I've kept the S/S off on my Twinair to reduce engine wear during the first 2K miles, but have now put it back on. And there seems to be a problem:

S/S shuts the engine down properly most times, but then the engine starts back up almost immediately.

Any ideas what could be causing this?

Many thanks in advance!

Cold weather. It's normal, btw.

:yeahthat: and why did you think using it would cause extra wear in the first 2k miles

Most Easterly Pandas said:

why did you think using it would cause extra wear in the first 2k miles

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Because of all the stopping and starting on a "tight" new engine, of course Yes, yes, I know, "beefed up" starter and battery, but unless engines have become magically friction-free, I'm not buying the whole "it makes no difference" line from the manufacturers.

So you all reckon it's the cold weather then? Shouldn't the S/S system know that it's cold and not activate? Seems daft to have it flicker on and off at every stop when it knows what the outside temp is

Mine does the same thing and yes it's a complete pain in the arse. I've been waiting for some warm weather to check whether it works properly then or there's a problem in which case I'll take it in for investigation. When the engine is warmed up it stops for longer, but usually it's a max of 10-15 seconds. As I got it in september I've not had much warm weather to test it in really

nemchenk said:

Because of all the stopping and starting on a "tight" new engine, of course Yes, yes, I know, "beefed up" starter and battery, but unless engines have become magically friction-free, I'm not buying the whole "it makes no difference" line from the manufacturers.

So you all reckon it's the cold weather then? Shouldn't the S/S system know that it's cold and not activate? Seems daft to have it flicker on and off at every stop when it knows what the outside temp is

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But once an engine has warmed up the wear caused by SS is almost zero as its not going to be off long enough for the oil all to drain back to the sump

Why should SS not work below a certain temp, the whole point is to save fuel, which it is doing even if off for only small periods of time.

Most Easterly Pandas said:

But once an engine has warmed up the wear caused by SS is almost zero as its not going to be off long enough for the oil all to drain back to the sump

Why should SS not work below a certain temp, the whole point is to save fuel, which it is doing even if off for only small periods of time.

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S/S is disabled by design until the engine has warmed up. My S/S will kick in once the temperature has risen above 1/4 on the gauge. Once the engine has warmed up, there's no intrinsic reason I'm aware of why it shouldn't work normally, whatever the outside temperature.

However, it's also designed to restart the engine (or even not operate at all) when certain parameters are met. I'm thinking that those parameters are more likely to be met on cold days, when folks are using the lights, HRW, & heater - increasing the battery drain current beyond a certain limit will automatically restart the car.

One thought from my recent winter grille blanking experiments - if the heater is running with the engine off, the water in the heater matrix will cool down (quite quickly on very cold days), and as the heater circuit isn't controlled by the thermostat, the cold water in the matrix could shock cool the engine when it restarts.

I too thought it could be the other bits I have running because of the cold weather -- for example I've noticed that if you have the rear window demister on, S/S will not shut down the engine.

So I've tried some informal experiments to see if S/S will work as I expect (i.e. shut down the engine until I put the clutch down) and it has not.

I'll do some more formal experiments today -- no heater, no demister, no radio. Only headlights and running lights. That should work, right?

PS. I have ESP fitted -- could that be kicking the engine on in some way?

I think there is some guidance in the manual on when it will shut down.

nemchenk said:

PS. I have ESP fitted -- could that be kicking the engine on in some way?

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ESP has no bearing on S/S.

If any form of heating is on even on slow speed the matrix temp will drop to cold within a min or 2 at the most, so I suspect if any heating is on this will have a major contributing factor on the SS systems operation.

I too have the same experience with S/S.
It consistently stops, but restarts after around 9-10 seconds. I've tried turning all sorts of things on and off, but it makes little difference. It also seems to make no difference how long you've been driving the car for either. Therefore, a 45min drive will activate the S/S when you come to a stop, but it still restarts again after 9-10 seconds. Of course, if you're waiting for it, it'll wait around 20 seconds before restarting!

Mine was working perfectly normally when the weather was warm, i.e. stopping the engine and leaving it stopped for up to 3 mins. As soon as the weather got cold, it either doesn't stop at all, or stops and then restarts relatively quickly after stopping. I consider it normal, and will be quite sure it will start behaving 'normally' as soon as the ambient temp increases again.

Most Easterly Pandas said:

If any form of heating is on even on slow speed the matrix temp will drop to cold within a min or 2 at the most...

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Absolutely spot-on correct. However,

Most Easterly Pandas said:

...so I suspect if any heating is on this will have a major contributing factor on the SS systems operation.

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How can the car know? The coolant temperature sensor won't see the change until after the engine restarts & the water starts circulating again.

jrkitching said:

How can the car know? The coolant temperature sensor won't see the change until after the engine restarts & the water starts circulating again.

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if its got climate it'll have an internal cabin sensor, and don't hold me to it but upon removing the manual AC unit from a mk3 Panda in sure I was some sort of temp sensor sitting just in front of the matrix. So only time there might not be a sensor is on models without any sort of AC, and then it might just be a logic gate system installed to work out if interior fan is on and temp outside is below X then the engine needs to restart after Y amount of time?

You would have thought if it restarts the engine after only 9 or 10 seconds that the system would be intelligent enough to know it shouldent have switched off in the first place?

Mercky said:

You would have thought if it restarts the engine after only 9 or 10 seconds that the system would be intelligent enough to know it shouldent have switched off in the first place?

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You wouldn't be saving any fuel then would you, which is the whole point of SS.

So how much fuel is actually saved by switching on and off the engine for 10 seconds? I'd say switching off and back on for that short a duration probably uses more fuel if anything! I would imagine there is a minimum duration under which has a nil or negative impact on fuel saving and I'd reckon that duration would be more then 9 or 10 seconds. If the software is deliberately programmed to do so well one can only presume the designers got it right and it does save fuel but I find it hard to believe.

My grandfather was a Major in the Royal Army Service Corps and an engineer and he used to say the same thing - turning your engine off and on uses more fuel than you save, for short periods.

This is probably less so with modern ECU controlled fuel injection systems where there is less of a spike in fuel usage as the engine starts, but there must come a point when it is not worth turning off.

Most Easterly Pandas said:

But once an engine has warmed up the wear caused by SS is almost zero as its not going to be off long enough for the oil all to drain back to the sump

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Sure, but we still have the variance in fuel injection to start the engine, and the fact that we are spinning up rotating masses from standstill, which can't be good for the bearings.

loveshandbags said:

ESP has no bearing on S/S.

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I'm thinking hill-start or something... :idea:

Mercky said:

You would have thought if it restarts the engine after only 9 or 10 seconds that the system would be intelligent enough to know it shouldent have switched off in the first place?

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Exactly. And the car knows the outside temp, so if it is that it should really know not to engage S/S at all.