I hate for my first post to be a support one, but as my girlfriend says "if I don't talk about issues they just get worse".
I have a 2001 XJ V8 Sport and all was well for the first week of ownership. She even did a 250 mile round trip with no issues right after I purchased her. Sunday however my check engine light came on and the dreaded Restricted Performance message came up on the display with an amber indicator.
Thats when it went pair shapped. The car would act like it was loosing power under anything but a soft touch on the throttle. And under gentle acceleration from pull away she would lurch forward as if I had pushed hard on the throttle. At this time I was about 50miles from home and the message would clear for a few seconds, but would return just as quickly and was on for 99% of the jourrney home.
I did get her home and the next day was going to take her to my Indie guy, but apparently he went on holiday (I never got the memo). The Restricted performance message was there at startup and remained all day. So I did some reading on the forum and wondered if this might be related to the throttle body fault which kept popping up under these symptoms.
I found a how to on cleaning the throttle body, Maf and the part load breather orifice. I was able to clean all but the Maf completely since one of the retaining screws had rounded off. I still gave it a good soaking insitue with non residue electrical contact cleaner, but this obviously is not a thorough cleaning.
The throttle body and linkage was pretty clean and I could find no cracks in the inlet pipe. She already had a new air filter which was fine.
After doing the above I took her for a 15 mile run. There was no error message (although the check engine light remained, but I assume it will stay till the fault code is cleared). She laboured under heavy acceleration once and the message reappeared, but it cleared after backing off from the throttle and hasn't reappeared yet even with a heavy foot.
I'm still not sure that I have solved this issue, and would have liked to have reset the computer. but since I don't have the radio code I felt that would have to wait.
Is there anything else that I could clean/inspect whilst I wait for my indie to return? At which point I will get the fault codes if any.

Many thanks in advance. Steve.

 

Hi Steve, and welcome. Your girlfriend is wrong, the more you talk about it the worse the issues get (relationship issues I mean !). But I digress. Everybody on here is going to tell you to go out and get an OBDII code reader so you can read your own codes and reset them. They are cheap now and easy to use and vital to troubleshooting. You do need one to reset the "P" codes but you only need the radio codes for the radio. (unrelated). I've had restricted performance once or twice (everybody has). For me, it was a vacuum leak at the part-load breather hose. So, look around the archives (search function), and get yourself a code reader.

 

Thanks, I appreciate the response, and will get a reader.

Steve

 

Okay I have ordered a OBDII code reader, shocked they are so cheap. I got a bluetooth one so I can play like the Fast and the Furious with a laptop in the car

 

It's been a long wait for the OBD scanner, with the Restricted mode becomeing a permant fixture most of the time. Although forcing (if thats the right way to describe it) the engine over 3000 rpm would remove the warning for a limited time. Today was the worst of it with the car running very rough from start whilst I ran errands. Which continued with every start.
However the scanner arived today and after trying several Bluetooth devices and programs finally found a match that would connect with the scanner.

Scanmaster ELM running on my Win8 64bit tablet

The software has far more functions than I will ever use, and took a little getting used to but I did manage to pull the codes on a very rough running engine.



Pretty self explanitory I think except for the P1000 code. So I cleared the codes and reset the check engine light. (such a good feeling to get rid of that yourself), shut the car down for about 15 mins. then restarted her. No check engine light, no rough idle, and now the throttle was far smoother. So I took her for a 10mile run. Everything seemed right untill about 90mph and she would become hesitant and would feel like she was miss firing.
Anyway no check engine light and no Restricted mode. Got home and reran the scan tool.



Again no suprises, and I guess the lean mixture could I assume cause the hesitation at high revs?

I have been reading about the P0171/174 codes, I guess this is not going to just be a trip to the shop for a mixture adjust. .

 

Maybe simpler. A bottle of Gumout's Best in gas tank used to solve these codes on my Range Rover qnd Land Rover. good for about 3000miles.

And I agree with Jim Legge, talking about it is akin to keep digging when you are in a hole . . .

 

Will see if I can find a British equivalent, will look over the induction side again as well looking for leaks and get the MAF out for a proper cleaning with a non residue contact cleaner.

 

Stopped in at the local Jag dealer today and politely asked for the radio code, which the young lady behind the counter furnished for me (suprisingly at no charge). So after I did a through check of the air induction side of things, along with a proper cleaning of the MAF. I was able to nervously do a power cycle on the car. Thankfully the radio had never been changed and the codes worked without issue.

The car is running far stronger now, but I can feel that it is not quite right yet. This may be some more driving time is needed since I power cycled, although not completely sure on that.

I still have the P1000 code but from what I have read this should clear on its own.

 

I would go looking harder for an air leak.

 

I do have concerns that the leak is actually at the throttle body seal, and that a new rubber seal is needed. There is no damage to the old one but it is very pliable and it is possible that air is being dragged in there. Can I get the various O rings for the ancillary breather pipes as well?


Steve

 

There are several places that air may be leaking to cause problems.
The trunk from the air cleaner to throttle body (TB), remove it completely, flex it gently to see if there are any cracks, especially along bottom. While there, check the resonator, ( blanked tube about 4" long sticking out of side of trunk). These are known to crack at the joint with the trunk.
I think you mentioned the seal between trunk and throttle body.
Check o rings on full load breather, between trunk and cam cover, drivers side.
Check part load breather tube, small one , passenger side, runs from cam cover, under inlet manifold, to TB. It suffers a lot from temperature.
There are some vacuum hoses which run from TB to a module on the baulkhead, which are part of the fuel system vapour recovery system.
If that doesn't fix it, somebody may have disturbed the inlet manifold and re-used the old seals.

 

Thank you Fredd60. I have to be away for the next week, but will go over everything you mentioned again. Along with the other hoses from the throttle body.


Steve

 

If you are not running lean at low speeds, but running lean at high speeds, that is a fuel delivery problem. That is because a vacuum leak is masked at high speed since it forms a smaller part of the total air delivery.

The two major causes are a clogged fuel filter and a fuel pump on the way out. The fuel filter is relatively easy ... the fuel pump not so much. Fuel pressure can be confirmed at the schrader valve on the fuel rail.

 

Thanks for the extra info. I think at the very least I should also look at the fuel filter anyway. Throttle response at low revs can be a tad snatchy (is that a word) which could be relative to either issue you have pointed out. Unfortunately it will be a week now before I can address this any further.


Steve

 

I haven't had any time to pursue this fault due to having a parent on both sides of the family in hospital at this time. I have however now done over 3k miles on the XJ. Hopefully I will be able to spend more time out of the car and resolve this issue, which now seems only to occur after starting the car and last for perhaps no more than a minute or two. After that it does not happen again regardless of driving distance.

 

ohhhhhhhh....diddo on that gum out.....its a miricle worker....so glad of your results....with the reader/scanner.....went through what you went through along time ago with my 85 xj6...what a car......i eventually was unable to get the car to move forward in drive..(but worked in reverse)....thought the trans had gone.........it was a throttle body/linkage issue......good luck....

 

Another possibility is lazy O2 sensors, although your symptoms seem more dramatic than I'd expect from that.
Should you find that you do need a throttle body I can oblige you with a good used one I purchased during a particularly frustrating diagnostic bout of my own.
Cheap as chips if it'll help.