Need some help with two error codes

[Van Black]

Hi guys,

I've been struggling with two error codes on my 07 A4 2.0TFSI:
P2187 lean AFR at idle
P0420 cat system bank 1, insufficient effect

I changed the DV on the turbo when I first got the car and did a timing belt change.
I changed the upstream O2 sensor and the codes still active.

Interesting thing is that I erased the codes and drove the car; codes came back on
after I hit a bump in the road. Maybe an electrical issue somewhere?

Another very odd thing is that the compression on all 4 cylinders is 9.5 bar (137 psi),
the car has supposedly 300 000 km, 190 000km on the dash.

Whenever the codes come on the fuel consumption goes up 10-15%, I get 9.2 l/100km (24mpg) outside of town.
In the city I do around 16 l/100 km.

I found some pointers on the forums but none that had both codes active, just singles.
It would point out to a bad cat and a PCV valve, or seals of the crank shaft.

Anyone else can give any advice on what to check?

[Okedokey]

Sounds like something that is reading air to fuel mixture - MAF? If the cat is blocked that may happen I guess, but someone else may chime in and correct that idea.

[Van Black]

Don't know what to say about the MAF, I've read on other threads that the PCV valve can lead to P2187. Thing is that the exhaust gasses smell a lot like unburnt gas so I'm thinking the actual
AFR might be too high, as for the high fuel consumption which might lead to a insufficient cat performance code

[Okedokey]

Sorry I cannot be more helpful bro.

[Van Black]

No worries Okedokey

[BenMTL]

Is this the 2.0 FSI engine?

Isn't under 140 PSI low? Should be 160+ psi I thought...

Definitely could be CAT, PCV, or MAF related....

[Van Black]

Is this the 2.0 FSI engine?

Isn't under 140 PSI low? Should be 160+ psi I thought...

Definitely could be CAT, PCV, or MAF related....

Yeah, 2.0, all 4 cylinders @140PSI-ish.
Could the piston rings be worn, I've never seen an engine wear equally on all 4s.
I'm gonna get a 3rd scan of the car and hopefully can rule out the MAF and rear
O2 sensor.
BTW audi says that factory compression should be between 160 and 200PSI, so you
basically can get an engine with 160 brand new, so in those conditions 140 after
200k km wouldn't be that bad :)

[Van Black]

Anybody else have any other hits?

[mfdk]

P0420 cat system bank 1 - is 99% related to the cat, i had the same code and although the cat will pass all the test when using vagcom its still not performing as it should hence the word "inefficient", of course for me buying another Cat was too much money as they go around 1k for new one, i ended up buying 034 HFC and never had the code come up anymore. Also buying a used oem Cat your risking of running into the same issue, i used the o2 spacer and passed emission without any issues.

Edit: i see you're from Europe, I'm not really sure what your options are as far as replacing your Cat.

[Van Black]

Thanks for the hindsight

As far as I know europarts sell the 034 HFC and spacer, it's on my to do list along with exhaust and intake.
I was thinking the cat code might be related to the AFR code: MAF reads too much air in the intake, ECU
gives it extra gas and then the CAT inefficiency error comes, there is a rather strong smell of gasoline behind
me some times

just a thought

[Van Black]

Just realized that when I did the timing on the engine I noticed a small fissure in the drivers side SMIC.
It's not very large, about 1/3" long and about a nail thickness in width (8x1 mm).

Could this be the culprit for my lean AFR code?

[Van Black]

Small update: Checked the PCV and the hoses. Everything checks out, except for an absurd amount of CB on the membrane and inside the valve.
I'll see if the IC cracked again next week. Also planing on doing a leakdown test next saturday

[Van Black]

Okay, took of the front bumper today, repatched the SMIC and hopefully AFR will go to normal.
What I've also found, to my great surprise, the hose that goes from the DV to the intake of the
turbo was loose. The banjo bolt that held it in place fell off at some point. Still getting CEL but hopefully
that's just the CAT.