D502 Idling Regulation(?) Problems

Hi folks, looking for a bit of engine expertise guidance if I may. Had my LM for over 18 months now, and I'm struggling to resolve a stalling problem (intermittent). It starts and runs perfectly well, but on quick decelleration when declutching/changing gear particularly (i.e. no throttle) the revs can die away with the engine effectively stalling - of course it refires once a gear is engaged at speed but it can die when coming to a halt. I tend to pre-empt that by just tickling the throttle as I pull up, but that's a pain!

This only happens when the engine has warmed up, and then it's unpredictable. It starts again instantly and always idles immediately afterwards. I took Lee's (Clee) advice last year and removed and cleaned the idling regulator but the problem persists. I'm open to ideas now - could the regulator signal be erratic/faulty? Didn't buy a new one 'cos I think they're around £130!

As far as I'm aware the car has always been serviced regularly (I put new bosch dist cap/rotor on last year so that should be fine). I don't use it enough, so that won't help, but there has to be a reason for the revs drop off. Oh, I've tried to replicate the stall by reving to around 2K then taking my foot off the throttle pedal (car static), but it seems to settle back to an normal idle each time!

Please help if you have any ideas - many thanks.

Paul T

Idle motors are cheaper if bought from Volvo.

Check the throttle microswitch is working every time (LeMans still have micros and not a pot?)

Try cracking the throttle stop screw open a tadge. Do this with engine hot and minimum load. You shouldn't be able to increase the idle (until you go too far) because the idle system will fight you. This will give the idle system a little more headroom. It's exactly the same as opening the brass screws slightly on the DeLorean. (except the GTA ECU cuts injection because of the idle switch, so it shouldn't make for a backfiring exhaust on overrun).

Idle motors are cheaper if bought from Volvo.

Check the throttle microswitch is working every time (LeMans still have micros and not a pot?)

Try cracking the throttle stop screw open a tadge. Do this with engine hot and minimum load. You shouldn't be able to increase the idle (until you go too far) because the idle system will fight you. This will give the idle system a little more headroom. It's exactly the same as opening the brass screws slightly on the DeLorean. (except the GTA ECU cuts injection because of the idle switch, so it shouldn't make for a backfiring exhaust on overrun).

Thanks Martin, could do with a pointer to the location of both as the manuals (I say manuals because the Le Mans set up seems closer to the 610 in some respects and the GTA manual really doesn't help much) do not clearly identify the throttle microswitch or the throttle stop screw (well they might but they probably use different terminology!) and as I have limited knowledge of the workings of the PRV, I don't want to tamper with the wrong bit! And whilst I apologise for what may be a 'numpty' question to you, how do I actually check or consistency in the working of the throttle microswitch?

I searched the forum last night and found that Chas had exactly the same symptoms with his Le Mans in 2008 but the thread never concluded so I don't know if he resolved the issue. I've PMd him but no response yet. What he described precisely matches my problem so if he did find an answer, it's probably what I'm looking for too.

Thanks for your help. Paul

Paul,
on a GTA turbo, the throttle switch is the black box on the side of the throttle body, passenger side.
It is held on with 2 screws and there is 3 wires coming from it.
Basically it has 2 switches in it.
1 to detech that the throttle has no foot on the peddle, and a 2nd to provide full fuelling when at about 70%.

Just undo the 2 screws, with engine off and while you are in a quiet garage, and rotate the switch untell you just hear the microswitch inside it click.

ok?

Paul,
on a GTA turbo, the throttle switch is the black box on the side of the throttle body, passenger side.
It is held on with 2 screws and there is 3 wires coming from it.
Basically it has 2 switches in it.
1 to detech that the throttle has no foot on the peddle, and a 2nd to provide full fuelling when at about 70%.

Just undo the 2 screws, with engine off and while you are in a quiet garage, and rotate the switch untell you just hear the microswitch inside it click.

ok?

Thanks for the advice, will do that. Paul T

I wrote this a few years ago on another forum and it may help you?

Stalling whilst hot especially when slowing down at junctions or slip roads can be caused by more than just the idle control valve.

After the idle valve has been cleaned the next area to look at would be condition of the throttle body/butterfly. This can get gummed up due to oil contamination which also can block the small air by pass bleed hole which allows air bleed during over run & very small throttle openings.
To clean use proper “carb cleaner” and it is best to remove the throttle body even though it can be done in place, if cleaned without removal , the engine will splutter and misfire for few seconds after the first start up. Whilst cleaning it is also good practice to disconnect the battery to allow the internal capacitors to discharge and so reset any running parameters.
To reset idle control after cleaning start the engine and allow to settle for a few seconds, then turn headlights, heater fan & hazards on for 15-20 minutes & allow to idle. Then switch these consumers off and let the engine idle gain for another 10-15 minutes.
If cleaning the throttle body & idle valve does not resolve the problem, I would not recommend adjusting the throttle stop to overcome any stalling unless they have been already moved and if so they will require resetting as per manual along with the position sensor.
Another cause of stalling is road speed information that the ECU receives. Even though the main speedo is working, it has been know that if this information is not been received or is sporadic it can cause stalling when slowing down, the problem here is that you need the equipment to see what the ECU is getting & interpretating.
There are more possible causes but again you will need the equipment to see what is happening to them before any replacement.

I wrote this a few years ago on another forum and it may help you?

Stalling whilst hot especially when slowing down at junctions or slip roads can be caused by more than just the idle control valve.

