Emissions problem (U.K)

[marcjagman]

Okay, here we go. Took the old bus in for it's MOT this morning and it failed on emissions. Fast idle was fine but tickover was a bit depressing, runs on LPG. HC pass but still high at 529ppm but the CO was 5.47% and max allowed is 3.5%. So, what do you think? throttle body maybe? Has been on diagnostics and nothing coming up, no codes, nothing at all. Has been serviced too, 1999/2000 model, 4.0 V6.

 

[marcjagman]

Okay, here we go. Took the old bus in for it's MOT this morning and it failed on emissions. Fast idle was fine but tickover was a bit depressing, runs on LPG. HC pass but still high at 529ppm but the CO was 5.47% and max allowed is 3.5%. So, what do you think? throttle body maybe? Has been on diagnostics and nothing coming up, no codes, nothing at all. Has been serviced too, 1999/2000 model, 4.0 V6.

The O2 levels are correct and lambda's come up as working. Thinking of basics I can't think of anything other than air flow meter and throttle body, anyone else got any udeas?