Hi all! Long time listener, first time caller

I first experienced this "shuddering" about a month ago while on a long drive and passing someone on the interstate. When I floored it to get around someone I felt something like missing. Thought it was perhaps a bad tank of gas or something. Got busy doing other things when I got home and forgot about it.

About 2 weeks ago I had a no start condition and had to have a tow home. Reading a bunch here led me to believe fuel pumps so I replaced both last week and success, she lives again (thanks for all those that posted the how-to's on that!). I figured that was what the shuddering/miss was all about if the pumps were near end of life (160k miles).

Tonight on the way home from another long drive, noticed the shuddering again. With new pumps (airtex), socks, and filter I'm hoping like crazy it's not a defective pump. Could be the secondary is bad or electrical issue? How best to test the voltage supply side to see if it's one pump or the other? If I pull the relay on the primary will it start and run on the secondary to see that it's ok? Not sure when the secondary comes on or if it's all the time.

What other things should I be looking for? Coil pack? Clean Mass air sensor? I'm definitely thinking of plugs as I bought it used with 100k and it now has 160k and have not replaced them yet. I'm hoping someone can help me narrow it down so I'm not throwing the kitchen sink at it as I don't have much time to play in the garage these days.

Normally I can search around here and find something that answers my Q's but the threads I've found either didn't have the same exact issues or the suggestions offered didn't have a conclusion post as to whether it was fixed.

Thanks in advance!

 

Seems like the best place to start would be plugs. You need NGK iridiums.

good luck

 

Hmmm, just noticed my signature didn't post, it's a 2002 XJR.

I'll pick up some plugs tonight, what gap?

 

They should be around the 1mm mark - use the NGK IFR5 10 - and while you're in there, check the plug wells for any traces of oil, a leaking spark plug boss seal can lead to a short and misfire.

 

Ifr5 10... There appear to be some varieties. D10, n10, etc. maybe that's heat range? Also they appear to be about $14 per plug and hard to get except special order here.

This plug is easy to come by: BKR6EIX-11
Thoughts?

 

Also check for a air leak, no codes?

 

Nope, no codes... That would make it too easy

 

Wow, are you sure its a misfire? because that would create a CEL on.

 

Not sure it's a misfire at all. Just feels like a miss. Had a similar problem on a couple of previous supercharged/turbo charged cars where there wasn't enough spark to handle heavy boost situations. Once it was a bad plug wire another time it was too large of a gap on the plugs. Kind of hoping it's just plugs and not a pump failure after just one week. Pulling the tank was a PITA.

If it were one of the pumps, can I troubleshoot like this:

Pull the P1 relay (per this diagram from JagTechOhio)...
R
R P1 R R
P2
... and see if the second will allow the car to to start and run to test that the secondary pump is working? Then pull P2 relay and do the same to test the primary pump is working? I don't know if both pumps activate to prime the system when key is initially turned to ON?

 

**edited**

I'll bet there's oil down the plug wells, this is why you're not getting a CEL...

 

So you think a hotter plug would be better? I'm sure you guys have some personal experience to vary from the factory but just want to be sure. Looks like factory is saying colder and a wider gap for the XJR.

Found this in the JTIS:

Spark Plug Type
(Leaded markets - service fit only) NGK BKR5E-11
Normally Aspirated NGK PFR5G-11E
Supercharged NGK PFR6G-13E

Spark Plug Gap mm (in)
(Leaded markets - service fit only) 1.0 - 1.1 (0.039 - 0.043)
Normally Aspirated 1.0 - 1.1 (0.039 - 0.043)
Supercharged 1.2 - 1.3 (0.047 - 0.051)

I found this handy chart for decoding the NGK plugs as well:
http://www.ngksparkplugs.com/techinf...tnumberkey.pdf
Though I'm sure it's been posted here many times before...

 

I think so too.

Pull the coils and if there is oil on the tip of the rubber boots, then start with that.

You going to need new valve cover gasket and grommets.

Make sure you get the correct year gaskets, I believe the 1998-99 have gray and orange ones, the rest are the same.

 

@ srt, yep that's the right plug, I've edited my post so there's no confusion. I haven't used those plugs in 5 years.

 

Cool, thanks for the advise guys. I'll get some plugs and take a look tonight if I can spare some time. Any thoughts on this testing scenario?

 

So I picked up my BKR6EIX-11's tonight but unfortunately had too much work stuff going on to change them tonight (supposed to rain tomorrow and my other car has no top).

I did test the pumps, adequately I think. For my car at least the relay configuration in the trunk is:

R
R P1 R E R
P2

Where E is an empty slot as opposed to the diagram I had referenced earlier.

I pulled P2 first and got normal start but "Restricted Performance"
Heard a fuel pump running but was wondering, what if a clamp had popped off the pump? Ran it for 5 min or so to be sure it wasn't just fuel in the rails keeping it that way.

Shut if off and put P2 back in and pulled P1. Interestingly enough, no "Restricted Performance" Now that's odd. Primary fuel pump not responding and no warning? Went to the owners manual to confirm relays and of course I get the oddest excuse for technical writing:

R1
R1 R1 R1 R1 R7
R1

R1 Fuel Pump S/C only
R2 Heated Rear Window
R3 Tail and number lamps
R4 Fuel Pump
R5 Stop Lamps
R6 Accessory socket (Where fitted)
R7 Auxilary +

So according to the Vehicle Care guide portion of the owners manual we XJR folk have 6 pumps dedicated to our S/C. Comforting

So over to the JTIS...
Found this:

FUEL PUMP 1 RELAY BROWN BUS RELAY #4, TRUNK FUSE BOX / TRUNK

FUEL PUMP 2 RELAY BROWN BUS RELAY #1, TRUNK FUSE BOX / TRUNK

So I'm thinking it must run as follows:
R3
R2 R4 R5 R6 R7
R1

Which would thankfully make sense. (Hopefully the technical writer of our manuals was on just the medicinal sort of substances) So in typing this it's run on just the secondary pump now for at least 10 min as I'm a slow typist so I suppose both pumps are working even if I can't verify to what volume.

Hopefully with some time this weekend (or no rain), I can pull the coil packs and plugs and cross fingers for the solution.

 

So I changed the plugs Friday night using BKR6EIX-11 versions. I did in fact have a little oil in driver side #2. I think I'll wait until I need to do the chain tensioners or something to correct it. It wasn't a LOT of oil...

I took it out for a test Saturday and she pulled strong from 65 to 90 mph with no hesitation. Went back and cleaned the MAF and throttle body for good measure and washed out and re-oiled the k&n as well.

I noticed that the blade in the throttle body was not completely vertical when I lodged the gas pedal all the way down so I could clean it. Stumbled on this thread so I will give it a go later today.

https://www.jaguarforums.com/forum/x...d-38663/page3/

Thanks all for the advise so far!