Cold mornings - hesitant start...

[rusgb]

Hi guys, I'm looking for some help. When the car (4.0, 1999) is cold, I think below about 5 degrees it makes a right arse of starting. Sounds rough and if you dab the throttle it almost stalls. Then you get to a junction and the revs go up to around 1,600 for about 5 seconds then it settles back to about 1,000 and will be fine for the rest of the journey. If I leave her for about 30-40 seconds after starting (i.e. warms up) she is then fine also. When the sun is out like today she is perfect... what's that all about then? Has anyone the same problem or any answers?
Rus

[ybt1982]

Mine does similar, apart from the 1600rpm thing. Someone told me it was the good 'ol Lucas 14CUX over fuelling when cold.

I have been known to be wrong before though so may be best to wait for someone who knows

[TV8]

Assumimg you ave no fault codes and generally everything is set-up properly, is the air flow meter an original or copy part?

I had cold start problèms for a while but a s/h Lucas AFM sorted it.

[gary58]

try cleaning the stepper motor

[JFReturns]

A case of TADTS...

But clean your stepper motor, butterfly valve in plenum, check sparks, shrouds, leads, vacuum advance pipes, dizzy cap just in case...

[blitzracing]

That 30-40 second bit on startup is the critical bit, it gives the ECU enough time to correct the mixture when the lambda probes heat up and give a reading, so the engine does not overfuel from that point. If you drive off straight away they tend to run a bit rich anyway (Range Rover mapping is not ideal at this point) and the ECU cant correct until the probes get hot. As also mentioned it could well be a sensor input is wrong in the first place (AFM or Temp), if its overfueling worse than normal.

[rusgb]

As always guys this is great feedback. I already feel reassured by the fact that I am not the only one. I will make the checks suggested!

[EGB]

Does happen sometimes on cold mornings. When starting avoid touching the throttle for 3 seconds after it fires. It usually settles down to tick over 900rpm. If it's a little rough (choke everfuelling as blitz says) give it a rev to 1500. Mine then settles ok. I think it's initial lazyness between ECU and cold sensors. Also give stepper a clean. Similar symptoms to my 40 year old Suffolk Colt lawnmower.

Edited by EGB on Thursday 2nd May 16:01