Could it be the fuel pressure regulator diaphram? Maybe it is damaged and somehow letting fuel by it to get sucked into the vacuum line?

With the regulator hooked up the fuel pressure gauge slightly bounces at 44-45psi. The LTFT are about +14 and +16 (give or take a couple percent). With the regulator vacuum line unhooked and plugged on both sides the gauge is more steady at 52psi. The LTFT comes down to +6 and +7. This trim reading is very close to the last time I remember checking it on the old engine.

My only concern is that the trim is just coming down because of the increased fuel rail pressure (causing the computer to not open the injectors quite as long). Has anyone ever bypassed the FP regulator? If so, did LTFT come down like this? If I could find a way to apply vacuum to the regulator externally it would be easy to check it.

I can also data map it with the regulator bypassed, but I am not sure if it is safe to run it too long/hard with the regulator bypassed.

 

With luck someone will know what changed over those years.

 

You can use a vacuum tool from the parts store to simulate vacuum, no?

 

My 1st reaction on the fuel trims is indeed a vacuum leak somewhere, as the trims improve with less vacuum, so that should be thoroughly checked 1st imo.

Normal pressure without vacuum/pressure line attached is about 43 psi, and with the line attached at idle more like 38 ish.

 

Thanks Avos. So I think it sounds like my fuel pressure might be high since you said it should 38psi (fuel pressure regulator hooked up) and 43psi (fuel pressure regulator bypassed). My pressures were 45psi and 52psi respectively.

Vacuum: I have a boost gauge hooked up so I can report any vacuum reading at various RPMs if that will reveal a vacuum leak. I think it is about 18psi at idle off the top of my head. I had the shop that put the engine in smoke test it and they could not find any leaks. To me it did not look like a vacuum leak since the high trim seems to correlate pretty directly with load and not RPM (and the trims seem to behave differently than they did when I had a big vacuum leak). This was based on my rudimentary understanding of this stuff, but I can see how manifold pressure might be a better indicator than rpm (I still don't really have a handle on it)

Today I can take those vacuum readings (hopefully someone knows what these should be, but I will try to look it up) and log more data if it will help. I can also post pretty much any data maps or charts that would be helpful. Maybe I was premature in ruling out a vacuum leak.

 

Good idea. Those cheap ones only pull about -27 Hg though, so I think I would need a bigger and more expensive one to get to idle vac (but I may be converting something wrong). I will look into one if I don't get this figured out soon.

 

Yes, hopefully someone does know of a difference that can explain this. The shop that did it told me it is a direct swap with no differences, but I'm not sure if they know for sure. He said he had some kind of problem with an oil cooler doing a similar swap one time but that would not apply in my case, and that the rest is the same.

I did some research to verify that the injectors are the same part number in those years. So are the coil packs. I did notice a visual difference I think. I don't have the old engine but I am almost positive that the coil closest to the firewall on 1 or both sides is installed with the electrical connection facing the opposite way on the old engine. On this XJR engine they all face the same direction. I also see that the crank pulley is a slightly different design in the 2003, but I had talked to someone who told me that it was likely just a supplier change for Jaguar and that the parts perform the same.

I was also thinking that the exhaust was probably different, maybe some difference in the manifold connection, I have no idea. Maybe an exhaust leak at the manifold before the upstream o2 could do this?

 

Typically, boost gauges have the vacuum part graduated in mm Hg...

atmospheric pressure ~= 760mm Hg ~= 14.7 psi

 

You did mention to have your doubts about the accuracy of your pressure meter, so make sure you have tools that work.

When you measure the vacuum (once your engine has reached operating temp), also check the maf value (gram/sec), that could help.

 

Here are some results. All measurements were taken after I had let it heat sink for a while at full operating temp.

MAF test
PARK lb/m (g/s)
idle .67(5.06)
2500 2.32(17.54)
DRIVE
idle .74 (5.59)
1500 5.09 (38.48) (This one might be a touch low, it was hard to get a reading in the garage because it felt like it was about to overpower the brakes)
I also went back through the data logs and the most I see it flowing is a little over 300 g/s at 5823 RPM. These numbers all looked ok to me but I was comparing them to NA figures since I don't have them for sc.