After the idle valve has been cleaned the next area to look at would be condition of the throttle body/butterfly. This can get gummed up due to oil contamination which also can block the small air by pass bleed hole which allows air bleed during over run & very small throttle openings.
To clean use proper “carb cleaner” and it is best to remove the throttle body even though it can be done in place, if cleaned without removal , the engine will splutter and misfire for few seconds after the first start up. Whilst cleaning it is also good practice to disconnect the battery to allow the internal capacitors to discharge and so reset any running parameters.
To reset idle control after cleaning start the engine and allow to settle for a few seconds, then turn headlights, heater fan & hazards on for 15-20 minutes & allow to idle. Then switch these consumers off and let the engine idle gain for another 10-15 minutes.
If cleaning the throttle body & idle valve does not resolve the problem, I would not recommend adjusting the throttle stop to overcome any stalling unless they have been already moved and if so they will require resetting as per manual along with the position sensor.
Another cause of stalling is road speed information that the ECU receives. Even though the main speedo is working, it has been know that if this information is not been received or is sporadic it can cause stalling when slowing down, the problem here is that you need the equipment to see what the ECU is getting & interpretating.
There are more possible causes but again you will need the equipment to see what is happening to them before any replacement.

Very useful and interesting thanks. When you say that you need 'the equipment' to pinpoint any other causes do you mean an XR25 diagnostic kit? Paul T.

Very useful and interesting thanks. When you say that you need 'the equipment' to pinpoint any other causes do you mean an XR25 diagnostic kit? Paul T.

That would be correct if you know someone with one and they know how to use it correctly other wise it's a Renault dealer who still has one or if not they will have to use the current diag equipment (CLiP) which should show most of the data required.
Some of the new generation Snap-on diag kits which some garages have, can show a limited range of data if the operator has the correct key, then it's down to how well they interpret the information displayed.

I've tried to read this thread three times, but keep getting distracted by Simon's avaitor!

...and yes, I'm easily distracted...

I've tried to read this thread three times, but keep getting distracted by Simon's avaitor!

...and yes, I'm easily distracted...

I just cover up the left eye

Concentrate guys..., it will soon come to you !

Paul, what's the pickup / throttle response like from idle i.e. just off idle as you start adding throttle? Is there any hesitation in the engine response? What about stamping her down on hard accel?

I'll have a check of the INJ R manual as I can't remember the LM set up. Can you give me the part number of the ecu, the S number?

How long has it done this, and had you made any changes (any degree odd) before this started happening?

Sounds like the idle valve is working correctly, does it appropriately compensate as you add load - lights and fans, and then come back down as you switch off the load? If it's playing up it'll usually not function at all, or stick up and the revs stay high.

As already mentioned the fuelling is cut on over run, and these points are preset on rpm. The reason it's more an issue after the engine temp has warmed up is that the water temp enrichment isn't cut until the engine is above 80 degC in the standard map. So at lower temps you will have increased fuelling, so anything in the fuel circuit causing restriction will net you a slightly lower delivery and hence increased sensitivity to this issue i.e fuel reg, vacuum connections, fuel filter etc..

May also have a poor map signal if the ecu connections and interconnects have corroded, don't forget this is the primary fuel reference signal utilised in the delivery calculation.

ps... I have the Fenix / Renix viewer kit, and will be some where close weekend after next... fancy checking out a daily drive car I'm considering buying 'tis on Ebay in Notts not easy for me to see (I'm down near Heathrow)?

Paul, what's the pickup / throttle response like from idle i.e. just off idle as you start adding throttle? Is there any hesitation in the engine response? What about stamping her down on hard accel?

I'll have a check of the INJ R manual as I can't remember the LM set up. Can you give me the part number of the ecu, the S number?

How long has it done this, and had you made any changes (any degree odd) before this started happening?

Sounds like the idle valve is working correctly, does it appropriately compensate as you add load - lights and fans, and then come back down as you switch off the load? If it's playing up it'll usually not function at all, or stick up and the revs stay high.

As already mentioned the fuelling is cut on over run, and these points are preset on rpm. The reason it's more an issue after the engine temp has warmed up is that the water temp enrichment isn't cut until the engine is above 80 degC in the standard map. So at lower temps you will have increased fuelling, so anything in the fuel circuit causing restriction will net you a slightly lower delivery and hence increased sensitivity to this issue i.e fuel reg, vacuum connections, fuel filter etc..

May also have a poor map signal if the ecu connections and interconnects have corroded, don't forget this is the primary fuel reference signal utilised in the delivery calculation.

Thanks for your interest, I'll PM you shortly but just to answer a few of your questions, I haven't noticed any hesitation in throttle response, not that I tend to push the car hard! The car has done this since I bought it. We drove it up here from Southend on a hot day nearly a couple of years ago and it stalled as I pulled up at a junction near Newark, then once again in the town. I have taken it out for a blast a couple of times without issue, but after cleaning the idle regulator the stalling seems to have worsened! Nothing else has been touched (just new cap/rotor) and I haven't checked ECU connections (not sure how anyway). I am no engine expert, so hesitate to mess about until I am sure what I am doing.

You make a good point about checking for idling compensation, and I will do that. I haven't noticed the idling speed shift before, but then I probably haven't been looking for that!

Will check the ECU number tomorrow.

PT

I've tried to read this thread three times, but keep getting distracted by Simon's avaitor!

...and yes, I'm easily distracted...

I just cover up the left eye

I prefer just covering up the right eye and not getting too distracted by the post my car idles fine

si21