I've read the forums, the electrical manual wiring diagram and Alldatadiy to try to solve this issue. Temporary restricted performance and misfire DTCs.
2004 XJR, no mods. Replaced all plugs less than 1000 miles ago and seemed to be fine. NGK 5464 IRIDIUM BKR5EIX-11 PLUGS GAP 0.040
Happened again P0300, P0304,6,8 and P1314. Replaced 4, 6, and 8 coils yesterday, E1019 Carquest by Intermotor. Test and got P0304,6,8 and 2 now +1314. Clear codes and try again. P0304,6 and 1314. Occurred at almost exactly 5000 rpm in 3rd. Watching speed on previous runs and this rpm would seem to correspond.
So, this is left bank only. The manual shows only electrical T/S procedures for these codes, so am I safe to eliminate fuel and air? 10 tests per coil. For one coil-ok, but 4 coils? Electrical diagram shows two common wires for the coils, but common to all 8 not just 4. Fuel and air would be common to all 8. There are no other codes shown for air or fuel.
Hoping maybe a Jaguar tech can point me to something common on the left bank 2-8 that would cause all 4 coils to randomly misfire.
I'm thinking of selling the car and don't want to sell it with a problem like this, even though it only happens at full throttle when passing. All help appreciated.

 

Hi independent Jaguar shop owner and mechanic here.

A common cause for multiple misfire codes on this engine is due to vacuum leaks. Only way to find all the leaks is with a smoke machine . Do you have any sort of scantool to monitor live data for the fuel trims? I can go over a few common spots that cause vacuum leaks. The engine oil dipstick has an oring on it. Pull out the dipstick slightly and push it back into the dipstick tube. There must be some resistance when the oring hits the tube indicating a seal fit. If the dipstick goes in and out freely with no resistance felt at the oring there will be a huge vacuum leak here. Its a simple fix just replace the oring. another spot is the orings failing on the plastic crankcase valve that is on top of the passenger size valve cover. It can be hard trying to match up these orings i would recommend just replacing the whole valve. This is an easy repair aswell. The next common spot is where the plastic brake booster pipe enters the throttle elbow underneath the throttle body. There is a plastic sleeve and oring that must be replaced and this is not easily accessible unfortunately. Its not a matter of if these 3 spots will fail its a matter of when. If these havent been fixed already atleast once in this cars lifetime i would highly suggest looking into these 3 spots.

monitoring the fuel trims under certain conditions is the only way to determine exactly what is going on here as well and getting the engine smoked. If a smoke test reveals no leaks and fuel trims show fine at idle but show lean under acceleration i would suspect the outlet duct plates leaking under boost. There is always a possibility of a bad MAF aswell but not as common as vacuum leaks.

If you have any questions you can email me Edmundce@gmail.com

Edmund Jr
Edmunds Jaguar & Rolls Royce service
Palm Desert, CA

 

Thanks, Edmund, Jr. for the answer, the suggestions, and the kind offer. I'll see if I can check those out. Fuel trims are probably beyond me. The one thing you mentioned, the outlet duct plates leaking under boost, occurred to me as well since that could affect just one side. I'll see how far I can get and I may well take you up on that offer to email you.
Appreciate your help.

Dale

 

Maybe worth knowing that a "huge" leak nowadays can be quite small - everything's got tighter tolerances!

A really big leak and it won't even start...

 

You are correct, JagV8. It doesn't take much. I guess I'm having a hard time grasping the idea that a leak would only affect one bank. Seems like I'd be getting codes on all cylinders and something other than just misfire codes. The only solutions/checks for those codes are electrical. I've got to find the time to dig into it and I'm not excluding anything. Thanks for your input.

 

A couple of thoughts. May be affecting both banks but not enough to throw equivalent codes on both. Or (more often) may be something that's specific to the one bank - bad cat, leak at a valve only one one side, etc.

Many use an elm327 and look at fuel trims. Cheap and quite easy. So cheap that if you can't figure it you're not out much.