Vacuum readings:
PARK
idle: 19.5Hg (this was about 17Hg on cold start, worked its way up to 19.5)
1500 RPM: 21.5Hg (when I let off the gas it briefly goes up to 23Hg and then returns to 19.5 at idle)
2500 RPM: 22Hg (when I let off the gas it briefly goes up to 24Hg and then returns to 19.5 at idle)

 

You are correct, vacuum side is in Hg, boost side in psi, thanks

 

There have been some idle maf measurements on the forum, you may have to do a search or maybe someone knows, I can't compare it with my setup anymore at least. From memory the maf reading is low, so another pointer (assuming maf is ok, as it was), to a vacuum leak.

Can't comment about the vacuum reading, as the throttle is closed down more by the ECU to control the idle, and the leak is relatively small.

 

As it looks like an air leak can you not find someone who charges less than $200 or at least someone who knows these cars or DIY (which needs research)? Having the same place do the same thing sounds like $200 wasted. Or better, point out they changed the engine and the trims are wrong so they need to redo something at their cost.

 

I was going nuts trying to find an obvious vacuum leak. None of the usual techniques were working, so I went "old school". I put a strip of paper towel in my needle nose pliers and started moving it around the likely leak sources. Found the leak in just a few minutes. Maybe that could work for you as well.

 

I think this is what I will do. The Place I had do the car is the local jag specialist, but they just keep telling me to drive it and are not interested in the fuel trim since they are about 2 and 4 percent short of throwing a code.

I think I will log a big run today and see if the guy at the shop will agree to look at the maps. If he won't, I will take it to a regular mechanic for a another smoke test. I was looking at other options since I could not find any other maps for vacuum leaks that match mine, they all look different to me and the trims are acting different than my last vacuum leak. But vacuum leaks are so common in these, I will spend more time looking for one. Thanks guys

 

FYI you can make your own smoke tester really easily and inexpensively.

You just need an airtight container you can put a plumbers smoke bomb in and some tubing, and a hand pump or small electric compressor. Have a google or search this forum. I copied a post I'd seen here and it worked a treat. The post I'd copied used a cigarette but I found the plumbers smoke to be very effective.

 

First, I can't think of anything that is really different between the 2000 XKR and the 2003 XJR engine. At least, nothing that would affect driveablilty, fueling trims or diagnostics.

Curiously, the Mass Air Flow readings you list, when compared to those I have archived and used for diagnosis over the years, seem to match up with your fuel trim maps. See the attached. Where your MAF value measures lower than mine, is precisely where your LT fuel trim is high positive. That does suggest you have an unmetered air leak. One that affects low load, low RPM more than elsewhere. Remember, under-reported air, causes under fueling. That means higher fuel trims, to add fuel.

Be advised though. Your trim values at other, higher cells, can be found on about 60% of the cars on the road that are not having a problem of any sort. Trims between 2%-7% positive are pretty common.

 

I have made no progress on this and there was no change until today. I was trying to get the monitors set so I had it at around 73MPH with cruise control on driving on the freeway. After about 5 miles I got restricted performance. I pulled codes and I had 3 pending: p1000, p300, p1316.

I know the p1000 is just because I still have monitors incomplete. The 2 misfire codes with the restricted performance looks to usually be ignition related (but may be fuel) based on my searches. At least I have a lead now, hopefully this is part of the same issue and not something else. I will keep searching, just wanted to update this thread.

 

I repeated the same test today but I was only able to get about 4 miles before I had to hit the brakes. No "restricted performance" but I did find some pending codes: p0301-p0307 and p1316 (also p1000).

To recap: Cruise control set at around 73MPH for about 5miles caused "restricted performance" p0300, p1316. When I repeated it for 4 miles I got no restricted performance or p0300, but I did get the p1316 and misfire codes for all 8 cylinders (p0301-p0308). The comprehensive component, cat and evap monitors all will not set and my fuel trims are still high.

The p1316 makes me nervous since I think it should mean a ton of raw fuel is dumping into the cats. I wish it would point me somewhere more specific, looks like all cylinders are impacted pretty equally based on the codes.

Any ideas? If a vacuum leak is causing all of this would this make sense as another symptom? (the tac is right around 2500rpm when I have cruise control set).

Also, I data logged most of the drive today, if there is anything anyone wants to see from that I can post it

 

It's like it's jumped timing or some such. To save going back a long thread it's not got any air leaks has it?