Ax - MOT failure on emissions

[Jaf]

1994, 1.1 petrol, single point injection.

CO tickover 0.41 (last year 0.17)
CO acceleration 0.56 (last year 0.28)
Lambda 1.022 (last year 1.020)
Temperature 72

Engine was a bit cold. But engine does hunt slightly. The Lambda is about 4 years old. Have changed air filter and checked spark plugs, been for an "Italian tuneup" but engine still hunting. My CO tester is old and won't behave! I've popped some cleaner in the petrol tank. I would risk going back to the test station, with a properly hot engine, but its 40km away.

Any advice?

[wheeler]

Are you able to read live data of the oxygen sensor? Failing that if you dont have a 2 pin adaptor for diagnostics can you read the voltage of the signal wire on the oxygen sensor? with the engine warm & at idle it should fluctuate between 0.1v - 0.8v

[Stickyfinger]

On my single point AX (now Jim's) the hunting was only cured once the throttle body potentiometer was replaced. It ran VERY rich during this time.

It was causing the odd cut-out as well.

I will ask Jim the details later as he is visiting me this very moment.......in my garage helping a mate recommission a nice late Xantia 2.1 Exclusive Estate.....("Nice", other than some outer sill welding)

[Jaf]

Oh yeah good idea, thanks wheeler. I'd forgotten I can do that! Tomorrow I'll have a go.

I went to talk to the local mechanics, 2 different garages, neither has a CO meter. 1 suggested I go back after a nice drive. Came home, tried to book retest but couldn't, so I went anyway. Closed! Plonker.

The engine is smoother though, maybe 1 more tune up will do it.

Sticky, thanks. Did it ever "hiccup/ stutter" going round big corners. Mine has been doing that for years.

[xantia_v6]

Given that the MOT lambda reading has not changed significantly, I think that the issue was probably a cold catalytic converter.

[Stickyfinger]

Yep it did....or just died for a bit............however, |I would say a number of things "could" cause similar type symptoms.

[Stickyfinger]

Throttle body potentiometer was replaced on the AX (998cc) , throttle body potentiometer was cleaned on the Saxo (1.1cc) which started to show similar symptoms.

## O2 sensor went back to normal, normal operations returned.

[Jaf]

Whoop whoop! Passed retest.

Didn't get the lexia out as weather was horrible (laptop needs mains power), so can only be the fuel cleaner and 150km of driving like a boy racer.

Plus engine running much smoother, find out tomorrow what she's like on the corner she doesn't like.

Thanks again.

[Jaf]

Oh and there was an identical ax at the test place. Would have made a great photo!

[Stickyfinger]

Triffic.......