misfire on cylinders 2,4,6, and 8. plugs seem perfectly fine. remember being advised to go for coils if experiencing misfires. replaced all 8 since it seemed like they were all slowly going bad. still same cylinders misfiring.

car goes into restricted performance and lists misfire code when redlining at any speed. car sounds like its choking when it happens. previously had evap leak error but hasn't showed up since clearing codes after coil change. any advice on next steps?

 

Funny that it's all on the one bank's

You can hear the misfires? Or it's just throwing codes and going into RP.

This only happens above 5000rpm? Drives fine at low revs?

 

wait thats the same bank? i thought the passenger side bank was 1-4?

i dont hear the misfire. i hear stuttering then codes+ rp

no issues at low rpms

 

Codes PDF & JTIS show engine layout. 2,4,6,8 are indeed one bank (#2, since bank 1 always has cyl 1 and then they alternate on a V engine).

All 4 going bad together, on one bank only, isn't coils or plugs as I think you've now realised.

Look at fuel trims and are they quite big at idle on just the bad bank then drop if you rev for a while to around 2500 rpm? Air leak if so, otherwise you're hunting something else.

 

Yes that's all four on one bank, the drivers side on a LHD car.

I see from your previous posts that you have been having this problem since December https://www.jaguarforums.com/forum/s...fornia-133470/

A vacuum leak cannot affect just one bank because all the vacuum is prior to the supercharger and will affect both banks.

A boost leak however can affect one bank only, if you look at the duct seal on the supercharger outlet where it goes to the left side charge cooler.

But a boost leak also seems unlikely.

Other things that could affect only one bank would be the upstream O2 sensor on that side, or the cat converter, which you mention in your earlier posts.

There was a V8 X350 XJ here on the forum that was suffering from very bad misfires on only one bank, it turned out the cat had collapsed and was choking that bank.

Seems like a plausible situation in your case too.

 

In addition to the advice above, perform a visual inspection of the wiring harness to the fuel injectors on the LH side of the engine for any signs of damage or broken wires.

Has the vehicle had any work recently completed on that side of the engine?

 

Fuel trims will behave very differently for a bad cat than an air leak so at least can steer to or away from each of those.

 

I do believe some of the coils were actually bad which made some misfire codes come up back in December when I first started trying to take care of this (not all 8 tho : / ). which helps justify the one cat going bad at 64k miles. The car was smoked and no leaks were located. I will check for any damaged wiring. I did noticed a single wire going to the coils was a little worn. And it WAS a wire going to the bank in question. So there might be something going on there. There wasn't any specific work done in that area other than a mechanic a few weeks ago trying to find the leak with a smoke test and inspecting coils/plugs before giving up. I do remember being advised to check fuel trims and remembering that they were fine but that was months ago and I will try again. Thanks for all of the advice thus far. I'll start with the cat I think and see where that gets me.

EDIT: Seems like this would be important. When I was replacing the coils, I noticed the ones in the questionable bank were very hard to get into. Upon inspection, it almost looked like the chromey insides were not aligned correctly with the main opening hole (I have no idea what a lot of the terms are, sorry :/). I would pretty much have to wiggle the coils in until they forced the chromey inside to line up well enough to slide through. It was only on this bank. The other bank slide in and out completely perfectly.

 

The COP boots should be lubed with dielectric grease to ease installation. If dry they can be an SOB to install/remove.

Did you lube up the boots before installing?

Kind of sounds fun looking at that sentence!
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check the oil dipstick tube......the oring will at times cause this....make sure it is seated all the way down onto the tube. Also make sure that all lines are secure near and around the intake...from the intake elbow to bank two rocker cover,and make sure the pcv valve plate is seated properly on bank one.

 

If the dip stick tube O-ring is leaking it should set a code? I know if you start the car with the oil filler removed I get a check engine light right away.

So the car does not like any unfiltered air getting in the crankcase.
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yes it should, but it has a substituted value also...that will correct a small variation in unmetered air. I have seen leaking valve covers do the same thing cause a misfire...I just had a customer with a 2003 x type 2.5 had misfires due to the upper and lower intake gasket leak. So again, yes it should post a code,P0171 or P0174...Also if you have replaced the coils, and your fuel pressure is steady...then try the connectors, watch the metered air values...13.8-14.7 will be fine....@maf...also look at the upstream 0xygen sensors,@ closed loops see what they say ,downstream shouldn't show anything unless the cat is bad. I seriously doubt that.But back to the misfire,if connections at injectors are good and clean, ignition coils are good and connections are good, and plugs are good,fuel pressure is good, then I would look for a vacuum leak.

 

After many many months of never having time, trying many of the suggestions made on this thread, and several mechanics who all failed me, I went ahead and just took it to a muffler shop who pressure tested it and confirmed the cat being bad. Removed cat was completely clogged and had pieces falling out of it when it was removed. Cat replaced and now no more codes popping up. Now I just have to hope it passes CA smog testing since I used a magnaflow. Thanks, everyone.

 

Glad you got it sorted.

Another car with bad cats, seems to be happening a lot lately...