BXProject

[mat_the_cat]

OK then - this has me baffled. D6C engine, Motronic 4.1 with 2 row ECU, installed in a 205. The problem is cutting out when cold and idling (say the first 10 minutes of a journey), runs fine once warm. I've narrowed it down to the idle valve not operating, although 12V is present at one of the terminals, and there is continuity at the other back to pin 33 on the ECU. Bought a new idle valve, same problem. Next idea was coolant temperature sensor - perhaps the ECU is being told the engine is hot all the time therefore not raising the revs (I thought it unlikely as it seems rich enough to start easily even when very cold). Anyway, resistances checked out fine and a swap with a new one didn't improve things. I'd previously checked that the TPS operated exactly as the butterflies closed, and it did. Someone suggested an air leak from the breather system, which I have blanked off with no change.
I had a thought this weekend that the TPS wasn't operating electrically, and hence the ECU wasn't knowing when the throttle was closed. From looking at the wiring diagram it seems like the TPS is a simple changeover switch, not a potentiometer. Checking with a multimeter showed once set of contacts closed as the throttle was shut, but the other set of contacts didn't close when the throttle was opened. I can't see how this would affect the idling though, but it doesn't seem as it is working correctly? What I have done is disconnect the idle valve, and it still starts fine, needs a foot on the throttle for the first 30 seconds or so and the runs as normal, revs maybe a tad high at just under 1000rpm.
We've lived with the problem since I did the engine swap, it does very few miles anyway so didn't cause us issues but now we are trying to sell the 205, it seems to put people off. There's many many beers waiting for anyone who can help!

[Vanny]

water temp sensor makes between fork and naff all difference i reckon, but i guess you could try shorting the fecker out? I assume the fail state is 'cold engine' so if it fails then the revs should already be increased, consider it a reduction in revs when warm rather than the other way around. I'm basing this on Bosch theory rather than knowledge.

ICV, known problem causer, i've got two in stock as spare (one brand new!), the trick i've been told (and worked to recover the one on the car) is fill the fucker up with WD40, leave for a day or two and drain and refit.

I dont believe the TPS acts as a TPS on the valver. In my mind the logic works that the second the TPS comes off idle there is a click inside signifying to the ECU to move out of idle map and onto normal fuel map. The throttle opening sucks more air into the engine, moving the AFM, which feeds back to the engine to increase the fuel. I can't be arsed to get the blue book and check but thats how it works in my mind, and the reason a duff AFM can really screw with the engine. What happens when the TPS is moved to end of travel? I think the Motronic system has a max throttle position where it knocks off the AC, but i could be confusing with modern cars?

Air leaks into the manifold will always fuck with the system if its down stream of the throttle, but i suggest that this would still cock things up when hot. You'll start to get run away or near stall when hot.

I think Doc is really the man for this (or 205 gti drivers), he is afterall the doc!

PS have you checked the wiring continuity and Motronic connector?

[mat_the_cat]

Checked the continuity for the ICV, but nothing else. I should add that the replacement (pattern) temp sensor cause the fuel economy to drop to about 15mpg, so it was back on with the original. But that suggests that all the wiring to that is OK. Nothing happens wit heth TPS even on max throttle, no click, and nothing makes contact. But there is a click and the other contacts are broken the moment the throttle is opened.
Also been advised to look inside the AFM and make sure the wiper is making good contact with the tracks. Opened it up and all looked good, a gentle tweak to adjust the pressure again made no difference.

Cheers for the advice Vanny, I'm not too familiar with modern car electronics (grew up with points and carbs!) but am learning slowly! Will see what the Doc has to say...

[Vanny]

oh, i thought this was a thread about a 205? If its a modern car then you need a CAN bus analyser and the diagnostic port codes, then you'll be able to see exactly whats up.

[mat_the_cat]

Sorry, yes it is about a 205…to me modern car electrics means anything with electronic injection!

[docchevron132]

what Vanny said is all good.

The TPS is just a switch, and indeed it should also switch at full throttle to shop the AC, although it's a moot point since I gues the 205 doesn't have AC!

I'd be looking very carefully at the AFM here.
And the plug to it. Even a tiny bit of shit on the pins can fuck it right over like a $20 crack whore.
Cant rememebr the ohms range it works over off the top of my head, but worth checking that the resistance increase is linear whilst moving the flap.

Only other thing that comes to mind is a leak on the inlet manifold to head gaskets, had one on mine, caused much the same symptoms, shut up when it was hot since the expansion in the head sealed it..

[Bx Bandit]

Well I know far less than Vanny and Doc on such matters, only to say that my 16v used to cut out as well (when cold) and then be a bitch to start despite being an excellent starter when starting from cold if left over night! (I have Motronic 1.3).
It doesn't do it now and AFAIK I've done nothing to rectify the problem (despite trying and doing what you're doing) the possible 3 exceptions being:
1) Making ALL air inlet connections tight/sound and checking/fixing leaks/cracks
2) Cleaning all connections, giving them a little twist and greasing them lightly with copper grease
3) sounds odd but......it was stood for a year and at times with no battery connected. The ecu resets after 15 mins with no battery (or so I've read somewhere)

The ICV i think gets a pulse signal rather than a steady 12v (makes sense I guess) which you ideally need an oscilloscope to read (but fuck knows what you do after that!)

I still have a (warm) idle problem which isn't ICV related. Doc has said this before to me that valvers don't like standing and I'm convinced mine is better through daily use.

