Poor fuel economy - Terrible CO emissions...

[Third Rail]

Hi all,

Just had the MOT on my MK3 2.0L Golf Cab, CO emissions came back at 10%!!!! (legal is 0.3%). The car just started to have poor fuel economy, getting about 280 miles from a full tank. I had a new lambda sensor last year, but what else should I be looking at?

Thanks for any help.

[Santiago]

Coolant temperature sensor possibly failed in such a way as to tell the ECU that the engine is always cold.

[itavaltalainen]

What engine is in there?

10% CO ? no way that's only temp sender (you can check this easily with a multimeter, I posted a how to here a few times, search will find it).

Something else must be seriously wrong....

Could be that lambda is faulty again or it's wiring but also other things.... could be leak on injection valve seal, faulty valve etc...

Can tell more with engine code.

[clancy]

I'd scan the car for any fault codes, sounds like something far more than just a sensor

I'd also run an engine flush

[Third Rail]

What engine is in there?

10% CO ? no way that's only temp sender (you can check this easily with a multimeter, I posted a how to here a few times, search will find it).

Something else must be seriously wrong....

Could be that lambda is faulty again or it's wiring but also other things.... could be leak on injection valve seal, faulty valve etc...

Can tell more with engine code.

It's a 1997 2.0L 8v cabriolet. I had the head gasket done last year and they fitted a new lambda when they did that as it struggled to get through the emissions then too. It's getting about 280 miles to a full tank of fuel too, not great all round.

[Bandit127]

I think it could be a temp (or MAF) sensor. Other people on here have had similar problems with a temp sensor.

Definitely scan it. You will probably have codes relating to either sensor if one of them has gone.

[Dalo Harkin]

for 10% id say your cat is fooked