Emissions and uneven tick over.

[VINER]

Can anyone help. My 2001 elise failed MOT on emissions. At tick over its very uneven going from 1500 to 500 rpm constant with some slight black smoke and holding at 3000 rpm the engine is still very lumpy and very high emissions.Have replaced lamna sencores pre and post cat and new cat fitted.

[Justin S]

Do you have an IACV ( Idle Air Control Valve) on the inlet.This gives a variable airflow to the inlet to allow tickover.If you do have one, it may need cleaning out. Also check for airleaks. I found my variable tickover was caused by a breather coming off the rocker cover to the inlet manifold.

[NWTony]

Could be your inlet manifold gasket.

[VINER]

Have looked at valve and nothing much there to clean How would you clean it., But would this cause the high emissions problems.

Edited by VINER on Monday 2nd March 19:53

Edited by VINER on Monday 2nd March 19:54

[Justin S]

the valve is a steppermotor that fluctuates relative to engine speed.If it sticks it will cause massive air changes in the inlet and the car to never balance its idle.Remove the plug in connector and see if the car idles any better.You might get an engine management light up and it may take half a dozen engine starts to clear after being plugged back in.If it idles better thats the problem. You will need a torquedriver to remove the 4 bolts and clean out with carb cleaner or just get a new one for £30 ish.

[VINER]

Removed valve and cleaned, Valve is moving and does not change tickover when valve plug removed.
Have checked for any air leaks.Could be a visit to lotus to be pluged in and see if anything comes up.
Unless any other ideas.
Thanks for the advice so far.

Edited by VINER on Tuesday 3rd March 17:14

[Justin S]

I think that a visit to anyone with a plug in device to find out what is wrong is the next bet. Could be various things, such as faulty crankshaft sensor etc loosing signals. For the car to be running and occaisional sooting, could possibly the ecu trying to maintain an idle and when the revs drop is increasing fuel and air to keep it running.

[S Works]

Is it a Sport 160? If so, that'd be the Friday afternoon map

/sorry, couldn't resist. Best of luck in getting it sorted.

[VINER]

Thanks for the help....Visit to Lotus ,problem resolved within mins. Throttle Postion sensor at fault.

Edited by VINER on Thursday 12th March 03:18