1999 XK8 Convertible: Ok, so yesterday I decided to pass a driver on the freeway going 30 under the speed limit. I had to do it quickly so I punched it, forgetting that I was in sport mode. I inadvertently touched the red zone at 7,000 rpms for a second or two and it tripped the restricted performance and the engine stumbled like it was running out of gas, then ran fine when I let off.


I pull off the freeway, shut down, wait, restart, message board still says restricted performance. I warily finish driving to work, noticing no difference in driving.


After work I drive home, no difference. However, when I tried to accelerate quickly....it stumbled. I did a hard reset, but that didn't clear anything.


I can drive any speed providing I start out like I'm not driving a Jaguar, a.k.a, like a good boy. I don't have a code reader to read my codes so I'm stopping by the auto parts store to have them read them. Probably buy a reader too.


Prior to the codes being read, here are the clues after restricted performace:
1) Normal driving is fine, stumbles on rapid acceleration
2) Heater / AC display reads "ER" and beeps 10 times, then operates normally
3) My temperature gauge is suddenly not working


Any suggestions?

 

Get the codes read, and report them back here (along with your model year)....

 

Sounds like fuel starvation under load. When was your filter last changed?

 

Fuel filter? What's that? Just kidding, I've had it for three years and never changed it. Sounds like a good thing to do regardless, thank you for the reminder.

 

The clip that holds the connector on the Temp sensors breaks and when you accelerate rapidly, the temp sensor becomes unplugged. The plug is right on top of the manifold near the thermostat tower under the right side cover.

You get restricted performance and the temp gage goes to zero.

Happened multiple times to me, before I fixed it.

Went to junkyard, cut the pigtail with a unbroken connector off another Jag 4.0L and soldered it in. Problem solved.

 

Attached are pictures of the sensor location, the broken clip and a repaired clip.

It may be a long shot, but it what gave me these errors on my '97.

 

Ungn: Yep, that's what happened. My crossover pipe failed a few months ago as it was the original micarta (?) material. It went soft on the ends and when removing that very clip, the little tab popped off. (God bless the Jaguar procurement agents for selecting such fine, fine plastic materials...) After installing the new pipe, I reattached the connector and promptly forgot about it. Yesterday while getting a haircut I was thinking about the clues I typed in my original post and remembered that clip. when I left, I popped the hood and saw the connector completely unplugged. I then scorched my wrist on the thermostat tower, plugged the connector back in and turned the key. The restricted performance was gone and the temp gauge worked again! Today I'm going to use some tie wire to ensure the connector doesn't come off until I want it to.

KITTY IS ALIVE AGAIN!!!

 

My Kid actually found this for me. I drove my Miata to work one day so my 16 year old kid sees he Jag just sitting there... so he took it to high school. A few hours later I get a call that the he "thinks he broke the Jag".


I ask him what he did and he said he was "flooring it out of the parking lot". He checked the internet and though he needed "premium gas". I told him to park it and drive something else. When I got home, I noticed the Temp gage was Zero, so I figure I'd fix that first. Saw plug was loose, pushed it back on, all codes went away including restricted performance.


A few weeks later driving to work, I floored it to merge with traffic, I get "restricted performance" and temp gage goes to zero. Get to work, pop the hood and the sensor was unplugged again.


At that point I realized I had a process to generate restricted performance/temp gage zero.