Ok i just purchased a 2004 STR with 67,044 miles on her. She is in great condition for the most part. Just a couple small cosmetic things i need to address nothing major.

But i noticed every once and awhile when accelerate hard right at 3000rpm it will hesitate for a brief moment then kick back in hard. It does not do it all the time. No misfire codes or anything. Also it seems the gas mileage is a bit low compared to what i have read in a few post. I have filled tank twice and watched and driving around town i am hitting right at 63-68 miles from fuel to 3/4 tank, but that could be about right haven't owned her long enough to know.

I have been reading on the forum for the past 80 mins or so. Found some individuals having a similar issues with a few 2000-03 XJR and some just cleaned the MAF and it fixed the issues, someone said thier mechanic has seen the issue on the XJR a few times and it was the vacuum line from the supercharger to the fuel pump? not sure if the STR has the same setup.

Seen some people have fuel pump issues, but not with this same issues. From what i have read in some of tbe other cars pump #1 starts the car and 2 runs them, but if read correctly the STR at 3000 rpms both pumps feed the fuel system. Any help would be great.

Thanks for all your help in advance.

 

Read OBD codes and then watch fuel trims at idle & 2500rpm (parked, hot engine).

 

I scanned the car before i purchased it and no stored or pending codes. But i will look at the fuel trim data with my scanner.

Thanks for the replay.

 

Also i have put about 460 miles on it since i purchased it and 215 of them are highway miles 90 miles one way to work. So the ecu has had more then enough time/miles to cycle.

Ran her a bit hard also, about 130mph for about 5 miles and man she pull hard from 80 to 130 did it with ease and briskly . Also done 90-110 a few times just pushing her to see if i can push her to show any signs of issues. This is the only one i have noticed.

 

Here is the Long and Short term fuel trim real time at 2500rpms.

if would have went longer all the numbers would even out for the most part.


I also just pulled air filter and it is about the nasty filter i have seen i mean like clogged with like degree/mud. the MAF without doubt needs cleaning it black with degree particulars on it.

 

Ok ladies and gentlemen. After did the above video i cleaned the MAF and replaced the hideous air filter and while i was in there removed the WOT door flap.

Ok the car idles much smoother honestly a noticeable amount and push in the gas and it accelerates smooth also. Not sure if it fixed the hesitation issues as i acceleratored hard and at 3000rpms it just pulled smoother then it ever had since i owned it. But once again it doesn't do the hesitation issues all the time.

And seeing the air filter i think i will go ahead and do the spark plugs also. I know they are supposed to be good for 100K, but i just got her and want the peace of mind knowing they are good to go.

sorry for all the posts.

 

The STR uses 1 pump until 3000 rpm and then both run wide open. This is only on the STR. All the other S Types use the 2nd pump to keep the fuel level even (We have a dual sump gas tank) and the engine is run off of one pump all the time.

Have you changed the fuel filter?
Sounds like you have it fixed so probably just needed some basic maintenance.

I would at least look at the plugs but when I changed mine at 95K miles they were in great condition.

So your call on the plugs but I do recommend using the factory Iridium plugs.
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On my way to get a fuel filter now. pretty easy to change. looks it takes a 5/16 fuel tool to get lines off the filter.

 

It's a bit hidden too?
You know it's in the drivers side wheel well behind the wheel liner?
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yep i do.

 

Can't watch vids.

 

Great job and congrats! I've owned a STR and it was a complete joy to own and drive.