Hi all,

I have an odd new problem with my otherwise fabulous XJR. Recently, the passenger side O2 sensor failed (typical, the one where you have to disassemble the entire car to get to it). I did drive with the EML light on for a while, which may have been a bit of a mistake; after a 200ish mile run up to Scotland last month, as I arrived at my destination the car stalled - it's never done that before.

Fortunately, when I left, it started right up & I drove home without incident. I did notice I was getting appalling MPG figures (16, when I'd expect nearer 22-23 on a run). I also noticed that when pulling up (at lights, junction, parking or whatever) the revs would drop perilously low - 2-300rpm or less. Occasionally, the car will then stall.

I've now had the O2 sensor replaced, and the EML light is off. But when I restarted the car after getting it home, it stalled 3 times in a row as I tried to leave my parking space. It restarted each time, but a bit hesitantly a couple of times (like it was cranking for longer than it should be, firing on some but not all cyls initially). I noticed that when I applied a small amount of throttle, the revs would drop right down (to stalling point); so on the 4th go I just put my foot on the brake & gave her a decent amount of throttle, which seemed to "work through" the bad spot. She didn't stall again on the (short) journey into town, but I didn't have to use the "just tickle the throttle" at any point, which may have been why.

My guess is one of 2 things: Either I've done some damage/blocked the nearside catalytic converter (if it's likely to be blocked, would a good hard blast down the motorway cure it?); or my throttle body is all gummed up with cr*p which is affecting the airflow at "just opened" throttle position? Another theory - gummed up injectors?

I'm going to throw some injector cleaner in her tonight & a fresh load of V-power fuel, what else should I be considering?

PS: When the car is cold, & "on choke", it doesn't stall (I occasionally get a "lump" when idling as it warms up, but it's always smooth as silk once fully warm).

Cheers!
Ade.

 

My XJR went through a phase of this, after having the fuel pumps fail. Then it settled down. My theory is that you can get some really nonsense adaptations going on in response to the bad running. You could clear the adaptations, or just keep driving.

 

Thanks Mark - good to know your Cat recovered... the joys of closed-loop self-tuning with a broken sensor.

It does sound like a good excuse for a blast up the motorway...

 

Do a hard reset so the ECU can re-adapt the other modules and throttle body. Just disconnect the neg. batt. cable from the neg. terminal and touch to the pos. for a few seconds.

 

Weirdly, my stalling problem is back.... but now under certain circumstances....

A couple of weeks back, I filled up with V-power as usual (1/2 tank), and drove for about 5 miles in steady city traffic. When I got where I was going, I noticed the "restricted performance" warning. Usual thing, "Running rich bank A" & "bank B". Normally this clears if I give it some beans, accept a bit of kangaooing, then everything is OK; but this time I just used my code reader to clear them. When I went to drive away, the car stalled... It did this about 4-5 times. Each time it restarted fine, albeit hesitantly a couple of times. After that - perfect..... until yesterday when I filled up again. Again, the car stalled as I left the petrol pump, and another 4-5 times after that, but once I'd managed to actually get it a few hundred yards up the road - perfectly smooth again.

So.... now I dread filling up... but I'm guessing this might be a fuel filter thing? i.e. when I fill up it disturbs some crap in my tank, which partially blocks the filter leading to low fuel pressure?

What is odd is, having started the car, if I leave it to idle it's fine; it's only when the revs are falling back to idle that it actually stalls...

Any ideas gratefully received. Apart from this issue, the car otherwise behaves impeccably, I can cheerfully drive 100s of miles without any trouble at all.

 

Look to fuel filter; might also check with an OBDII reader, if the temperature sensor is working. Also, clean the MAF sensor and check wiring.

 

Thanks for the reply. I spoke to my mechanic guy (I don't work on my day cars myself), he's going to check the fuel pump/filter/sender assembly. Might ask him to check the filler neck as well. I've tried the code reader - no new codes. Temp sensor (to the dash) is OK, is there a 2nd one for the ECU like on the old V12? MAF - will do, cheers.