R

rjohnstone

New Member
Can someone help pls.

I have a Classic Range Rover 4.2 LSE V8 (1993). On start up when cold the idle speed drops when in drive and on some occasions cuts out. Once warm runs very well.

To date I have done the following to try and rectify this:.
1. New Plugs
2. New HT leads (and in correct firing order)
3. New Distributor cap and rotary arm
4. New stepper motor

And I will fit a new coil today.

I think it may be something to do with the automatic choke. I would really appreciate if someone could help on this

 
rjohnstone said:
Can someone help pls.

I have a Classic Range Rover 4.2 LSE V8 (1993). On start up when cold the idle speed drops when in drive and on some occasions cuts out. Once warm runs very well.

To date I have done the following to try and rectify this:.
1. New Plugs
2. New HT leads (and in correct firing order)
3. New Distributor cap and rotary arm
4. New stepper motor

And I will fit a new coil today.

I think it may be something to do with the automatic choke. I would really appreciate if someone could help on this
Click to expand...

Looks like you have done most of the ignition side so could be fun and games on this one. There is no choke per se, the ecu looks at the afm and coolant sensor to determine how much enrichment is needed and adjusts the By-pass air valve (stepper motor) accordingly . There is also the neutral switch to detect load input from the gear box.

It may be worthwhile resetting your base idle speed, checking the ignition timing, check the output from the throttle potentiometer and also check the coil (and ballast resistor if fitted).

One other thought, check that the advance retard works properly. The acuum advance unit does pack up, disconnect the vacuum pipe from the plenum, remove the dizzy cap then suck on the pipe, you should see the base plate move. Then gently rotate the rotor arm back and fore, it should mmove a small amount and you will hear the advance mechanism moving. If it is solid, you will need to strip the dizzy.

Hope that helps.

PS forgot to suggest check the coolant temperature thermistor (sensor input).
 

Thanks for your reply.

I have tried all the above and the following, but still no luck – any more suggestions pls..

  • Cleaned out the idle control valve
  • Renew temp sender unit
  • Adjust base idle speed
 
Well, guess you got a real tricky little gremlin in there then.

Next step has to be find a 14CUX ECU (that is known to work) and substitute it for your own, also try substitution of AFM. If that doesn't solve it, it's time to start running flying leads from the sensors to make sure you haven't got a duff connection/broken wire.
 
BTW, have you checked you don't have a small vacuum leak somwhere. It could be something really obscure that has nothing to do with anything we have been on about so far. For example, is there any evidence of a split/leaking hose attached to the plenum (including the cruise control!!) are you sure the plenum housing is properly sealed.

Just a thought, but may be worth checking.
 

Hi there

Sorry what US A 14CUX ECU and AFM – I am new to this (not very mecahical minded)

Ps: I live in Braintree and trying to find a place where I can get a diagnostic test done as surely that would tell me – not having much luck at the mo.

Thanks for your help
 
The Lucas 14 CUX is your ECU - the black box that controls the fuel injection system. It is the brain for the engine. It is a closed loop injection system.

There is a thread on the forum that has some other details - I think somewhere in the Discovery section. However, plugging it in is not really the best way to go, it is an unnecessary expense, I know I went down that route.

Get hold of a working ECU, plug it in and see what happens.

The AFM is the air flow meter. On yours, I believe it will be a Lucas 3AM Hot Wire air flow meter, sometimes called the air mass meter.

You might have a 5AM Hot Wire AFM but the system is essentially the same, either way, try and get hold of a working AFM, plumb it in and see what happens.

Have you downloaded the workshop manual from Rave? (if not do a search for Rave on the forum).

If the engine is mechanically sound the answer is electrical, you just have to find it. This WILL test your patience, don't quit - it WILL be worth it.
 
classic kev said:
The Lucas 14 CUX is your ECU -

The AFM is the air flow meter. On yours, I believe it will be a Lucas 3AM Hot Wire air flow meter, sometimes called the air mass meter.

You might have a 5AM Hot Wire AFM but the system is essentially the same, either way, try and get hold of a working AFM, plumb it in and see what happens.

quote]

If you findout that you have problems with your Air Flow Mass meter these can be repaired! For a good adres see: ECU Repair Centre, Car Electronics Repair Service and Remanufactured units they also repair other Land Rover parts like, cruisecontrol, seat and mirror memories etc.
Click to expand...
 
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