 

Still trying to figure this one out. The following are the readings with the last P0300 code set.
FUEL SYS 1 OL-DRIVE, FUEL SYS 2 OL-DRIVE, CALC LOAD % 89, ECT DEG F 197, STFT B1 % 0, LTFT B1 % 12.5, STFT B2 % 0, LTFT B2 % 9.3, FUEL PRESS PSI 70, MAP (inHg) 27.7, ENG RPM 5157, VEH SPD MPH 93, SPARK ADV. DEG 17, IAT DEG F 48, MAF LB/MIN 40.206, TPS % 100
The thing that stands out is the 27.7" MAP reading at WOT. Shouldn't be pulling anywhere near that vacuum. Replaced the MAF, wasted money. Checked air filter - clean. Removed WOT aux air flap in air box. Have yet to test again.
If anyone sees anything else abnormal in these readings, any input is appreciated. Trying to avoid removing intake plenum and possibly more searching for a leak.
Thanks for reading.

 

I'm really surprised it can figure a P0300 at that time. Well, any OL time.

is that the freeze frame data?

 

Similar problem recently with my '04 XJR. Misfires and temporary restricted performance would only occur under hard acceleration on a long steep hill merging onto a highway near my house. Restricted performance would clear after pulling off the road and waiting a less than a minute.

Local repair shop was able to reproduce the problem while monitoring and identified that one cylinder bank was causing misfire codes. Fuel pressure checked OK. Turned out that exhaust back pressure on one side was 2lbs, and less than 1lb on the other side. Catalytic converter replaced. The mechanic also said that the plugs showed signs of being overheated and required replacement - these were OEM plugs that I personally replaced about 40k miles ago.

Got the car back 2 days ago and performance back to normal.

I found this thread since I was starting to search for normal exhaust back pressure since I will likely soon replace the other converter.

 

Errr......the recommended plugs are 8-NGK IFR5N10.

 

Yes, JagV8 that is the freeze frame data. Yes, meirion1 the plugs I used showed up as equivalents to the IFR5N10. The new plugs appeared to cure the problem initially. I had codes on both banks. Now it is only bank 2 and only under full throttle. mdrag, I'm beginning to wonder about cats and O2 sensors.

 

If the plugs are OK, cat would be next suspect I think.

 

You can use a lit cigarette if you don't have a smoke machine...Don't laugh it works...Maybe not the safest way!

 

Is this relevant?

https://www.jaguarforums.com/forum/x...-issue-154370/

 

Actually, I do have access to a smoke machine, so I'll try it viper1996. And thanks for the link meirion1. It certainly seems relevant. I can't believe it would be that simple, but I'm willing to try anything at this point. Thanks to both of you.

 

If the PCV valve is sticking or indeed other air/vac leak you'd expect fuel trims to be out at various revs especially on one side. Have they not been checked?

 

Yes, JagV8. The fuel trims are listed above; LTFT bank 1 12.5% and bank 2 9.3%. I don't know if that is significant or not. None of the freeze frame data seem out of place except 27 inHg @ WOT. I replaced the MAF, cleaned the K&N filter, and removed the auxilliary air flap in the box. No difference.
Meirion, I read the link you provided but the misfires are all on bank 2 and the PCV is on bank 1. I found one loose hose clamp at the flexible connection to the metal intake tube, but tightening it didn't help. Now I get the restricted performance shutdown, but it won't set the check engine light so there is no freeze frame data, only the P0300 and 02-08 cylinder codes. Seems to me any intake leaks would cause misfires on both banks, not just Bank 2. Leaning towards the O2 sensor on that bank or the cat, though no codes or odd readings have been shown on the O2 sensors. No misfires noted at any other time other than WOT. Even if I bought some bad spark plugs, all one bank?

 

I think you're not seeing what I meant. "... at various revs" meant check at various, not by any means just freeze frame data.

Idle, is the main thing to look at!

 

JagV8,
At idle the fuel trims are within tenths of a percent of each other. There are no obvious indications of trouble when checking Live Data, on the road or idling. There is only the problem at WOT. No misfires, no codes under normal driving.
Thanks,
Dale

 

Something such as a blocked cat, then.