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MOT emission fail advice


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My 1998 110 300tdi failed it's MOT on emissions after having been sat off the road for about 6 months*. I had given it what I thought was a decent run to the test centre but apparently not and wondering if anyone can give me some advice about what to do. On the way back I drove it at 60mph in 3rd with the pedal to the floor for a few 0.5 mile stretches. I didn't see any black smoke pouring out the back and it's not smoky when it's running. Does that sound like I've given it a good enough blast or not? Is there anything else I can do to help get it through? The exhaust itself is in good condition with two new sections and it's had a change of oil and new oil/air/fuel filters.

* "Exhaust emissions exceed level of metered smoke for a turbo charged engine (8.2.2.2 (b))"

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Replace the fuel with fresh (drain the old first if you can), new fuel filter and make sure the air filter is clean and dry.  If that isn’t enough, you could try another garage; some are overzealous, some even create non-existent issues to generate repair work, which in this case could be as easy as leaving it in the front yard until later.  It could be that there are emissions that you are not seeing and they are being completely honest, but dodgy garages are nothing new.

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9 minutes ago, Stellaghost said:

As above, but also check out fuel additives that could assist cleaning piston and bores, rings could be stuck, unlikely but then nothing suprises me with landrover ownership regards Stephen

I was thinking along those lines too, but they could free up a lot of rubbish that would come out during the test.  Worth doing if you can run the vehicle around an burn that stuff off before the test and be on a regular tank. 

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Just my 2p but I would not go about doing all that just yet. What was the actual reading? Can you post up the emissions test results which should be printed on the back of the MOT fail sheet? 

 

It would be useful to know just how much it failed by. I have found with older more basic diesels that a dirty air filter is much more likely to cause this than old fuel. Different if it was a petrol. In addition the run you have given it will also have helped too.

 

*Edit, didn't notice that you had changed air filter already. Test results would still be useful 

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6 minutes ago, cackshifter said:

If it has been tweaked previously you could put it back nearer standard. Also check the pin in the fuel pump that bears against the boost pin isn't sticking.

or just wind the smoke screw in a turn for the MOT and wind it back out after....

 

To be honest the max smoke figure for a TDi is quite high so they do not normally fail unless smoke is present. I am guessing the fail will be marginal

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51 minutes ago, cackshifter said:

If it has been tweaked previously you could put it back nearer standard. Also check the pin in the fuel pump that bears against the boost pin isn't sticking.

^^^ do this plus give it a good service in terms of oil change and set of filters. If you want to go the extra mile get a set of new fuel injector nozzles for a belt and braces approach. 

Out of interest, does it have the EGR in place or has it been blanked off? 

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Thanks for everyone's help. They've been doing the MOT on the landy since I got it and seem pretty straight. I have the results but they're at home so I'll post up the figures when I get back from work. I have put new filters in but after the test so hopefully that will help too, I think the air filter that's in is nearly 2 years old. It's always looked clean when I've done the oil so I've just blown it out and refitted so it was probably due a new one. The EGR has been blanked off. 

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1 hour ago, landroversforever said:

Wonder how effective injector cleaner would be if its sat idling instead? 

Don't know, good question. My gut feeling is it wouldn't do much but that's just a guess as when I use it I go for a good old fashioned Italian tune up! 

If it were mine I'd be inclined to swap the injector nozzles for a new set if they haven't been done before. 

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I find a lot of the older diesels we fail have a soot build up in the exhaust, and it's that being blown out that causes the failure.

Also, later diesels have a manufactures limit sticker, this states the smoke figure the vehicle should be tested to, this will always be lower than the default figure if the sticker is missing...

A 300tdi has a plated limit of about 1.7, and that's what it should be tested to if the sticker is present.

If it were missing the default figure is 3.0... Just saying.

That said, my tweaked 200tdi sails through at around 1.4.

We are always very fair on our tests and try to get a pass. If we can see the figure is dropping over the six accelerations but not quite low enough, we'll repeat the test, If we're not too busy it'll get a blast up the village bypass and back to see if that sorts it.

I can tell fairly quickly if there's a fault with the engine or it just want a clear out.

1 hour ago, hurbie said:

there used to be injector cleaner that you can run your engine directly with (so no need to put it in the tank , just connect the feed in the bottle)

Most if not all will do this, on really dirty ones, we fill a new filter with injector cleaner, then run the engine at idle for 15 mins before giving it a blast.

To the OP, lets see the figures from the emissions print out.

 

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Thanks again for everyone's suggestions. I'm not sure if it's relevant but I recently changed the head gasket and as far as my untrained eye/ear can tell it's running pretty well for a 300tdi. It's got 178k on the clock.

The results are 3.64 - 3.93 - 4.45 - 0.85 - 2.18 - 1.7 (mean value 1.89).

It says "plate value - 1.68" on the vehicle details section

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1 hour ago, Snagger said:

Those results are all over the place, which suggests it isn’t being tested consistently.  That, or the fuel is inconsistent.  

I'd agree.

It's not wildly out though.

I'd stick some injector cleaner in a new filter, run it for 15 mins or so, then give it a good blast.

If you can arrange the re test so you arrive with it hot and cleared out that should pass.

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Thanks for everyone's help. I've ordered a bottle of RedX diesel system cleaner - sounds like wonder stuff! Is the consensus to put it into a new filter then, instead of straight into the tank? The diesel is probably about 8 months old and there's about half a tank, would it be worth draining it out and putting some fresh in or some premium diesel?

 

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27 minutes ago, Sharp said:

Thanks for everyone's help. I've ordered a bottle of RedX diesel system cleaner - sounds like wonder stuff! Is the consensus to put it into a new filter then, instead of straight into the tank? The diesel is probably about 8 months old and there's about half a tank, would it be worth draining it out and putting some fresh in or some premium diesel?

 

I'd be tempted to drain it and fill it with fresh diesel. Having a diesel tank half full can lead to moisture in the fuel which in turn can also lead to a black fungus growing in the diesel. 

Swap your fuel filter, pop in some neat cleaner and take it for an enthusiastic drive. 

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