Low Idle

[enak]

My engine has a low idle at times and can some times stall after starting when hot... The idle doesn't seem rough, just low.

I've cleaned the idle bypass valve and checked the operation.

I've replaced the MAF sensor.

Engine has done 142K now.

What else should I check/ replace?

[waveydavey]

It would help to know what the engine is

[enak]

:D 4.2l '93

[Range Rover Blues]

Just exactly how low?

It's possible the ECU is missing an input, you can do a basic system check using the Haynes manual and a multimeter.

Do the revs increase when you switch on the A/C, or the heated front screen? or stick it in D

[enak]

Low = below the 500rpm marker.  Sometimes it can struggle almost stalling.

The rev's do increase when you switch on the AC.  But not when put it in drive and my front screen doesn't have the heater elements.

What is the multimeter test?  I don't have the haynes manual... just the workshop manual.

Thank you

[Range Rover Blues]

There's almost a page of sensor checks that you can do yourself with just a multimeter, that way you can check the basic functionality of the EFi system without paying £30 and hour for diagnostics.  It could well be something simple.

BTW, as well as checking the idle bypass, have you checked the base idle speed? that's around 500 RPM IIRC, the idle bypass lifts the idle speed to 600 or so.