounds like an easy one but I'm stumped. Changed the plugs over the weekend and finally got around to a test drive today. Getting misfires on cyl 4&6. Both on the driver's side of course, which is the hard side. However all coils are seated and plugged in, nothing was missed as far as I can tell. Anyone have any suggestions?

 

Possibly improper gap, and I've also seen where too much dialectic grease (if it was used) can interfere with the ability to spark.

 

Pulled the plugs and gap is fine. Reinstalled everything and issue continues. I can put the coil off the plug with the car running and hear the coil firing (pop pop pop) but car doesn't seem to run any worse with the coil off the plug?

 

Duff plugs ?

 

Tried the old ones, problem still there unfortunately

 

what codes do you have, any injector codes

 

P0306 and 0304 as well as a random misfire code of p1350
​​​​ thanks

 

Did you mix up the wires/coils or knock connectors loose on ECU?

 

Nope, all good there. What I didn't realize is how tight the coil boots fit and how little leverage there is to seat them so I'm thinking those two coils aren't properly seated. Hoping.

 

I'd be moving the coils to different cylinders to see if the issue 'moved' with the coils.

And yeah, if the connections are 'tight', look inside to make sure a metal connector hasn't been pulled out of place.

 

Hi Doc Oc,

Sorry to join your thread late. A few possible causes I can think of are:

1. Did you use the correct OEM plugs? (I don't see that you have told us the year, model and engine of your car)

2. Did you apply anti-seize compound to the plug threads? Today's plugs do not need anti-seize and the compound can add resistance that interferes with spark (and leads to over-torquing the plugs).

3. Was there oil in the spark plug tubes? If so, oil baked onto the spark plug port threads can add resistance that interferes with spark.

4. Were the plugs properly torqued? Loose plugs will cause low compression and misfires.

5. Are the coil wires in good condition? The insulation on the coil wires can harden and crack, leading to shorts or broken wires.

6. Is it possible a crankcase breather hose or vacuum hose was damaged during the plug replacement procedure? Leaks in hoses can cause the bank to which they connect to run lean, resulting in misfires. Have you checked your fuel trims?

Beyond that, Carbuff2's idea of swapping coils with non-misfiring cylinders would be a good next step to rule out coil failure.

Cheers,

Don

 

Thanks for the detailed response. I'm hoping it's fixed now but with the hurricane in the SE I haven't been able to test drive. Going soon now that the sun is back. I think the coils just weren't down all the way and some weren't making a good connection. Seems too simple but I didn't have any grease and leverage is tough so hopefully that's got it.

 

So I am down to one cylinder misfire. I did lose a plug and have to buy a replacement on Amazon so possibly it was no good. Problem is I am seeing several different answers for which cylinder is #4 on my V6. Anyone know for sure?

 

Problem is you still haven't told us the year, model and engine (supercharged or normally aspirated) of you Jaguar...

 

Oh thought I mentioned v6.

Normally aspirated?

 

It's an F-Type V6 which by definition is supercharged, being the AJ126.
Very little difference over the model years, same OEM spark plugs for all.

 

So turns out, as often seems to happen to me in car life, the problem wasn't even spark plug related! Just so happens that while I have been working on the car over the last month, the solenoid for my snow WMI system had failed. No check valve so every time I started the car it was sucking in a ton of meth, causing misfires. Finally got a boost sensor code which I have seen before when the wmi sprays at too low of a boost level and floods things. Removed the meth and car runs like a top. How weird! But thanks so much for everyone's input!! Heading to the mountains and Tail of the dragon tomorrow so I was in a huff! So glad to have it running

 

Actually, he never even told us it was an F-Type (he still hasn't), so all we can do is guess that he is in the correct forum. But at least we now know it has the Snow Performance water-methanol injection system... Might have been helpful to know in Post #1...

 

Well it's the f type forum and I'm a senior member so I thought that was a given😁 But I did mention v6 above.

 

Senior Member just means you've made a sufficient number of posts to no longer be a Junior Member. You might be surprised at how many senior members post multiple questions in the wrong forum until we figure it out.

It's very helpful to visit your User Control Panel and edit your signature to include the year, model and engine of your F-Type so this information appears in all of your posts so other members can give you the most accurate responses.

Thanks for reporting back with the cause of your misfires. This is how we all learn!

Cheers,

Don