P38A Elastic Trickery problems.

Thank you for your input.

Petrol and LPG.

I can't get the battery checked for a couple of days, but will certainly do so soonest. The battery is not very old, but if it is below par, would it not give me a more predictable and/or continuous problem ? I am not very electrically-minded, which I suppose is yet another reason for not having a P38, (much less a P37½ )

Pression de Gonflage said:

Thank you for your input.

Petrol and LPG.

I can't get the battery checked for a couple of days, but will certainly do so soonest. The battery is not very old, but if it is below par, would it not give me a more predictable and/or continuous problem ? I am not very electrically-minded, which I suppose is yet another reason for not having a P38, (much less a P37½ )

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Low battery volts is a well documented cause of random faults on the P38's, invest in a cheap DVM.

+1 on cheap DVM. Usually about £10-£12 on Amazon. Probably similar in France ?

pwood999 said:

+1 on cheap DVM. Usually about £10-£12 on Amazon. Probably similar in France ?

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Even less on AliExpress

pwood999 said:

Probably best to sort the idle speed first. Could be a variety of things, but check the usual suspects like:

• IACV
• Clean Throttle Body
• Fix any air leaks (check inlet pipes, and LPG pipes between injectors & manifold.)

Might also be worth cleaning all the Engine ECU contacts, plus all the sensor & injector connectors.

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I didn't even know what an IACV was until I looked it up. I'm still not sure where to find it.

Likewise the throttle body. What is involved in cleaning that ? Remove it ? Wipe it with a rag ? Dismantle it ?

"...cleaning all the Engine ECU contacts, plus all the sensor & injector connectors...". I think that is going to be beyond my capabilities, so I may have to as Monsieur Renault in the village if he will have a look at all of these items. Are they common to "cooking" cars, so are they things he is likely to understand ? ( I will translate for him.).

Thanks again.

pwood999 said:

+1 on cheap DVM. Usually about £10-£12 on Amazon. Probably similar in France ?

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I have now acquired a DVM, or rather I have got what I think is a multimeter. So all I have to do now is work out how to read it and I can report back. What sort of numbers should I expect to find if the battery is good or bad ?

Not exactly a propos Range Rovers.but just a small aside.

I have said that I would probably visit our local village Renault garage. I had forgotten that this being France it is no longer that simpler.. The road to the village is cut into the side of a cliff alongside a little stream, which you may have heard of, called The Dordogne. One of the hazards has always been that with any rain, snow or ice, the cliff is inclined to shed chunks of itself onto unsuspecting tourists. It has been decided to stabilise the cliff,yet again, so the road has now been completely blocked for three months and we are offered a 15 kilometre detour. Nothing is ever simple when, with a little bureaucracy, it can so easily be made exceeding awkward.

Pression de Gonflage said:

I have now acquired a DVM, or rather I have got what I think is a multimeter. So all I have to do now is work out how to read it and I can report back. What sort of numbers should I expect to find if the battery is good or bad ?

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Battery voltage with engine running needs to be 14.7 volts or a bit more. After standing with engine off for an hour you should see 12.7 volts.

I think that's what I was wanting to know. Thank you.

Is there any deviation from those numbers which would be "near enough" or is any slight deviation bad news ?

Pression de Gonflage said:

I think that's what I was wanting to know. Thank you.

Is there any deviation from those numbers which would be "near enough" or is any slight deviation bad news ?

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13.8V is standard alternator output unless it has been upgraded. 14.3 V might just cut the mustard for a calcium battery but 14.5V or above better. That might cook a normal lead battery but I think most have a bit of calcium now. 12.6V standing is fine and the v8 can probably start as low as 12.3V.

The IACV can be cleaned by blasting some carb-cleaner or brake-cleaner through it.

Engine ECU would be last resort stuff.

Grrrrrr said:

13.8V is standard alternator output unless it has been upgraded. 14.3 V might just cut the mustard for a calcium battery but 14.5V or above better. That might cook a normal lead battery but I think most have a bit of calcium now. 12.6V standing is fine and the v8 can probably start as low as 12.3V.

The IACV can be cleaned by blasting some carb-cleaner or brake-cleaner through it.

Engine ECU would be last resort stuff.

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You would be hard pushed to find a car battery that is not lead/calcium these days. Any semi sealed battery that requires no topping up is lead/calcium.

