Engine Running To Rich

[SINGH182]

when starting my car cold or after a few hours, once its started the engine runs as if there is too much petrol going into the engine.

If i start the car and stand next to it i can smell excessive petrol fumes coming out off the exhaust when engine is cold, and sometimes warm. Ive had the car for almost a year now and only started noticing to problem within the last few weeks,

Is there anything that i could do myself to sort out the problem or does it need to be pluged into a diagnosis system?

many thanks

[dave1]

Pop into Lexus Coventry and see Craig on service desk. I have no doubt that he will be able to tell what the problem is. They are very helpful.

[Skotte]

I have the same problem on mine but I don't know if it is normal when the auto choke is on. Can't remember if it was like that to begin with.

Would like to know if you/they find a problem with the car.

[durg]

Is your engine check light on?

[adrian71]

if engine management light on could be an ignition coil thats gone down

[SINGH182]

hi,

no warning lights on, but have noticed a slight higer usage off petrol when driving aaround town though.

[KevLex]

I too would be interested in the outcome of this one. Mine smells very 'rich' on a cold start and I too suffer very poor economy around town.

I thought that the engine warning light would only come on if there was an 'emissions' related problem, which this sounds like.

The mixture will be enriched during the warm-up phase by injecting additional quantities of fuel. This will be controlled by the coolant temperature sensor. After the warm-up phase I imagine that it switches to closed loop control using the lambda sensor to maintain a stoichiometric ratio.

On an older car it would have been possible to just measure the CO content at the exhaust. This is not possible with a catalyst. Some cars have a sample point up-stream of the cat to allow CO measurements to be made. I'm not sure whether the IS200 has one.

Let us know what you find out.

[durg]

One other question - have you stood or walked round the back of the car and has a sniff when it has warmed up but the engine is not running? It could be a fuel breather leak somewhere.

It’s not unusual to smell a rich mixture when the car is starting up. It takes about 40-60 seconds for the catalyst system to warm up – the IS300 has a lot of catalyst volume, with two manifold catalysts plus an extra one. Once it has warmed up properly you should not be able to smell any fuel. The engine can produce quite a rich mixture and the catalyst can still cope with it. If it is running too rich (the point at which you can smell petrol at the tailpipe!) you can damage the catalyst system. Under these conditions the engine check light will come on to warn you. This is why I asked. It has been cold lately so the engine will be running quite rich at start-up. Do you do a lot of short journeys normally? If this is the case (and maybe have a go anyway) then take the car for a really good blast. It’s not an old wives tale that the MOT man tells you! If you get a catalyst exposed to slightly rich and hot conditions (you do this by driving the car hard and fast – don’t get flashed though!) then it has the effect of regenerating the catalyst and can improve its performance.

Generally it could just be down to the cold weather that has increased fuel consumption. It has been a lot colder recently! Hope this helps. Dave

[durg]

The mixture will be enriched during the warm-up phase by injecting additional quantities of fuel. This will be controlled by the coolant temperature sensor. After the warm-up phase I imagine that it switches to closed loop control using the lambda sensor to maintain a stoichiometric ratio.

On an older car it would have been possible to just measure the CO content at the exhaust. This is not possible with a catalyst. Some cars have a sample point up-stream of the cat to allow CO measurements to be made. I'm not sure whether the IS200 has one.

Yup - Once the catalyst has warmed up and is active then the closed loop running mode controls the emissions to lambda 1 (stiochiometric) using the engine-out sensor, with a perturbation of about 2% rich/lean to keep the catalyst active. If the car was running rich to the point you can smell petrol then you would also have CO at the tailpipe and should be able to measure it. But this would suggest the catalyst was &^%$£" and your engine check light should come on.