Emissions MOT fail

[Davidqhog]

Well, my 1999 XJ8 Sovereign 4.0 failed its MOT on emissions. The engineer replaced a nearly new (5 months old) K&N filter but only a slight improvement. Today, they're trying a cat cleaner (presumably a liquid into the tank and then run it through).

I cleaned the MAF when I put in the K&N filter but I've read about there being 4 more sensors on this car (lamda sensors?) and they can be suspect at this age or contacts can be dodgy. But I haven't a clue where they are or what to look for. The garage seems to suspect the cats but they'd presumably cost more than the car is worth and if it's sensors that would be daft.

Anyone have any ideas what I can do?

Many thanks.

[ptjs1]

Davidqhog,

Before deciding what to change, it's important to understand on which aspect of emissions the car has failed. Have you been told what were the readings?

Paul

[J44EAG]

I agree fully with Paul.

The car must be fully diagnosed, any fault codes investigated, fueling trim and Lamda readings looked at. It will be a long and expensive haul if parts are just changed without a clear cut definition of where the fault may originate. Without that information, you will be shooting in the dark.

Mike K

[Brakebuster]

this could be as simple as a failed MAFF or a split in the induction pipe after the MAFF etc

don't give up yet if you can help it

BB

[J44EAG]

My experience in recent months leads to the following conclusions gained during extensive V8 maintenance and trouble shooting sessions.

Components downstream of the cylinder head particularly as regards leaking or rotten small vac or pressure pipes will usually cause lean mixture conditions. Lean Bank A&B PO171 and PO174 is often classic small pipe degradation.

MAF sensors usually have a long life but do tend to go "off" a little over the years. A dirty hot wire and bulb can be checked by removing two Torx screws on the unit immediately upstream of the air filter housing. The side of the bulb and hotwire pointing towards the air filter can become black with grim. Clean with spray carb cleaner as a first try.

Often a similar sensor known as the air inlet temperature sensor(IAT) can be found after the throttle body. It is similar to the MAF sensor. This can get gunked and may need cleaning. Ensure the slot or trench in which it fits is also clear of gunk.

Rich mixture issues are often down to blocked, failing or bad catalytic converters. As already said, Lamba sensors can fail over the years.

People often think fuel injectors will perform well for ever. That is not the case. They can be removed for cleaning professionally or by removing each one, separating from the fuel rail. Rigging a 9.6v PP3 battery to pulse the injector when out of the car and then rigging spray carb cleaner via step up pipes to an injector inlet. Pulsing the battery and spraying carb cleaner can restore a good spray pattern which atomizes the fuel correctly rather than have fuel horsed through the injector as a hose pipe action.

As an alternative to stripping injectors out, call in the local Terraclean man. He will be used to applying this excellent treatment direct to your car and it is quite amazing how such treatment clears out carbon and deposits from an engine which can cause very high emission issues. I`ve had the process done which has transformed my car at 83k miles. The treatment is designed to deal with high emissions problem cars. See the Wheeler Dealers XK8 episode where a high emissions car had its illegal emissions got back to sensible limits without dismantling in just twenty minutes. I have an article written which will appear in our magazine over the next couple of months. Believe me when I say the process is not far short of a total miracle solution for dirty cars. That statement is made from my own experience. Spending around £130 is small beer to pay to get a smelly car sorted. Have a look at this link.http://www.jec.org.uk/forums/viewtopic. ... 81&t=10766

In the meantime I would suggest a diagnosis with finding that would assist those here to help you towards getting the issue fixed. There is a cause and a reason for every problem. It just has to be found.

Hope that helps.

Mike K

[Davidqhog]

Hi everyone and thanks for such a fantastic response!

The car had been off the road for 2 months in a dry barn whilst I drove the Daimler for fun. The battery, old when I bought it 4 years ago, died in that time. I zapped it up and it started the car but a week later, dead. Swapped it for a new Yuasa 100ah and everything okay. But it had been 'down' for sometime.

Initial emission reading was 5% and the car had only been driven about 25 miles. After the cat cleaner, it was down to just over 3% but still a failure. My friendly engineer said running it would improve the level - so I went home the long way round on a dual carriageway at 70 mph - or thereabouts - for about 10 miles then on normal roads at normal speeds.

The 'front' lamda sensors were changed last year when I had a whole series of problems with plug coils - 8 new ones. I'm told there are no readouts on the garage's diagnostics. I've just bought my own diagnostic device so I can see what is or isn't going on.

Again, fantastic response from you guys. This Club is amazing and I wish I knew more about these wonderful machines. Sadly, I only know about software and hardware servers. But I'm learning and willing to learn - it's my job!

[ptjs1]

Davidqhog,

The 5% is the CO figure but what are the HC and lambda figures? You need to put the 3 figures into context before starting the diagnosis. Also, what type of machine has scanned the car? You need to be sure it's been scanned using software that can properly interpret the engine ecu.

Also, can your software monitor the lambda sensors voltage pattern so that we could understand if they are functioning properly.

As mentioned, I'd strongly suggest that you don't change anything or buy any new parts yet. This could still be a cheap, simple fix.

Cheers

Paul

[robv12]

a classic fail of an unused or lightly used car!!

I have an easy way of curing this, a hot run, the "Italian tune up", give a good old 30 miles blast, drove it like you stole it, then get it back to the MOT guy and get him to do the emissions first while the cats and lambdas are really hot and working well

always works for me

[Davidqhog]

Thanks again guys! All good replies.

I haven't tried my new diagnostic tool (Vgate Scan) yet so I'm going by what the mechanic told me on the 5% but I don't know what this applied to.

I'll try a few more high speed runs to see what happens and report back in due course. I have to say, even at 17 years old, the car still runs sweetly, quietly and comfortably. Once we're through the MOT, time to get the sagging roof liner fixed!

[Davidqhog]

Thought I'd give a final update. We have an MOT!

I was told the catalysts had probably melted and the ECU was faulty, this from a non-Jaguar mechanic. Since the cost of the cats & ECU would be worth more than the car, better look for a new car and scrap this one.

I live in Gloucestershire and a new Jaguar independent has recently opened in Swindon. I gave him a call and took the car over last Friday morning. That afternoon, he rang and said the O2 sensors ahead of the cats were U/S and had not been fitted properly (6 months ago). He couldn't tell whether the sensors after the cats were okay until he'd fitted new O2's.

To cut a long story short, the new sensors worked, the rear ones were okay and the MOT was passed.

Thanks to everyone on here and special thanks to Paul Titheradge of Wiltshire Jaguar http://www.wiltshirejaguar.co.uk/wiltsh ... r-swindon/. Lucky chap will now be getting all my Jaguar & Daimler business!

[ptjs1]

Davidqhog,

Great news! A proper simple diagnostic from someone who understands the cars is always the best approach. Monitoring lambda voltages is really key before jumping to conclusions about the cats. I'm not sure why he elt he couldn't assess the downstream ones before replacing the upstream ones but, hey, you've got the right result anyway! Well done!

Paul