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[warp]

Hi all, having a little prob with my XJ 4.0l, with the recent cold mornings it seems to struggle due to lack of fuel when you accelerate, but seems to be ok after 1/2hr when things have warmed up. The engine starts up fine and will running ok on tick over. Thought it could be either the lambda sensor, mass air flow or something else.

Any ideas?

[Tank]

If the lambda sensor goes it will be stuck in its last setting so when cold could be running too lean,like when you forget to use the choke,or maybe its the cold start,if there is one on a jeep.Had a similar problem on an XR3i years ago,cold start went and it was a bitch inn the mornings in winter,not so bad in the summer though.Dont know about the air flow but im guessing there must be a way of testing it,and the lambda maybe,although Dr Mike will be the one to give a definative answer i am sure

[isle of man]

The Lambda does not effect anything till the engine/catalytic converter gets to normal operating temperature.

[Mike Pavelin]

The Lambda does not effect anything till the engine/catalytic converter gets to normal operating temperature.

..........and it doesn't have a mass air flow meter.

[isle of man]

I'm thinking distributor cap and rotor.

[warp]

thanks for that will try a new rotor arm and cap

[Mike Pavelin]

 If it's taking 1/2 hour to warm up, I'd change the thermostat.

[Jonny Jeep]

The O2 sensors are heated and the computer starts using them as soon as they are hot enough (around 350°C) as determined by a timer within the computer. This takes little more than twenty seconds as can be seen from my scangauge showing the switch to closed loop mode. Engine and cat don't need to be anywhere near full operating temp.

[JamesH]

I'd go for new rotor arma dn dist' cap, new leads, then lambda sensor if I was changing parts. If you are on LPG it will definitely be ignition parts.

[warp]

Yeah it's got LPG with the LPG though it's slightly different when you slow down the rev's drop then pick up, when using petrol it struggles to accelerate sometimes misfires.

Think your right though with the arm and dissy cap they ain't much so i'll change em