My 99 XK8(65000m) keeps flagging restricted performance on intermittantly running rich, both banks. Doesn't run rich all the time, just for a moment - enough to flag up.My repair shop has changed the MAF ,made no difference,checked it again and say they cannot figure what is wrong - first one ever to beat them,apparently.Anybody had this or has any ideas as to the cause??

 

Did your shop pull codes? If the fault is intermittent, you may need to drive with the scanner plugged in until it happens and check it then.

 

Yes they drove it with the diagnostic plugged in - the fuel trims just suddenly go rich, then back to normal ranges.Checked fuel pressures, evap valve,you name it, they did it. They say they've never had one do this fault before. Sometimes I can drive it and it doesn't happen other times it'll do it twice three times in a day.Before they changed the MAF they said it was running lean- and yes, they downloaded new software into the car.

 

A intermittent connection to the MAF or Throttle Position Sensor could cause a change the Fuel Trims on both Banks.

This could be a bad connection anywhere in the Harness Connectors or at the ECM.

Or a bad ECM itself.

 

I've decided to get myself a scanner to keep a closer eye on this - any recommendations from members? Would I be better going for something like Autoenguinuity for my laptop?(presumably with the Jaguar add on)

 

+1

All the above and another possibility: bad Engine Coolant Temperature sensor sending inconsistent signal to ECM - interpreted as cold engine and mixture being adjusted to suit.

Graham

 

Thanks Graham that answered my question, finished changing the thermostat tower and the low coolant message was still on. Driving around today and set 4 different miss fire codes. Erased all the codes and the car is running like a top. Have ordered the low coolant sensor. Thanks Jim

 

Jim,

It's the ECT (Engine Coolant Temperature) sensor I suggested may be at fault. See item 2 on page 2:

XK8 1999 - Electronic Engine Controls.pdf

The coolant level sensor in the expansion tank triggers the amber low coolant warning light on the dash but isn't part of the engine management system.

Graham

 

Thanks Graham, I think this is the cheapest part yet and the easiest to change. $18.50 Jim

 

I am having the same issue with my 99XK8. intermittent low coolant and restricted performance . Where did you get the new coolant sensor? thanks Jeff

 

LOOOOOK WHAT I FOUND

Parts Bin - Auto Parts and Accessories Catalog - engine coolant temperature sensor - 2000 Jaguar Vanden Plas

I'll be purchasing one of these things myself! Thanks for the advice everybody.

 

OK, I'll chime in on this one. When I had a small breach in a head gasket (no steamy exhaust or milk in mt oil pan), it would trickle very slightly into the cylinder after driving and then parking with pressure on the system. The following cold start would yield a misfire for about a minute and then clean up. I had an intermittent low coolant message but the car never overheated, and I kept filling the top tank maybe once a day. Mind you, I never realized it was a head gasket, i just thought it was a leaky from one of the heater tubes. The night I was going to tear into my heater core I was on the way to the shop and I was rolling at maybe 15 mph when I decided check out my passing gear and just put my foot to the floor. The trans downshifted and the engine hit about 3500 rpm and BAM! Power shutdown completely on/off about 5 times in rapid succession throwing me violently forward and back into the seat before I could get my foot off throttle. When I finally got out of it the car was still running but it was pissed! She gave me the "Restricted Performance" finger shaking and I continued the two blocks to the shop in Limp Home Mode. Since making repairs I have no more messages. I figured that maybe the computer sensed there was coolant in one of it's cylinders and protected itself from a catastrophic hydro. I would sure like to get some thoughts on that on/off reaction...

Thanks
Bill

 

bought it from the deale,r Advance was a few dollars high and had to order it.