bit rough at low revs and emmissions all over the place

[ewan221]

Had car in at local garage getting the chassis scraped and waxoiled and asked him to clean the stepper while it was in as car runs a bit rough under 20 mph. The stepper was all fine but he described the emissions as being all over the place.

Any thoughts on where to start ? - the speedo does not work under 20 mph could this be related ?

[blitzracing]

There is an speed input on the ECU but it should not affect the emissions, just the idle if the signal is missing. Poor fuel control at low speed could be AFM, failed lambda, or even a misfire, but theres not enough info to go on really.

[ewan221]

Well was out playing in car all day and apart from it being a bit lumpy at lower speeds it seems to be running well but as I have nothing to compare it with I cant be sure. It idles at a steady 900 rpm doe not appear to be a misfire but if I get time tomorrow will pull a plug. My Dad (no expert but thinks he is ans he was a engineer in the mercahnt navy 40 years ago !!!) is adamant its running lean due to an air leak

Im thinking maybe will ask one of the local PHers if they could take it for a run and see what they think