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I have a Jaguar XJ8/XJR year 2001. (code x308) in England, UK.
I purchased the car when it was 2 years old with only 8000 miles.
In the early years I had occasional problems with “Too Rich” codes. P0172 P0175
I believe it’s a problem from new!
Filling the fuel tank right up seamed to trigger the problem.
I could also tell the ECU engine light would come on soon, as the gearbox would hold to a gear too long before changing up. (around 30MPH) (this fact did amuse Jag-HQ somewhat!)
Under the Jaguar warranty I got the main dealer to look at it and was also in contact with Jaguar HQ.
They replaced the fuel pressure regulator. (I have the old one). They replaced the Air Meter.
They said the fuel trim was running off the end. They also reset it when they had it and that was probably making the fault go away more than replacing parts!
They got so desperate at one stage Jag HQ said they would replace the engine for me! But when I realised it would be a recon engine I said no (as mine had only 8K miles!). In any case the ancillaries would have been mine and the fault would have probably sill been present.
It wasn’t going to fix itself so in desperation I fitted a new evap purge valve. (old one seamed ok)
The years past, it was well out of warranty, the fault lay dormant and I learnt to live with it somehow. Probably disconnecting the battery to reset the ECU, and in more recent years only filling the fuel tank to half way. (and ensuring the fuel was mostly used up before adding more)
I measured the fuel pressure recently and it seemed within spec.
I have had the car conk out on me a few times when trying to pull away. It doesn’t like hot weather. It doesn’t like being stuck in traffic idling. It doesn’t like refuelling. You will be unsurprised to know the MPG isn’t great (but how would I know anyway!)
Once I have had to remove the spark plugs and clean all the back soot of them to get the car running again!
In recent years I learnt, briefly disconnecting the Air meter with the ignition on would reset something, and make it idle lovely again (rather than pink). I thought it was resetting the fuel trim to mid, but now I am unsure.
Having purchased 3 fault code readers in the past and them not working on this car, last year I finally managed to get some that work. (one being a WiFi one giving live readings). I thought at last I may be able to sort this, but I am a bit stumped. So far I have noticed the TPS throttle position never goes to 0%. Normally 3%. Sadly a simple cable adjustment hasn’t helped!
The fuel trims seam to be around -10% to -20%
Pending rich codes. And today the light came on.As the car gets old, this appears to be a more frequent issue. Would love to solve now!
Any advice on what I should do next to find the problem?
Could it really be the TPS? The jag fault code chart does suggest TPS a possibility.
The only thing I can think of is to disconnect the oxygen sensors and run open loop, but I don’t want to damage the cats
These UK cars evap systems are not as sophisticated as the US requirements. We don’t have a tank pressure sensor, and we don’t have a valve to close the canister to atmosphere. The end of the evap is open to air.
On my year car they fitted an extra canister in series (like US spec). But they deleted the Rochester valve that earlier cars had in the evap line from the tank.
I have watched an evap diagnostic video, however the UK system is more basic.Advise on what to look for next much appreciated.
Have also had code P1647 pending twice.
Diagrams of evap system.
What is fitted to mine is a hybrid of both of them!
2 canisters and no one way valve.
no electric valve by canister.UK evap system
USA evap system
Having watched more videos
The fuel trims seam to be around -10% to -20% AT IDLE.
Don’t think my oxygen is cycling 0.1 – 0.9 at idle. Maybe as TPS isn’t at 0%?Good luck with your new job. I know it is key.
Note to self.
I squeezed the eval pipe but the engine note did not change.
I activated the evap solenoid with 12v and the engine stalled. I repeated this twice.Evap solenoid is good to me.
What else can cause rich condition?
Sooted up oxygen sensor?
So I replaced an oxygen aenaor. Didn’t seam to improve it.
I have temporarily blanked the EGR and it’s much happier.
Fuel trims now about 2%
Only issue is the ECU knows I have blanked it and thrown p0400
when the weather got cooler in September, and I had a small hole in the EGR blank, the fuel trims were quickly going negative.
replied on the 4 02 sensors post… do the fuel pressure test first and verify no system leak down and correct pressure. we will get to that EGR as it sounds suspicious. you can have both problems or one leads to the other. both can give you the rich condition. if you work on both problems at the same time you will not know where the problem was and your fix could be temporary.
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