Mot fail due to emissions, possible causes?

[Antsa]

I took my car for MOT today and it failed the emissions test. I have oil leak to the turbo hot side. Is it possible that it causes emissions like this? What else could it be?

Left side shows idle and right side fast idle.

Emissions.jpg

[Antsa]

Here's a pic from underneath the car showing the oil leak between the center housing and exhaust housing. Not many months ago the turbo was rebuilt

20210304_150353.jpg

[CoupeWannabeS2]

I'm not sure that the oil leak would be an issue for the emssions.

My car failed MOT a couple of years ago on emissions, and it turned out the lamda sensor had failed.

Worth plugging you car into vagcom, as this could guide you straight to the problem.

[Antsa]

I will pull the codes first thing tomorrow and see if there is any. The lambda sensor has never been replaced while I have owned the car so it should be propably changed anyway.

[Antsa]

I pulled the codes before removing the turbo this morning. All I got besides the engine rmp and speed signals (engine was off) was the idle speed adaptation limit reached - intermittent. I think that does not give me any hints on the emission problem.

The turbo will be sent to the company who rebuilt it to find out the cause for my oil leak. I will also order a new lambda since I have no idea how old the current one is.

Hopefully I can put the turbo and new lambda back in next week and have another emissions test made and see if these had any effect.

[newsh]

I pulled the codes before removing the turbo this morning. All I got besides the engine rmp and speed signals (engine was off) was the idle speed adaptation limit reached - intermittent. I think that does not give me any hints on the emission problem.

The turbo will be sent to the company who rebuilt it to find out the cause for my oil leak. I will also order a new lambda since I have no idea how old the current one is.

Hopefully I can put the turbo and new lambda back in next week and have another emissions test made and see if these had any effect.

New lambda sorted my Avant last time it failed.
Ages ago the coupe was running rich due to a fault with the temp sensor on the back of the head, ECU thought the coolant was cold and made it run rich, can’t remember if there was a code.
Did you do a boost leak test?

[Lago Blue]

Antsa,

Could the 'idle speed adaptation limit reached - intermittent' be the ISV and/or ECM hinting at a possible vacuum leak, that results in too much fuel pressure at idle, which may be the engine speed that the emissions test was done at?

[Antsa]

New lambda sorted my Avant last time it failed.
Ages ago the coupe was running rich due to a fault with the temp sensor on the back of the head, ECU thought the coolant was cold and made it run rich, can’t remember if there was a code.
Did you do a boost leak test?

I did not do a boost leak test yet, I will do it once I get my turbo back and installed. I'm a little afraid of blowing up my oe turbo -> maf hose since it expands quite a lot when it sees pressure

[Antsa]

Antsa,

Could the 'idle speed adaptation limit reached - intermittent' be the ISV and/or ECM hinting at a possible vacuum leak, that results in too much fuel pressure at idle, which may be the engine speed that the emissions test was done at?

It might be so. Although if there was a leak would it be intermittent I will have to do some testing once I get my turbo back

[Lago Blue]

Just a guess as I'm not sure how that code is triggered, perhaps the ISV is bouncing off its' fully-closed end-stop as it cycles?

[johne]

I would go for a new lambda sensor first but make sure you get a genuine Bosch one in a box with a seal, even so still costs less than 50 Euros.

[Antsa]

I will get a bosch one, cheap brands only give you a headache

[Antsa]

I ordered a new Bosch lambda today. Also got the turbo back and they said there is nothing wrong with it and possible causes are clogged turbo oil drain or breather system. The oil drain seems to flow freely to me and the breather system valves are relatively new. Also the flame trap was cleaned well. So I really wonder what else could cause it

I did change the oil and air filter together with removing the turbo so everything should be good there once I put all back together.

I hope I can fit the turbo and lambda sensor tomorrow and have a new emissions test made next week.

[Antsa]

New lambda fitted and air filter changed and it made no difference. The figures are basically the same as last time, HC too high on idle and CO% too high on fast idle. Any suggestions what to do next?

[Jaswan]

Another train of thought...

Is the leak coming from the oil return?

Your turbo was recently rebuilt, possibly the return is blocked causing high pressure withing the CHRA and it's pushing past the seals?

Jase.