Is the gearbox oil level correct ,fluctuating revs ,or random gear changes could even be a faulty xyz switch ,,does the dash show the correct gear,,,ie D for drive when it plays up , and said before low power can upset all ecu,s,,..

Datatek said:

Battery voltage with engine running needs to be 14.7 volts or a bit more. After standing with engine off for an hour you should see 12.7 volts.

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I have just been discovering my new multimeter, and it shows spot on 14.7 with the engine running and flickering between 12.7 and 12.8 after leaving it for an hour. So at least we seem to have ruled that out...err haven't we ?

Gear box oil level appears OK. I believe this should be checked when hot and engine running, so that is what I did.

I have now booked the car into Monsieur Renault's emporium for next week; He agrees that cleaning the throttle body is a good start, followed by cleaning or changing the plugs.( I wonder which he will choose to do !).

Pression de Gonflage said:

I have just been discovering my new multimeter, and it shows spot on 14.7 with the engine running and flickering between 12.7 and 12.8 after leaving it for an hour. So at least we seem to have ruled that out...err haven't we ?

Gear box oil level appears OK. I believe this should be checked when hot and engine running, so that is what I did.

I have now booked the car into Monsieur Renault's emporium for next week; He agrees that cleaning the throttle body is a good start, followed by cleaning or changing the plugs.( I wonder which he will choose to do !).

Click to expand...

Just because the voltage output is correct it doesn't represent the battery's capacity. Once a battery is fully charged you need to leave it to settle down and do a load test on it. This will tell you it's capacity (storage) and not it's voltage.

Pression de Gonflage said:

I have just been discovering my new multimeter, and it shows spot on 14.7 with the engine running and flickering between 12.7 and 12.8 after leaving it for an hour. So at least we seem to have ruled that out...err haven't we ?

Gear box oil level appears OK. I believe this should be checked when hot and engine running, so that is what I did.

I have now booked the car into Monsieur Renault's emporium for next week; He agrees that cleaning the throttle body is a good start, followed by cleaning or changing the plugs.( I wonder which he will choose to do !).

Click to expand...

Auto gearbox level is checked cold with engine idling after running through each gear and back to park. If checked hot your oil level will be seriously low.
As Mark say's the voltage does not show the actual battery capacity but what you have is a good indication that it's OK. As there is a constant drain on the P38 you can get an idea of the capacity by checking the voltage again after 24 hours standing and again after a longer period. The voltage will drop rapidly if the battery capacity is low.

Mark Piercy said:

N

Just the voltage output is correct it represent the battery's capacity. Once a battery is fully charged you need to leave it to settle down and do a load test on it. This will tell you it's capacity (storage) and not it's voltage.

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...err, "a load test" ? Please, Sir...

Pression de Gonflage said:

...err, "a load test" ? Please, Sir...

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A load test puts a defined load across the battery to see how many amps it can provide, lots of amps are required for starting for example thus the CCA rating on batteries, Cold Cranking Amps.

Datatek said:

Auto gearbox level is checked cold with engine idling after running through each gear and back to park. If checked hot your oil level will be seriously low.
As Mark say's the voltage does not show the actual battery capacity but what you have is a good indication that it's OK. As there is a constant drain on the P38 you can get an idea of the capacity by checking the voltage again after 24 hours standing and again after a longer period. The voltage will drop rapidly if the battery capacity is low.

Click to expand...

Seems that what I had read about gearbox level checking was incorrect. Prior to hearing that, I had always checked it when cold on the assumption that it would have drained as low as it could get in the box. I should have stuck to that assumption. Presumably, if hot, much of the oil would up and about amongst the cogs.

I shall check the level tomorrow as well as the voltages.

Pression de Gonflage said:

Seems that what I had read about gearbox level checking was incorrect. Prior to hearing that, I had always checked it when cold on the assumption that it would have drained as low as it could get in the box. I should have stuck to that assumption. Presumably, if hot, much of the oil would up and about amongst the cogs.

I shall check the level tomorrow as well as the voltages.

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The engine MUST be idling when the level is checked.

Datatek said:

The engine MUST be idling when the level is checked.

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This almost brings me full circle, as idling is frequently too fast to justify the word. I shall have to wait until it decides to settle back to a normal 750.