Starts "rich" when warmed up

[Dave JRH]

Good afternoon,

My 400HC starts without any problem from cold, but when running at normal temp, it appears to start "on choke" with black smoke emanating from the rear, also i need to nurse the throttle for a few seconds until the richness has subsided otherwise it refuses to tick over.
I have cleaned the stepper motor valve and ensured the sensors on the exhaust are in position and connected and cleaned the air filter

Bit stuck now, any clues gratefully accepted

Thanks in anticipation

Dave

[blitzracing]

AFM on its way out.

[977]

Swap out the engine coolant temperature sensor for the ECU... Cheap, 2 minutes, often a cause of issues.

[977]

Also the bible has a table that allows you to check the resistance and see if it is reading correctly when dunked in hot water of various temperatures.

[Dave JRH]

Thanks for the reply, i have ordered a replacement temp sensor (Lucas part SNB802) Will report back once i have fitted it

Thanks

Dave

[brett84]

Do you mean when you restart once it's warm?
Mine does the same thing, copied this from an email Shaun (ms2 tuning) sent me, solves my problem
When you switch off the engine hot .. the water pump obviously stops and the engine heats up the water in the block (heat soak), but the stat is closed ... so the radiator cools. Then when you start it again a short time later .. the temp in the water around the sensor is cooled because the cold radiator water runs past it .. so the ecu over fuels the engine .. it chokes up and eventually stops. Usually you can solve this by 'blipping' the throttle a few times .. up to say 3000 rpm .. to flush the water around the system and clear the fuel in the cyilinders

[OleVix]

brett84 said:

Do you mean when you restart once it's warm?
Mine does the same thing, copied this from an email Shaun (ms2 tuning) sent me, solves my problem
When you switch off the engine hot .. the water pump obviously stops and the engine heats up the water in the block (heat soak), but the stat is closed ... so the radiator cools. Then when you start it again a short time later .. the temp in the water around the sensor is cooled because the cold radiator water runs past it .. so the ecu over fuels the engine .. it chokes up and eventually stops. Usually you can solve this by 'blipping' the throttle a few times .. up to say 3000 rpm .. to flush the water around the system and clear the fuel in the cyilinders

The temp sensor sits in the inlet manifold

[brett84]

yeah right next to the stat.
Mine was doing the same thing tonight. Won't idle if starting once the engine was warm, it starts then the revs drop and it stalls. But if I revved it a couple times it would tick over fine

[Dave JRH]

Yes Brett, the same as mine, but i am still going to change the sensor as the rear panel on my car is black from the black smoke, so something is not quite right

Dave