My 1999 XK8 has failed its MOT on high emissions Co2 is 6% it should be less than 0.3% and Lambda is out of range.


It ticks over and runs very smoothly. Power seems fine but you can smell it's running rich.


There are no error codes other than P1111 which is correct and this has been confirmed by Jaguar Specialist he said it must be carboned up and needs a good run.


Looked at tberry6686 post of 24/12/2012 and gone through the various suggestions.

I have an ELM 327 Bluetooth code reader using Torque on my Android which shows the following.


Fuel Trim Bank1 long term 15.62%
Fuel Trim Bank1 Sensor 1 No Data
Fuel Trim Bank 1 Sensor 2 -10.16%
Fuel Trim Bank 1 short term 2.34% to -9.38%
Fuel Trim Bank 2 Long term 19.53%
Fuel trim Bank 2 Sensor 1 No data
Fuel trim Bank 2 Sensor 2 -10.16%
Fuel trim bank 2 Short term 25%
Mass airflow rate 4.09 to 15.22 g/sec tickover then engine revved
02 Volts bank 1 Sensor 1 No data
02 Volts bank 1 sensor 2 0 to 0.21V
02 Volts bank 2 Sensor 1 No data
02 Volts bank 2 sensor 2 0 to 0.27

The fuel trims seem way out on both banks.
Not sure why both upstream sensors are showing no data. They look fairly new.

I have cleaned the throttle body and MAFS but these looked clean anyway there was some gunge in the Part-Load breather. I have done a hard reset i.e. disconnected the battery gone through the re calibration. I have had it Terracleaned and this has improved the hydro carbons.


I have taken it for a long run and revved it quite hard but still no difference. I have ordered the code reader recommended by steveinfrance in the afore mentioned post just in case my code reader is telling lies.


Any ideas?

 

First thought was to have it terracleaned, but its made no difference. Have you checked the plugs? Their condition could give some clue, are they the same on each bank? Rich both sides? Just a thought......
ArtyH

 

Hi

My 1999 had the same problem passing its MOT 2 years ago. The solution was new O2 sensors. They should be considered as a time limited part.

regards

Smoggy

 

Warm engine, park, rev to about 2500 and watch LTFT per bank for 5-10 secs. If both are much nearer zero you likely have an air leak (between MAF and engine).

At about 20% you're close to where it would flag lean codes (P0171 & P0174) because it's having to add lots of fuel. It uses various sensors to figure out what's happening and then trims based largely on O2 sensors. Here's a guide OnBoardDiagnostics.com - Engine Basics

One snag is that adding so much fuel it may have been damaging the cats for quite some time. Hope not!

It's worthwhile to check the other sensors for plausibility (IAT, ECT etc). They're being relied upon unless it sees them as clearly faulty.

 

Thanks Jagv8 I'll do as you suggest I'm away for the weekend so won't be able to try until next week.
I'd be more comfortable if both sensor 1s were showing some data. I have a replacement obd2 reader on order. Could do with trying my obd 2 on a working v8 just to see if the sensors show some data. I've had the MAF out and cleaned it and checked all the plastic for leaks. Where else coukd there be an induction leak on both babks?

 

You don't want it (it'll be elsewhere - under another name - because they're wideband). What you DO want are trims and you have... oh, I'm guessing: idle ones only, so far.

 

I use an air/fuel ratio meter. These meters used to be very expensive, but recent costs are around $US 350. The meter should read 14.7:1 during closed loop mode steady state load/no load. The wide band 02 sensors keep it at this ratio making minor adjustments to this optimum (for emissions) fuel ratio. If your fuel ratios start to vary from 14.7 (closed loop) then the most likely cause is O2 sensors. 02 sensors do degrade and fail simply with age alone, and your sensors are past their age date.

 

$350 for that? No longer worth it. He can get AFR for about $15 and a lot more.

 

I've done as suggested and this was the result.


Tickover
LTFT1 19.5% STFT1 25%
LTFT2 19.5% STFT2 25%


Increased revs to 2500 rpm
LTFT1 16.4% STFT1 25%
LTFT2 18.8% STFT2 25%


Tried it again revs 2500
LTFT1 17.2% STFT1 25%
LTFT2 19.5% STFT2 25%


When went back to tickover bank 2 climbed back up to 25% slower than bank 1
IAT was 36c this was 13c when I first started the engine
MAF was 14.1 g at 2500 rpm


At a bit of a loss now I thought if it was an induction leak the LTFT would have gone lower than it this but I have no experience in this areas


Any ideas?

 

Horrors. Agreed - it does not look like an air leak.

You've had the car long enough that it was OK on emissions a year ago? And not had any non-standard emissions-related (including spark plugs) work?

Maybe a blocked fuel filter so it's struggling to get what it wants? Has it been changed recently?

Maybe a MAF gone bad? (They only sometimes clean.)

As both banks are similar you can concentrate on things common to both banks. (So, for example, I can't see how it could be 2 bad cats or 2 bad O2 sensor.)

