For a while on rare occaisions I would get the dreaded restricted performance light and resulting 3000 rpm choke but it started getting worse. We went through all the "usual" including checking TB connections. The engine code read running rich.
The mechanic (another older Jag owner and well versed), after "adjusting a couple things" without success determined the Fuel Pressure regulator was not so good and Air Flow Meter was a "maybe".
Changed them both and then when scoping the engine declared all was as it should be. It did run smoother.
But, within a couple hours on came restricted performance and engine light again. Restricted, as usual, went away after a few minutes. It is now repeating more often. I also got since then brief, and so far once each, messages that coolant was low and engine oil was low. Neither are. He's thinking it's time to pull the control module and check it for possible bad capacitor or something.
Anyone with thoughts on this is encouraged to chime in. Clearly I want it fixed, but at the same time I don't want to spend umpteen trips to Mr. Wrench chasing ghosts.

 

While you were checking the simple things, did you check your battery? Low voltage causes many electrical gremlins in these cats.

 

Could easily be a coil pack also. If one has issues, the cylinder can misfire and lead to a rich condition also. It took me quite a while of chasing this issue with mine before it got bad enough it through a coil pack code. Does it at least identify a bank that is running rich? They aren't too difficult to get to, so if you have patience, you could buy a new one and play musical chairs until you find a bad one.

 

But first have the battery load tested by a local parts supplier like Autozone, etc.

 

Well he said he did but I'll follow up with a personal check.

 

On my last visit I was right near his shop when the restricted message came on so I zipped over right away. He stopped what he was doing and first put in the code reader which gave the same running rich code with no further info. He then put his full diagnostic scope on it and went through the whole thing. All was as it should be! Engine was running perfect.
So then he looks at me and says: "I want you to try something" and told me to pour a container of Chevron Techtron fuel treatment in it. He then said: "This could be the cheapest repair you ever make to this car" and proceeded to explain that it works as a cleanser through the entire system wherever fuel goes including right through the emissions system. I did. Within 2 days I got no more messages and have now been message free for over a week.



Through all of this he only charged me when he really did work on the car (no "analysis fee") and I know he put in more than he did charge. No bill at all for the last visit although he probably spent 45 minutes to an hour going throught the scope multiple times at various RPM's to try to get a problem reading.

Therefore, I would say I have found a good honest mechanic who knows his stuff in my area. For anyone interested it is:

D&R Auto
3025 N Old Dixie Highway
Delray Beach 33483
561-752-2233

Bob Earnest runs the place and I would say he is aptly named!

 

The very knowledgable mechanic who was going to 'Terraclean' my XK8 but whilst doing the pre- clean emission test declared it running super clean and didn't need to Terraclean it - sold me an Industry only fuel cleaner to stick in the petrol (u say gas) tank next time i filled her up with petrol - but as my car runs on LPG i've only filled her up to just under half so far - i really think the LPG has my car running super clean and i don't worry about MPG either as it's so much cheaper than petrol. This Restricted Performance as soon as the car's not charged enough is a pain in the butt.

 

these cars are VERY SENSITIVE to things. My thoughts would be, to replace your battery as well.Make sure the terminals are clean and mega fuse by battery corrosion free,

 

Now that it's been a while I thought I would update FTHOI.

Within a few miles of fueling up after the first Techtron enhanced tank I got another restricted performance and check engine light. I had another 20 OZ bottle of Techtron since they were 2 for one when I bought it and poured it in. Restricted performance light went out very quickly and didn't return. Check Engine light went out after a couple days. Note I only drove it around 15 miles daily commuting back and forth to work those days.
The next tank I absent-mindedly hit regular and didn't notice until the tank was 2/3-3/4 full. I stopped the pump and restarted with High Octane. After leaving the station the restricted performance light came on within a couple miles but no check engine. It went out a couple miles later and hasn't been seen since. I figure the last couple miles mixed the Hi-test in with the regular enough to raise the octane level enough to play nice and gave me a break! All good since then. No lights! I'm a happy camper on this one.

Did have another issue since then but it's totally different so will start another thread.

 

Hey Bleeth, could you please show me the bottle for this tech tron bottle, i facing the light of restricted performance each trip it comes and goes, and once its there, it reacts crazy each time RPM reaches 3,

regards
Moayad

 

Misnamed it slightly! It is Chevron Techron and available at pretty much all auto parts stores.

Restricted Performance message is actually a built in warning that due to some condition the on-board computer has decided to protect your engine by not allowing it to rev too high. That's why when it is lit your engine runs "crazy" around 3000 RPM's

In my case the check engine light would also come on sometimes and when checked on the reader indicated engine running rich on one side. Mechanic put his full diagnostic on it and determined that it wasn't, so he thought it just might be a little dirt buildup somewhere in the fuel system. The Techron basically acted as a cleaner.

 

+1 on that stuff. I put some in before my 320 mile trip last week. Was having random rough idle and now it idles so smooth you can hardly tell its running.

Dave