Ok fixed ALL the vacuum leaks no more 171 all good then all the sudden only at high rpms and into 3rd or highway tromps into passing gear all 4 cylinders 2-4-6-8 misfire, good gas, great fp, new plugs and coils. Runs like a dream otherwise. Searched until my fingers bled all I can find is knock sensors, clogged cat on that side, and o2 sensors, found a forum where someone switched upstream 02s and the problem followed that side. NEVER does it on 1-2 shifts at HIGH rpm ever. If I hold 2nd and run it out it happens too, pings then restricted performance.

Anyone?

 

Sorry to hear. The first thing that comes to mind is a knock sensor. Detonation is usually a result of too of low octane rating , poor timing, or carbon buildup. Since its on one bank it's most likely the knock sensor.

 

ty im going to try the 02 sensor swap first since its easy. I have to read live data. Shocking no one else had this issue with this car and posted a definitive fix.

 

ping only happens when your on the high r's 2nd gear and beyond then rp hits. Really points to cat.

 

Perhaps, but I still lean more toward an issue with timing. My experience with bad cats were associated with power loss. What year is your car?

 

2004 no power loss just that high rpm issue it seems to nose over lose power and ping then rp. Runs perfect, feels like its running out of fuel but the pressure is fine. You google 2-4-6-8 misfire a MILLION cars had this issue and not one ever says what fixed it lol.

 

If it were timing it would be all the time.

 

Just for giggles....check your ignition capacitor at the rear of the LH cylinder head.
With all of your delving into the air leaks you might have a damaged wire or left that unplugged.
It removes spurious noise from the ignition coil supply voltage which could be giving a weird feedback into the coils. There is no logical reason it would pick on just one bank to cause global misfires, but high RPM only....it could be a factor.

 

I agree with h2o2steam. My Super V8 had no end of strange misfires and shifting problems. No definitive codes. I threw a lot of parts at it and was about to file for divorce. The last thing I did was swap out the ignition capacitor AND the one mounted to the bottom of the transmission, and a set of OEM coils (made in Japan). I can't say for sure which of those things solved it because I did them at the same time but the car has been flawless ever since. (We have been happily married for 6 years now and I love her more each day). The capacitors were cheap and easy to swap so I would certainly give it a try.

Jeff

 

I would definitely check the engine grounds. I can't remember for certain, but I think I read some time ago that each bank has its own ground, which may also cause things like the cap or the knock sensors to misbehave on only one bank. I still think it might be a timing issue caused by the knock sensor.

-j

 

Never even heard of this you know where it is?

 

I already redid all of them years ago esp behind the headlights

 

Oh I just read each bank has a ground? You know where they are?

 

Anyone???

 

All codes are drivers side, then a code P1316 and P1314

 

I would check G30

 

This thread might be helpful. I don't have time to read it at the moment.

 

This diagram from that thread shows the relationship between the grounds, the cap, and the coils.

 

YES I see but where does one get a capacitor? I looked all over the web and see no Jaguar ignition capacitors for a 2004 XJR

 

have you checked the special bolt that doesn't interfere with the readings on the knock sensor is in the correct place at the top/back of the valve cover on the relevant side?