Ive had my 03 xjr for a few years...blew the engine and replaced it a few years back.

I Noticed my acceleration has been acting weird lately...sometimes it has plenty of power and doesn't miss a beat going up the rpms ...

but sometimes it will start off pulling nice then literally stop pulling ( just to give you an idea I will literally feel my body going forward from the deceleration )

this usually happens around 3000 rpm and will last until 4000 rpm ....at which point the acceleration will start again and I sink back into my seat when the acceleration starts again.

Sometimes i'll press the accelerator and feel major hesitation ...soo much that I just stop trying to accelerate.

It doesn't seem to do it at night when its cool outside ...

Also, The supercharger is very Hot when I touch it...isn't it supposed to be intercooled ?

The car has 130 000 miles

engine has about 90 000 miles

How do your xjr 's accelerate ? Smooth power all the way through the rpm range ?

 

It sounds like a fuel pump giving up. The car is equipped with 2, one comes in at boost @3000rpm.
Partial blocked fuel filter? consider this a service item with those miles.

How hot is hot? does the temp gauge ever go into the red?

Any check engine lights? Have you an obd reader?

 

If it were me, I'd check both fuel pumps by pulling the relays, and putting a jumper wire across terminals 30 and 87. You should hear the pump run.
Do this one at a time with the car turned off.

If that's ok I'd check the intercooler water pump (same thing with the jumper), and I'd go though the water level checking process, making sure there's no air trapped in the intercoolers.

Here's the fuel pump relays-

 

Well it only seems to do this at wide open throttle...so fuel pumps may be a good start. how big of a job is it $ wise ( hours and parts)


no codes and yes I do have the obd reader...

as for the supercharger temp, remember I recently had the issue of my circuit 14 blowing and fans not working ... when I touch the supercharger itself its really hot soo much I immediately take my hand off and couldn't leave it there. The two square boxes beside it ( sorry don't know what they are called ) are cooler but still hot. I can touch those and leave my hand there.

also , are both fans supposed to work at the same time ? havnt seen the bottom one working for a while , top one comes tho.

 

Going by memory, one fan runs, and at a certain temperature, they both run. You'll need to research that.
When you turn the ignition on, can you hear the intercooler pump run?

When you jumper the fuel pumps, do they both work?

 

You could be easily having more than one problem.

The air intake/ supercharger system has water jackets - you can see all of the hoses. If the engine is running hot ...both the engine and the water around all the components will be hot. You don't want these engines running hot.

The pumps are a known problem -- one that really should not happen ,,, sort of like the tensioners. So far I have been lucky

 

I also have this problem, started happening yesterday and came on here to write a post until I saw this thread.

Sure enough with foot hard down 100% throttle the car misses and splutters through the rev range and power feels generally down.

I also have suffered high feul trims for a while now and believe this could also be down to a faulty feul pump if any-one can confirm.

 

Go back to post#3 by atv007 and test the fuel pumps. When was the fuel filter last changed?

 

guys ...if it were one or both of the fuel pumps, shouldn't it throw a code at me when the car hesitates ?

 

Most of posts involving fuel pump failure do not refer to codes.

 

from experience, it may not throw a code, but it should display restricted performance on the dash

the ecm monitors the relays and can detect a relay failure, but not the pump itself

best thing is to jumper at the relay contacts in the fusebox and listen

 

well it gotten really bad now ...like major hesitation ...couldn't get to 60 mph in 18 seconds...

taking it to the shop here in Toronto ...will report back on what the issue is...

wish me luck

 

Mines in the garage right now, will update, theyve been looking for the problem for two days so far.....

 

what kind of fuel do you use ?

I used to only use shell v-power...but recently started filling up at other stations...

im wondering if this could be the cause ...

let me know how it works out for ya

 

Ive only ever used 95-Ron in mine, never had an issue.

Just picked her up from the garage they spent a total of 5 hours looking and couldn’t find a thing wrong. No air leaks etc etc.

They said the high fuel trims are likely to be like this due to my 200 cell sports cats, can any-one confirm this can happen? And there's a possibility my second fuel pump might on its way out.

They advised me to do a dyno to see if I'm loosing fuel pressure.

So I took her for a little ride and just spent the last 20 mins accelerating from 50-150mph and it hasn’t hesitated once. What’s is going on here!!

Could it have been some dirt in the fuel filter or something, if the pumpwas dying it wouldn’t work one minute and not the next?

Jameson they told me if the problem gets worse it's most likely my fuel filter, sounds like this could be your problem, they have quoted me 4 hours to removed and replace the filter.

 

Picking my xjr up today from my mechanic with 2 new pumps and pick up filters. A shade under $900.

 

they quoted 4 hours to replace the fuel filter?

 

Sorry my mistake I ment pump

 

yes, that's what my guy said too... 4 hours to replace both pumps and 180$ per pump which is crazy...say some on ebay for less than half of that.

at 130 000k miles im wondering if they are due soon anyways... ?

The intermittent nature of the problem makes me hope/Think it might only be the fuel filter... If the pumps would fail I would assume they would fail and just stop working.

The problem started a while back and slowly got worse over time....

im wondering if I should just change the fuel filter and see what happens...?

 

The SC is expected to be hot! It's all a question of how hot. On boost loads of heat is created and the intercoolers only get rid of so much. Even then the SC will be hot.

If people would post their SC temperatures that would help others. (I don't have the car so can't.)

On my car, and likely the one(s) here, there's a second IAT (IAT2) that lets the PCM see how hot the mixture is after the intercoolers and it's IAT2 that can make it pull timing / go restricted performance if too hot.

Fuel trims are easily read with an OBD tool with live data. DIY - easy and cheap. Check at idle & about 2500rpm, parked, engine hot. You LTFTs want near zero, say within 10 of it.