Technical Running rich

[Jonna83]

rite this ain't my car with the prob its my m8's. Basically its running rich u can see black smoke coming out the Zorst when statrted and when cold it idles at around 500 rpm which we all kno is wrong . we r serving it later on 2day sparks,air/oil filter, oil etc. Anyideas y its running rich other than a service needed? its same age as mine 95 M with 9000 miles less. It does guzzle the petrol tho we both coverd almost the same distance 2 sounthend on saturday (i dun an extra 10 miles) and i'd used half a tank and he used 3 1/4's.

FIAT CinqueCento = Recycled Ferrari

 

[John H]

Assuming it's still the same when you change the air filter it's most likely the Lambda sensor.

If the sensor stops generating its (small) voltages the system thinks you're running lean ( low=lean ) and gives you a catalyser destroying rich mixture

 

[Jonna83]

hmm ahhwell we will find out in a couple of hours

FIAT CinqueCento = Recycled Ferrari

 

[Jonna83]

Added some nitrox Hotshot 2 it so there is a mixture of black and white smoke while servicing we uncoverd alot of 'Bodge jobs' it looks like its been neglected quite a few metal filing's in the old oil. But its now ticking over alot better still ain't cured the over richness tho any ideas?

FIAT CinqueCento = Recycled Ferrari

 

[Jonna83]

Im gonna take a guess that nobody kno's the answer then so ill share when i find out in the mean time ill post 2 my own topic alot

FIAT CinqueCento = Recycled Ferrari

 

[blitzen]

Hi m8,

John gave you a guess (mine would be the same, as I had happened to me): the lambda sensor might be defect

Cheers,
Marc

 

[Jonna83]

yeah i was thinking of suggesting that next 2 me m8

FIAT CinqueCento = Recycled Ferrari

 

[John H]

I don't know what else to suggest -
(AFAIK)
during warm up the mixture is determined primarily by ATS and CTS using a look-up table in the ECU. Not forgetting rate of change of TPS, or course..

When warmed up then sensors still give the first shot at mixture, but it's adjusted according to Lambda sensor voltages to feed the CAT. with a correct stoichiometric mixture of about 14.66 to 1 (air to fuel, by weight).

If your lambda sensor is shorted out the ECU thinks the mixture is lean and cranks up the fuel - giving poor consumption, and a cooked catalyser.

Any other opinions??