My 01 XKR seems a bit slower and quieter under hard acceleration. There are no codes.

I hooked up autoenginuity and under WOT acceleration on the road the MAP sensor indicates 13PSI, a little below the atmospheric 14.25 it indicates with the engine turned off. I have never looked at this before but I assume it should be around 20PSI. The intercoolers also seem quite a bit cooler to the touch than they usually are. They are usually hot after a long drive, they seem just to be warm now. This makes me think I am not getting boost.

When I rev the car in park the bypass valve moves, so it seems to be working, and the supercharger is making its typical growling noise.

Should the MAP sensor be over 14PSI under WOT? What if I hook up a vacuum-boost gauge, what should that read?

Any help would be appreciated.

I have looked in JTIS but that seems nearly useless for troubleshooting like this.

 

How old is your MAF sensor? I had some moments of poor performance despite not throwing any codes, and installing a new MAF sensor fixed that. My issues were in specific RPM bands (don't remember exactly, but somewhere around 3k RPM and up).

 

Perhaps worth checking IAT2 - if your car has it as mine does - since it is closely involved. If it changes from cold in a sane way then it's likely OK.

Also, check the fuel pressure as I suppose it also matters.

I think your SC pump must be OK or you'd have hot not cold ICs.

 

The 2001 XKR has two fuel pumps - if only one is working it would run, but not get full power at WOT. There is an easy way to check by pulling the fuses.

https://www.jaguarforums.com/forum/x...el-pump-85882/

 

Thanks for the advice. I will clean the MAF to start and check the IAT temps if I can find them on the A.E.

The fuel pumps are only about a year old, I changed both of them last year.

 

IAT2 will not be there on a standard OBD tool.

 

The autoenginuity does have IAT2 but it is in volts, they apparently don't have the transfer function programmed. It was a 90F day here. With the engine cold IAT2 was 1.85 volts. I started it and it stayed about the same initially, dropping a little bit to about 1.83 volts. I took it for a spireted 5 minute drive and it dropped to about 1.45 volts. I idled it for a while and turned it off for about 5 minutes. When I turned it back on it ideled at about 1.1 volts. I don't know if those values are reasonable or not, does anyone know how those values correspond to temp?.

IAT1 is logged in actual F degrees, cold it was 90F, which matched the wall thermometer in the garage. It rose to 105F driving and then was 122F idling after being shut off for a few minutes.

I logged the fuel pump relays and the fuel pump monitors. Fuel pump relay 1 was energized the entire time. Fuel pump relay 2 was not energized at all during my drive, including some WOT runs. Fuel pump monitor 1 and fuel pump monitor 2 were 0 the whole time. Does the aux fuel pump only turn on when needed?

Looking at the vacuum routing, MAP comes from upstream of the supercharger, so I was mistaken earlier and it makes sense it would not see any boost. I hooked up a vacuum-boost gauge by teeing into the fuel pressure regulator line. That seemed good, it showed high vacuum idling and when I flloored it while driving it went into boost immediately. The gauge only went to 10 PSI positive and it would peg at WOT.

 

Fuel pump 2 is not on all the time, ECU enables when needed. Seems a little strange you did not log it coming on under WOT. I would pull the fuse for #1 and see if the car starts - it will switch to using pump 2 if it recognises that pump 1 is dead, may take a few seconds. If no good, then pump 2 has an issue...
Seems you have good boost, so fuel seems the most likely suspect - pump, filter, pressure regulator etc. - you could also check fuel pressure if possible at high revs/load.

background on IAT2, this is my rough estimate on calibration, but seems you are good on boost since you are getting over 10 psi, should get 13-14 I think.
Temp (F) Volts
14 4.084
32 3.627
50 3.09
68 2.527
86 1.993
104 1.533
122 1.157
140 0.868
158 0.648
176 0.475
194 0.362
212 0.274
230 0.211
248 0.164

 

Building off the aux fuel pump possibility, if you can confirm it's not coming on with Chirpy's test, see if it comes on by jumping the relay terminals in the trunk relay box (more detailed instructions at https://www.jaguarforums.com/forum/x...el-pump-85882/ ); with luck it's just a bad relay rather than a bad pump entirely.

 

Thanks. I will check out the aux pump as described. The pumps are relatively new. They are delphi fuel pumps, not the el cheapos from China.

What info does the ECM use to command the aux pump on? Is it based on throttle position or MAF output or something else?

I am starting to wonder if it might be a clogged cat since the other syptom (quiter during WOT) might be caused by a clogged cat.

 

+1 I check both fuel pumps on a regular basis by jumping each fuel pump relay socket and listening to hear if the pump is running. (while engine is off)