 

Still struggling to resolve the problem. Rechecked all the induction pipes but couldn't find any leaks. Looked at the Maf through a magnifying glass and could see contamination on the wires. Re-cleaned and the stft dropped on both banks. Thought I'd fixed it. Reset the ecu but after time ltft and stft back to where they were. Fitted a new Maf but no different. If it was the fuel supply eg blocked filter etc wouldn't I be getting problems at high revs eg hesitating etc.

The 2 02 sensors look new. Is it possible the wrong ones have been fitted? They have 2 black wires a white and a blue if that means anything. Thinking the problem may have been Maf and previous owner changed the 02s. I have only had the car for 4 months. I can get a used 02 for £25 so I was thinking of getting one and seeing if it made a difference on one bank.

 

So you didn't have this vehicle when it passed the MoT last year.

You could be troubleshooting an issue the PO has failed to rectify. Incorrect HO2 sensors or mixed up harness connections are a possibility.

Graham

 

Maybe the detailed actual emissions values may help. BTW, you don't mean CO2

Also useful would be old readings but I'm guessing you don't have them.

 

My XK8, which wasn't running too smoothly, just failed the test in France for high emissions with no dash warnings. I tried a cleaner, changed the air filter and plugs (oil in 3 tubes so I'll have to do the cam cover gaskets soon) and none of this worked. The Jaguar garage helpfully recommended a Bosch garage near Toulon, and they found P1646 & P1647 faults, which correspond to both pre-cat CO sensors. They changed these (190Euros + tax & 2.5 hours labour) and, fingers crossed, I have a pass certificate and happy puuuurrrring Cat back.
I hope this info helps some one.

Best regards
John

 

Not updated this thread since Jan.
In January checked wiring to upstream o2 sensor and everything as expected. Disconnected A bank 02 sensor and P0141 error displayed nothing else, car remained in open loop. Due to other commitments decided to take the car to my local Independent Jaguar Specialist (so called)


They changed the MAF which I had already done. They kept it until March then contacted me to say all was now ok, they had changed the fuel injectors as they were leaking. My o2 reader still showed LTFT at 19.5% on both banks. Had the MOT garage put it on their gas analyser and it was no different.


Took it back to the Jag specialist. They kept it until August waiting for a ECU to become available. They installed this but this did not cure the problem. Reinstalled the original. This must be a record, a car in a Jag specialist for 9 months and not fixed.


Spoke to the guy at the Jag specialist and started discussing the fuel trims with him. He stated that nobody undertstood fuel trims at which point I lost all confidence in him.


I now have the car back (October). I have been too busy over the summer to chase the garage and have had no time to devote to the car.


When I return from holiday in November my plan is.


Inject propane into the air intake, if the 02 sensors are working I expect the STFT to go minus. If not then o2 sensors are not working. Have seen this on a uTube video.
Change the upstream o2 sensors which I have suspected all along. Just seems odd that both sensors are faulty and that they look fairly new?


The car runs really smoothly, but only getting about 16 mpg.


I'll keep the forum updated on progress.

 

Sorry to hear this take so long, which is odd, as a good mechanic should be able to fix this quickly.

1st of all you need to establish if the maf flow is as expected, so let the engine idle, and after the engine reaches operating temperature, check the maf flow, and report it back here. I am not sure what the default values are, but many have posted this already.

That way you will know if the ECU is working with the correct values, if it’s not, that at least you know where to look for (ie maf cabling air leaks etc).

A next simple test would be to check the fuel pressure, if that’s not ok, you again know in which areas you need to look for.


Edit:
Only see it now, if the above 4.09 gr/sec was at idle, than that is already wrong, iirc it should be just above 5 or so. Please check again this value, as then you will know where to search for 1st.
Nevertheless checking fuel pressure for just in case would be good as well.

 

Thanks for the post. Getting ready to go on holiday today but managed to get a few minutes to plug in the obd2 reader and bring the car upto normal temperature. This is the first time since it has been returned from the Jag specialist. Things have changed.

LTFT1 19.5% STFT1 10%
LTFT2 3.9% STFT2 0%

Not seen this before, so it looks like whatever they have done has fixed Bank 2.

Noticed though that intermittently staying in "open loop engine decelerating" after engine has been revved and took a while to go into closed loop. Again not seen this before previously jumped straight into closed loop after being revved.

As requested MAF is 4,9% at idle rises to 17% at 2500 ram.

Going on holiday tomorrow for 3 weeks so won't be able to do anymore analysis until November. However it looks promising and I will start looking at Bank 1 when I come back.

 

Started looking at the problem again end of November.

Ltft 19.5%
Stft1 18%
Ltft 2 3.7%
Stft1 0%

Injected propane into air cleaner

Bank 1 stayed the same
Ltft2 3.7%r
Stft2 dropped to_2%

Concluded Bank 1 upstream sensor was faulty. Removed it and took it to Jaguar Spares in Bolton. They tested it and said my sensor was OK and from what I told them they reckoned the cat on Bank 1 was faulty. Wasn't convinced as they only measured the resistance of the heater.

Gave up at this point and took it to Mike Horner Jag specialist.

He changed the cat on Bank 1 and emissions fixed. Passed MOT.

The fuel trims are now


Ltft1- 7%
Stft1 0%
Ltft2 - 7%
Stft 0%

What a saga but now fixed. Mpg improved from 16 to 26.