Anyway, it's a PUG 205 so who gives a shit!

Even a tiny bit of shit on the pins can fuck it right over like a $20 crack whore.

x alot!

Finally, Matt have you something called the CAPS demo? Sounds strange bit it's a Motronic 4.1 bit of software (quite neanderthal TBH) but may help.....

[Vanny]

15 minute reset? Bah humbug, this isnt a modern ecu, there is no limp home mode and thus nothing to reset. If the klight comes on then just power on through, the ECU wasn't programmed to care. My klight comes on a treat after you've hammered it for a bit, ease off and its straight off, just a contact some where getting hot and or loose. And unlike a modern car which has a BUS of CANs, and sub CANS and LINs and multiplex bollox, when you ask the motronic ecu it tells you whats wrong rather than having a stab in the dark.

[Philhod]

CANs, and sub CANS and LINs

Ah I'm understanding now. I remember LINCAN very well. You dont see them in the supermarket very much these days though

[mat_the_cat]

Cheers guys, it is appreciated.

I'm confident there are no air leaks in the rubber hoses, BUT Doc's theory about the inlet manifold gasket looks plausible. Which would be a bugger as someone has been there before me, and it looks like I'll need a special round kind of allen key to remove it. I wonder whether Halfrauds sell them... I wonder if whoever rounded them off was barking up the same tree?
Who gives a shit? Well I do as we need to sell the thing! Actually it's fucking good fun, but not a car I'd want long term. Just not 'me'.

Never heard of CAPS demo, in fact I wouldn't know where to plug it in. It's so long since I did the swap I can't remember whether there was a diagnostic socket (of sorts) on the original wiring loom. Ah well, I've got a few pointers to check at the weekend so fingers crossed and I'll let you know.

[docchevron132]

There will be a diag socket, 2 pin job, but it's fairly useless.
Being the 2 row ECU it wouldn't have a K light, and the diag socket wouldn't work anyway.

Rounded off hex bolts... back tot he oversize torx bit and a bloody big hammer!

Seriousley though, if I thought Kate could handle the power without killing herself I WOULD buy that and give it to her, but I know she would kill herself in it, and I really wouldn't want that...

What bandit says is right actually, to an extent, whilst the ECU isn't a clever thing, infact it's quite basic, but it will store fault codes, these can be wiped by pulling the battery off for 15 mins, or using a proper diag tool.
Again though, that assumes the diag socket works, and I've NEVER yet found a D6C equipped witha 2 row ECU that does.
Mine included...

The ICV is a PITA quite frankly, although whilst chasing a different but similar problem with mine, and suspecting the ICV, and getting arsy with the car quite alot I discovered the the ICV was fully closing up in an attempt to pull the idle down. The reason was the 2nd butterfly wasn't quite closing off everytime. When it did every so often it would catch the ICV out and stall the car.
So could be worth checking the butterfly is fully returning aswell...

[Way2go]

CANs, and sub CANS and LINs

Ah I'm understanding now. I remember LINCAN very well. You dont see them in the supermarket very much these days though

Thinking of the ones attached to the Park eh? Are they your taste in music?

[Philhod]

No wrong track (ged it)

I was refering to a range of tinned veg from a long time ago

[Way2go]

I see..................

[Bx Bandit]

That's the one Doc - clearing the fault codes. I did check and have a clean up around the butteryflies but it may be worth a revisit for a more thorough check - one blip on the throttle tends to re-set it.
Anyway, Matt I'm sure you know this but go steady removing the inlet mani studs - piss easy to shear off and a bugger get out!

[Vanny]

who cares if you clear the fault codes, i mean really, it makes no difference as it doesn't date stamp the faults. Motronic fault logging is pretty cocking pointless to be honest, what you really need is a Doc, job done.


I've never had a problem getting mani bolts out, i shall be taking more car in future though.

[docchevron132]

Erm, well yes and no really..
See, if you change some bits, and clear any stored faults, if they reappear, then you know they are back... kinda thing like... erm. yeah..

Inlet manifold bolts tend to ok as long as some ham fisted arsepiece cretin hasn't been there before with the crapulike socket set...t
It's a bit easy to over tighten them and rather fuck the threads up in the head aswell....

Go on then, I'll bite, what the fuck is a Doc?

[Way2go]

Go on then, I'll bite, what the fuck is a Doc?

When I read it I thought he meant you. So you think maybe not.....

[Vanny]

See, if you change some bits, and clear any stored faults, if they reappear, then you know they are back... kinda thing like... erm. yeah..

Just because it reports a fault in system 'X' doesn't mean the fault was actually in system 'X', more likely it was i system 'Y' and had a knock on effect, hence your better off using a wealth of knowledge than trusting the diagnostics of a pre 95 car, you could go chasing ghosts ofr weeks at huge expence otherwise.

[docchevron132]

Go on then, I'll bite, what the fuck is a Doc?

When I read it I thought he meant you. So you think maybe not.....

I'm thinking it must be some "in the know" diag machine or some shit?

Just because it reports a fault in system 'X' doesn't mean the fault was actually in system 'X', more likely it was i system 'Y' and had a knock on effect, hence your better off using a wealth of knowledge than trusting the diagnostics of a pre 95 car, you could go chasing ghosts ofr weeks at huge expence otherwise.

Well, yeah, but it does give you an idea of where to start.
Equally, the whole system is pretty fucking simple, so all you really need is an oscilloscope and a half decent digital test meter to check the lot.

It's all fucking witchcraft anyway!