Cutting out after 25 minutes

Hello

Difficult one to track down at the moment. My "93 RRC LSE 4.2 auto" drives very smoothly except on the odd occasion when the engine 'cuts out' momentarily and then restarts.

Over the last week or so it has become a regular occurrence. The pattern seems to be that after about 20 minutes driving, the engine cuts out 3 or 4 times in quick succession
· If we are moving then it picks up again and we carry on until the end of the journey.
· If I'm at lights or a junction, the engine stops. I select neutral and restart and off we go.
There are no faults on the ECU.

Does anyone have any ideas?

Thanks
Neil

check battery connections and earth connections, sounds like power loss cutting the engine. had it on my p38 where the earth lead popped off, i got a couple of beeps from computer beforehand but didnt link the two till after the event!!!

Battery conections are all good.

I've got a little more from the weekend as it happened again while I was gently reversing into a parking space. Cough, splutter and then stall. Started it back up and engine was the usual smooth V8. The next day I read the ECU and found the error "(48) IDLE SPEED CONTROL STEPPER MOTOR PROBLEM. ", which wasn't there the weekend before.

Some months ago I was getting "(17) THROTTLE POTENTIOMETER GIVING INVALID READINGS" errors with no real problems showing themselves. I cleaned all the wiring I could and this problem went away. I'm now wondering if the wiring is getting old and tired generally or if the stepper motor needs replacing - or perhaps something else?

cheers
Neil

I would check rotor arm, dizzy cap and ignition amplifier before getting stuck into tthe EFI. It might also be worth making sure you don't have any vacuum leaks on the plenum.

classic kev said:

I would check rotor arm, dizzy cap and ignition amplifier before getting stuck into tthe EFI. It might also be worth making sure you don't have any vacuum leaks on the plenum.

Click to expand...

Anyone? Expert feedback appreciated!

Do you think this will help identify the faulty component(s)?

Engine stutters/stops then starts and runs on for long or short periods before repeating same.


Rig up two 4/5 watt 12 volt bulbs (or 2V, 15mA LED's + 680 ohm resistors) on test leads into the cabin and connect one between coil +ve and earth and the other to coil -ve and earth. Mark the bulbs POS and NEG. Beware cables dont foul hot/moving parts (edited to add LED info, 20/10)

Start the engine and observe:

POS sensing the ignition input voltage is permanantly on,


AND

NEG sensing the pulsed voltage across the Ignition Amplifier flickers or is dimly lit.


Drive and have a helper note what happens when engine stalls.

If POS and NEG go out together there is an open circuit interruption of the 12 v feed such as a faulty wire/ignition switch,

OR

A short on the same circuit due to burned insulation.

If NEG comes full on the Ignition Amplifier (due to excess internal heat) or its associated wiring/earth has failed in open circuit mode,

OR


The pulsed input (ie Hall Effect) to the amplifier from the dizzy has failed or the associated wiring is faulty/shorting to earth,

OR


The Coil has failed in a short circuit mode (unlikely cos it would surely kill the amplifier methinks?)

If NEG goes out the Ignition Amplifier has temporarily failed in short circuit mode due to excess internal heat,

OR


the local wiring is shorting to earth,

OR


The coil has failed in open circuit mode due to insulation breakdown or internal heat.

Supplimentary:

Early Ign Amps have a finite life of approx 60-80000 miles and must always be refitted with thermo conductive paste.

Condensation inside dizzy plays havoc with electrics, Spray with WD40 and wipe dry, Likewise all external ignition components.

Ramon
Vintage Model Airplane and Rover SD1 3500cc Twin Plenum Vitesse

Had the same kinda trouble when i first got my RRC 92 3.9. I changed the CTS (coolant temp sensor £7) After doing the leads, plugs, dizzy cap (all genuine) it still never ran totally great. I then replaced the rotor arm with a genuine lucas one and it ran as sweet as anything, dont wanna tempt fate but it's still running ace.

Also done my airflow meter, potentiometer, and the stepper motor but found that the rotor arm made the difference.

Good luck

Hello Neil, You asked about: --------

NKG said:

Cough, splutter and then stall. Started it back up and engine was the usual smooth V8. The next day I read the ECU and found the error "(48) IDLE SPEED CONTROL STEPPER MOTOR PROBLEM.

Click to expand...

Apart from dealing with the idle speed control device, the inside of a plenum will get mucked up with crud-laden breather fumes, so galleries and throttle plate are vulnerable to blockage. When that happens, be aware that the amount of air being consumed at idle WILL be affected by this unwelcome goo, more so if the throttle plate is supposed to be set with a small gap between it and the tunnel.

After air leaks and electrical connection problems, the next most common cause of Efi issues is a dirty plenum and all the bits therein, so a thorough clean-up thereabouts will make a big difference to idle speed control.

http://www.vintagemodelairplane.com/pag ... num01.html

Some months ago I was getting "(17) THROTTLE POTENTIOMETER GIVING INVALID READINGS" errors with no real problems showing themselves.

Click to expand...

If you read about throttle pots on my pages you will see that when they go wrong they will cause significant fuelling problems and the nature of the fault is RANDOM.

http://www.vintagemodelairplane.com/pag ... Pot01.html

Both "dirty plenum" and "faulty throttle pot" are very unforgiving situations and the symptoms can only get worse over time, until dealt with, so if your events were simply one ignore them - for now!

or perhaps something else?

Click to expand...

Well, one of the current plagues in the Rover SD1 World is "Crud in the Fuel" and its getting more and more common.

It's as if the vendors are putting additives in the fuel to keep the engine clean that have the side-effect of also cleaning then inside of petrol tanks with the inevitable clogged filters and blocked fuel lines.

So, check your fuel supply is clean and filters in good nick.

Ramon
Vintage Model Airplane and Rover SD1 3500cc Twin Plenum Vitesse