Random engine cut-outs

[fancsali]

Just bought a Roadster, and I love it. It's huge fun to drive, it looks awesome, but...

When driving around, sometimes the engine just stops without any warning sings. The dashboard clicks, and is lit up like a christmas tree; as if I just switched on the igntion. I can switch to neutral, and start it again right away. No need to wait. (I might have switched off the ignition and back again on some occasions, I am not sure anymore.)

Tried to get some error codes with a bluetooth OBD reader, but no luck. Clean as fresh snow.

I've done some research (partly in this very forum), and I was inclined to believe that it must be the crank sensor. But it doesn't seem to be connected to the engine being warm. Yesterday it did it just after leaving the driveway, it just stopped on the first corner. Then arriving back home after like 30 minutes of driving without any issues around town, pulling up to the gates, and it stopped again. A few days back it just cut out on the top of the Hammersmith flyover, when slowing down, and letting the automatic shift back. If anything, it's only happening at low RPMs. (I am not sure about this, but I might have had a little "pause" on the motorway the other day. Just the dash clicking, but the engine seemed to continue running. It might have push started itself.)

Also the earth cable could be a culprit, I've heard. The one in the engine bay is rather corroded, but I am a bit sceptical about this. It's hard to believe that a cable an inch in diameter could just stop conducting because of some rust.

Just to be on the safe side, I checked the key yesterday, but I can jerk it around as much as I like, the engine is completely fine, so it must be something else.

The only thing remaining is the SAM unit, I am gonna squeeze my head under the dash, and have a look. But then again, it seemed fine when I bought her. Also a blown fuse wouldn't act up like this, it'd completely switch off some parts of the electrics/electronics.

So, anyone any similar experience, tips, insights? Could it be the CPS, despite the thermal invariability? Or should I start with the earth leads? Or is it something completely different?

Thanks in advance.

[bob-in-dav]

Ok - first response - this may sound silly but a couple of owners have had a similar problem with a large bunch of keys hanging on the car key which has had sufficient weight to pull the ignition switch into a position where it would cut out.

[fancsali]

Well, I had been sitting in the parking lot yesterday for a while, pulling, pushing, and shaking the key vigorously. I must have looked rather odd. But the engine was completely fine.

[Thrumbleux]

Also the earth cable could be a culprit, I've heard. The one in the engine bay is rather corroded, but I am a bit sceptical about this. It's hard to believe that a cable an inch in diameter could just stop conducting because of some rust.

.

Start with the earths - they weren't that good to start with. You can just add an additional one in parallel. If you do that and mount it on the cylinder head, there will be a direct earth for the ignition coils. Check the battery one also.

[10:45PM]

Earth braid degradation can make a huge difference.. If it looks corroded, it's cumulative effect on volt drop across it when it matters can be crucial.
If you're a cheapskate try a jump lead across it to eliminate it after a test drive.

But I'd also check the obvious, battery terminals +&-, it's not unheard for them to never be tightened up.
Also alternator and starter connections just to close every link.
It could definitely be the CPS, remove it and check condition which might give you a clue , or just change it to eliminate it.

[Mr T]

When the crank position sensor failed on my wifes car, the engine would cut out slowing for junctions or just sitting idling. But it wouldn't restart for 5-10 mins, until it cooled a bit & only did it on really hot days.

I also had a fault code show up, using a cheap reader. At first I couldn't find a fault code but for some reason the reader I was using had 2 menu options for fault codes, it showed in one but not the other???

I think when the engine revs are up a bit, a missing pulse or two isn't so critical for the engine to run. When it drops to idle is when it matters.

Replacing the sensor isn't too difficult, you just have to be a bit patient & be a gynecologist...lol.

There is a guide here...http://www.evilution.co.uk/index.php...engine&mod=888

[fancsali]

Thanks for all the tips. It seems, despite everything, the earth leads and the CPS are my best shots.

I've ordered both, so I have to sit tight for a few days now. We'll see. Fingers crossed.

[EmilysDad]

Well, I had been sitting in the parking lot yesterday for a while, .....

Is that a bit like a car park .......

[137699]

From what you describe it sounds like a power supply issue - so earth leads are the first starting point.
This forum isn't blessed with many Roadster owners - you might want to register & bookmark this site for future reference: www.theroadster.net

[fancsali]

Well...

Almost, but no cigar. Or should I say, "figure this"?

Replaced the earth strap, and the sensor. First trip was wonderful. Smooth engine sound, smooth shifting, smooth drive. Drove for an hour without any issues, whatsoever.

Parked the car in front of the house, and wanted to move it in a few hours, and bam: Forgot to shift to reverse, revved it a bit in neutral, as soon as I realised (1500ish RPM), removed my foot from the accelerator, and the engine went. (Although I'd say this time it seemed to try to stay alive, seemed to come back for another stroke, before stopping.)

