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Discussion Starter · #1 ·
RR and engine have done 140k miles.

I’ve had an idle and stalling problem for some time now, but apart from that, the car works fine and the engine is very smooth.

When I start the car from cold I need to keep pressing the accelerator to stop the engine from stalling. After about 3 minutes the car will idle on its own. If I drive the car during this period, the engine will hesitate under acceleration, after this it accelerates ok.

When I drive the car (after the 3 minute period) and then come to a stop, the engine will stall. This happens during the first 10 to 15 minutes of a journey. After this time, the engine idles correctly when the car comes to a stop. During the 10 to 15 minutes I ‘left foot’ brake so I can press the accelerator with the other one. Every now and again, the engine will stall when the car comes to a stop after any duration of journey.

Sometimes, when idling normally, there is low howling noise from somewhere around the plenum chamber, but the engine idles ok.

When idleing from cold I've watched the ECU with a BlackBox Faultmate. Things seems to be working normally and I can see the stepper motor, potentiometer, O2 sensors, air flow and temperatures working normally.

I have replaced the following:
• Stepper motor and stepper chamber gasket.
• Accelerator Potentiometer.
• All the air pipes coming into the plenum chamber.
• Removed the plenum chamber and cleaned it out.
• Replaced both O2 sensors.
• New injector O rings, but same injectors.
• Fuel pressure regulator.
• Filter and flame trap that sit on the rocker covers.
• Coil.
• Distributor cap and rotor.
• Spark plugs and cables.
• Mass Airflow Meter.
• Alternator.
• Fuel filter.
• Checked base idle. The engine idles horribly here, with an RPM range between 360 – 650.
• ECU fuel and temperature sensors.
• Rocker cover gaskets.
• No consistent faults on the ECU.
• Timing is 8 btdc.

I would be interested in any ideas on how to find the fault or faults. I was wondering if the injectors need replacing, quite a large cost for all of them. Does anyone know how to check if an injector is good or not?

Many Thanks
NKG
 

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Replacing fuel injectors makes a "huge" difference. I replaced mine with Ford Mustang 5.0L 19lb injectors.

Do a search on Ebay for "Fuel Injectors 19lb 19# lb Ford Mustang TPI 5.0L 4.6L". I think there like $129 for all.
 

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you dont say if it has had a cam? as a worn cam sticking follower can effect it
i would reset the base idle first and retest 520 rpm +/- 20 rpm
are you using genuine cap leads and rotor arm
is the air gap on the dissy correct
 

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Discussion Starter · #4 ·
Hello

Thanks for the replies.

olmectec: The web site looks good. Out of interest, why did you get the Mustage ones and not the RR ones on the same site (ebay number 280457270563)?

stuart460: The cap and rotor are genuine, the leads are not; all put on last year. I've assumed the air gap was good as the car starts first time everytime, but you are right, I need to check that. The cam has never been touched. Any ideas on how to check the cam and followers?

The base idle is an issue. It will not settle down, 520 rpm +/- 60.

Thanks
nkg
 

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Ebay item number "280457270563" are for 3.9L V8. Since you have the 4.2L the 5.0L Mustang ones are for you.
 

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Discussion Starter · #6 ·
Hello

Having a look around the dizzy I see there is small black box attached to the side. Looking through the manual it would seem to be an "IGNITION MODULE/AMPLIFIER". Does anyone have any experience of these when they start to ware out?

Thanks
Neil
 

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NKG said:
Hello

Having a look around the dizzy I see there is small black box attached to the side. Looking through the manual it would seem to be an "IGNITION MODULE/AMPLIFIER". Does anyone have any experience of these when they start to ware out?

Thanks
Neil

Yes. On later cars (including your's I think) the amplifier was moved to the wing to avoid heat problems. If you look at the wire that comes out of that black box, you'll probably see that it plugs into an identical looking box on the inner wing. The box on the side of the dizzy is a dummy and is just for the 'remote' wiring to attach to.

My experience is that they are reasonably susceptible to bad earth problems. The amplifier sits on an aluminium bracket on the inner wing, through which it earths. You end up with bimetallic corrosion where the aluminium meets it's steel mounting bolt. I tend to take the whole thing apart avery now and again and clean up all contact points with emery paper. You can unbolt the amplifier from the bracket, but bear in mind that there is a heatsink grease compound between the two so be careful not to wipe it off.
 

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Discussion Starter · #8 ·
A bit of an update. Checked the timing and dissy air gap. All looked good.

I also checked the amplifier on the side of the dissy. On mine the amp is on the side of the dissy, there is no other module. There is one single wire running to the body as a ground, then there is a socket with two wires running up to the coil.

The next port of call are the injectors.

nkg
 

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Discussion Starter · #9 ·
Put on the new injectors, but that made no difference to the idle. The engine does feel a little more responsive on the motorways though.

Then put on a new distributor amplifier module. Had to take the dizzy off for this, which made it a very easy. I also reset the gap in the dizzy as this was on the small side of the gap stated in the manual.

After the dizzy was back on there was a real difference. Still doesn't idle perfectly when cold, but much better. I was also able to set the base idle with the engine remaining much more stable than before.

nkg
 

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I would still be inclined to look at replacing the cam and followers. How many miles have you done with the car? After 100k it is pretty much essential to change the cam, some of them have been knackered at 80k! If you are unsure or have no evidence of it being replaced, it's worth doing. My 3.5 revved and ran so much more willingly and smoothly when I

Not too expensive to buy the parts, and not too difficult to do the job either.

Have fun!
 
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