Would Dipetane help in this case?

dooroy

A friend has a 2004 Passat 1.6 petrol with 150 K mls on the clock.
It failed its NCT last week due to high CO , see readings below :

Oil Temp : 85 degs

Low Idle (850rpm)
CO 0.30vol% PASS
HC 59ppm N/A

High Idle (2657rpm)
LAMBDA 0.99 PASS
CO 0.52 vol% FAIL/REFUSAL
HC 52ppm PASS

Car was serviced about 4K mls ago - plugs , air filter, oil and oil filter. Its running very well , not using oil and this is the first time emissions were a problem.
Would adding Dipetane or similar to the fuel be enough to improve the CO reading.
Any advice /suggestions appreciated.

Cerebrum

It might, it really depends on how it's usually driven.
Remember, if it's added to the fuel, run that tank of fuel through the system with some hard driving to burn off any excess carbon.
If he could leave the car running outside the test centre, it may help also. Ye'll need every little bit to squeeze those high idle CO figures below 0.3%, so get that cat a bit warmer

biko

I think high idle limit is 0.20%, either way the car is running rich.

Check air filter, is it dirty?
Does car sound like it has a leaky exhaust?

Probably best to change air filter anyway (and hoover out the filter box).
Also consider changing oil (and oil filter) and cleaning MAF.

rex-x

biko wrote: »

I think high idle limit is 0.20%, either way the car is running rich.

Check air filter, is it dirty?
Does car sound like it has a leaky exhaust?

Probably best to change air filter anyway (and hoover out the filter box).
Also consider changing oil (and oil filter) and cleaning MAF.

How do you figure its running rich? the lambda is .99 which is pretty much bang on. The car is running correctly looking at the readings but the cat has lost too much of its ability to remove co (which is its only job remember). An airfilter or oil change is not going to do anything here.

There is a chance that some diptane and a very spirited drive to the test center to get the cat as hot as possible will get it to scrape through but you may be looking at replacement unfortunately.

fancy pigeon

Try this along with an Italian tuneup

In Halfords, roughly €20 (click the pic)

The guy who sells this stuff tells me it can work well for NCT emissions fails
http://jmbreen.ie/product/jlm-petrol-catalytic-converter-cleaner-250ml/

Cerebrum

All of those cleaners will work much the same. They're just oxygenates to burn off the extra carbon (soot).