MOT Fail

[liam.wtf]

****** thing failed its MOT... On emissions of all things!
They used the plate value (which is stupidly low, thanks Audi!), but would have failed if using the default value of 3... only just!

Any idea what I can do to get this number down for a retest? Garage used some 44k fuel additive but will have to wait and see! I've seen people suggest a EGR clean which is a bit of an ****. But also going full whack down the road (will do this later after a tank of fuel).
Any ideas will be appreciated!

 

[pauldazzle]

Coolant temp sensor would be one of my first suspects. It's notorious for failing on VW/Audi cars from that era, & can cuase the ECU to overfuel, which in turn messes up emissions. It's easy to test if you have access to VCDS/Vagcom.
EGR is also a very common issue as it's prone to clogging up, easy to remove & clean though.

 

[liam.wtf]

Coolant temp sensor would be one of my first suspects. It's notorious for failing on VW/Audi cars from that era, & can cuase the ECU to overfuel, which in turn messes up emissions. It's easy to test if you have access to VCDS/Vagcom.
EGR is also a very common issue as it's prone to clogging up, easy to remove & clean though.

Hi mate, cheers for the response. Funnily enough I changed the coolant temp sensor earlier in the year as it wouldn’t start in the cold (it thought the temp was at 90 even after sitting in -8 weather all night!) I have the full Version of VCDS lite, how would I got about doing a test? I was also thinking of doing the EGR as I saw that may be causing it. Fun project for a dark Friday night hahah!

 

[pauldazzle]

Temp will be in the engine module measuring blocks in VCDS. EGR is easy to remove, just 3 torx bolts, & unclip the pipes. Carb or brake cleaner a stiff toothbrush, an implement to scrape the hard carbon build up, & you should be good to go. I replaced my A4's EGR with a brand new Wahl part from Eurocarparts which came out at well under £100 including exchange of the old one.

 

[liam.wtf]

Temp will be in the engine module measuring blocks in VCDS. EGR is easy to remove, just 3 torx bolts, & unclip the pipes. Carb or brake cleaner a stiff toothbrush, an implement to scrape the hard carbon build up, & you should be good to go. I replaced my A4's EGR with a brand new Wahl part from Eurocarparts which came out at well under £100 including exchange of the old one.

Thanks! I’ll load up vcds and see if it shows anything odd. Too knackered now to give the EGR a clean especially as it’s dark outside and freezing cold! If I get time I’ll do that in the morning too, if not I’ll hope for the best that the fuel additive has worked! Will also give the engine a good run before the MOT as I’ve heard that can help

 

[Gazwould]

Remove fuse 31 and retest .

 

[liam.wtf]

Remove fuse 31 and retest .

What does that fuse do?

 

[Gazwould]

Cuts the fueling drastically .

 

[liam.wtf]

Cuts the fueling drastically .

Thanks! Will give it a go... sounds like a sneaky one hahah

 

[Gazwould]

Yep , new cheat device , lol .

Obviously resolve the issue , but this gives you time .

 

[liam.wtf]

Yep , new cheat device , lol .

Obviously resolve the issue , but this gives you time .

Wouldn’t be a VAG car without a cheat! Thank god MOT doesn’t require reverse lights on older cars!

Will get it resolved for sure (or more likely get a new car before then anyway!) could probably do with an EGR clean...

 

[Gazwould]

You can disable egr by pulling and plugging the egr vac line without eml if build sticker usually bottom right has OGE .

If it has OGZ then the egr has ecu monitoring and will throw eml .

 

[liam.wtf]

You can disable egr by pulling and plugging the egr vac line without eml if build sticker usually bottom right has OGE .

If it has OGZ then the egr has ecu monitoring and will throw eml .

Which one would be the vac line? And which sticker? Would it be on the EGR itself?

Also, passed the MOT!

 

[Stickystuff]

Sometimes just an oil and filter change can improve emissions. Old oil can gunk everything up and putting some fresh in with a new filter can make a massive difference especially if it’s not been serviced for a while


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[Gazwould]

For egr disable , is the top vac line not being touched .

OGE / OGZ found on build sticker inside service book or in boot .

A new thermostat will provide better results than a service and any gunk is going to be inevitable with a working egr as normal crankcase oil vapour combines with soot gunking up the egr and inlet manifold .

With egr disable there are several benefits including engine oil stays cleaner for longer and earlier turbo spool because all of the exhaust gasses are spinning the turbo !

 

[stevey83]

When did the car last have a good service?