Restarted beatifully again, without any issue. But it seemed to have some other quirk this time: I think, despite being in A, the shifter was rather reluctant to switch gears. It usually lets me rev the engine, if I push it hard, but this time I could slowly accelerate for quite long time, and it seemed to keep the gears low. (Can't tell if it was 1 or 2, but it seemed to me it thinks I am trying to accelarate hard) Switched to manual, and back to auto, and everything went back to normal.

So, I'd be keen to hear any ideas you guys might have.

I am inclined to think it might be some short circuit. I've heard somewhere near the fuel pump there's a hotspot for the wire harness to rub against the tridion. Does anybody have any experience with this?

Also heard rumours about some voltage sensing wire at the battery, which loves to come loose, but I couldn't find anything about that despite trying to look in other languages too.

The only thing I did to the car between the two trips is removing the carpets? Did I ruin the SAM? Or the relay next to the key? Just by the looks they're OK. Also tried to reproduce the problem by touching them, but I can poke around both of them with my huge clumsy hands as much as I wish, it won't kill the engine.

I am completely puzzled, so any help is appreciated.

Many thanks,
Dan

P.S.: Indeed, the car is in the car park.

[fancsali]

Just noticed another, possibly crucial thing: while idling stationary, whenever I push the button to close the already closed window, it won't even move or make a sound, obviously, but the engine RPM goes down noticeably. As soon as Iet go, it returns to normal idling.

[tolsen]

That is normal. Window is hard up against the stops and window hoist motor draws amps causing load on engine.

[davros7760]

This issue has been cropping up regularly on The Roadster.net and I have suffered badly from this until my talented friend finally
tracked down the culprit on my roadster.

Check for copper oxidization on the pins to the ECU - a fine needle file and electrical contact cleaner should help (NOT WD40!)

As time passed the cutting out became more frequent and the time lag before I could restart got progressively longer - which is
consistent with increased oxidation build-up over time

[fancsali]

This issue has been cropping up regularly on The Roadster.net and I have suffered badly from this until my talented friend finally
tracked down the culprit on my roadster.

Check for copper oxidization on the pins to the ECU - a fine needle file and electrical contact cleaner should help (NOT WD40!)

As time passed the cutting out became more frequent and the time lag before I could restart got progressively longer - which is
consistent with increased oxidation build-up over time

Well, out of pure desperation I ripped apart the SAM unit, and found some rather curious corrosion around N11-8 pins 39 and 40. Guess what? That's CAN+ and CAN- going towards the ECU. So just as you say.

Cleaned everything around that are with proper electrical contact and PCB cleaner, and reinstalled the unit. Seems fine so far. (Although you have to make sure everything is properly plugged in, otherwise you'll have some very stressful time, believing you completely ruined your car. )

Fingers crossed, that this was the last thing.

P.S.: Will keep the thread updates, even if this was the solution. So others can learn from my adventure...

[fancsali]

First of all, thanks for the lots of tips, I think I've narrowed down the problem to a few things. Which on the other hand means, still haven't managed to get rid of it.

So, drove the car for a longer time, to see, what's up with the issue, and I found something really curious:

After driving for hours without problems, sometimes the ESP light just flashes briefly, and usually shortly after both the ESP and the ABS lights light up. (But the latter is not always the case) This seems to be a warning sign, that in 30-90 minutes there'll be issues. And usually there is. Sometimes it's just a few relay-clicks form the SAM, and the car restarts using it's own momentum

Other times though, the thing remains "off": One bar on the speedo, and still in gear. I feel physical pain stopping her like that on the kerb, and giving a proper jerk to the transmission.

But here comes the magic: If I let the SAM unit down, randomly poke around the cables, and push it back to it's original position again, usually the system comes back alive, which is usually indicated by a clicking noise from the SAM, and the 'one-bar' disappearing from the speedo. (Sometimes I need to repeat the above process a few times, or give the SAM a nudge.) This clearly suggests some connection issue around the SAM unit and/or the cable harness.

But there's the confusing side as well: I couldn't reproduce the error itself, by poking around there: So no matter how hard I "agitate" the SAM, and the cables, I cannot make it fail. So that'd indicate, it's not a connection issue, rather something else. Maybe I am just hoping, it's my actions that are fixing it, it's simply a matter of sitting still for a minute or two?

However, when it finally comes back, the ESP and ABS lights are almost always lit, and I need to remove the key, and completely restart the car, to make them disappear. (But then it's okay again, even for days, and hundreds of miles.)

So I am rather inclined to say it's some issue with the ABS/ESP unit (units?), or something between it/them and the SAM. But I am equally puzzled. Anyone had any similar issues? Where do I find the ESP unit? What to check on it? It seems to be something that's not really well documented on the internet.

Also I checked the reluctor rings, based on the little I could see while the car being parked on the street, I'd say they've seen better times. Does anyone had experience with that? Do you think that could cause something similar?

I do understand this seems to be a rather long thread, but if anyone has the mental capacity, to add something to it, I'd be really thankful.

Cheers in advance...