Idle from cold

chrisdenton · May 12, 2005

This is an old chestnut I know but I'm running out of ideas. My S2 won't tick over until warm.

Things we've done so far:-

1. checked vacuum lines ok
2. changed temp sensor, idle control valve and air flow meter.
3. checked throttle possition switch ok
4. checked cable back to ECU
5. checked fuel pressure
6. Swore a lot

My next move could be to change the ECU but this sounds expensive as we havn't got a spare.

Any body got any ideas

Fen · May 12, 2005

Flywheel sensors?
Check wiring so that ECU is actually getting the reading the new sensors you have fitted (especially temp) are sending?

chrisdenton · May 12, 2005

Thanks Fen

We've checked the sensors at the ecu end and alls ok. I'll check the fly wheel sensors out today. Excuse my ignorance but what do the sensors measure (probably flywheel speed) and why would this only cause problems from cold?

Fen · May 12, 2005

You're getting beyond my technical knowledge now but I believe they can lead to erratic running. It may not be possible for them to affect only cold idle but it's cheaper to check them than replace an ECU!

chrisdenton · May 13, 2005

I've checked the vacuum lines and they appear OK but I dont know if there routed correctly. Does any one have a diagram? Also when I removed the line from the black plastic cylinder at the rear off side of the engine bay(I think its the charcoal filter) I got a long hiss of air, either sucking or blowing I,m not sure. I suspect this is normal and does it prove my vacuum is OK?

eastendr · May 13, 2005

The black cannister is the vacuum resovoir for the heater controls

Guest · May 13, 2005

A broken or leaking vacuum line will give you issues when running, not just prevent easy idle at cold. I suspect it's the ISV. How did you check it to prove it was OK? I don't run with an ISV at all, and I do have idle isses exactly as you describe when cold.

I found this on rennlist which may help test the signal from the DME. If this doesn't work out, then you may have a DME problem rather than something easier/cheaper!:

"The ISV is a bi-directional motor that is controlled by the DME, and it should not have any power applied when the ignition is off.

I would start by removing the electrical connection and check the pins for voltage. The center pin is ground and the outside pins are +12 volts.

To control idle the DME switches +12 volts between the outside pins. 12 volts on one pin closes the valve, and +12 volts on the other pin opens the valve"

If that works out OK, you could try removing the ISV, bunging the ends of the pipes where it came from, and checking if it opens/closes correctly. Although I suspect the only way of really checking the ISV is to replace it with a known good one. I just sold one too, or you could have borrowed that. Sorry!

Mike

Fen · May 13, 2005

To be fair I took it at face value the ISV is good because it's been tested, but until I read that I had thought that would be the problem.

My S2 cab didn't idle from cold and it as a dirty ISV / idle control valve or whatever you want to call it.

Guest · May 13, 2005

Maybe I'm betting cynical, but I never take it that until it's A: been checked over by Bosch themselves, or B: replaced, then it's fully tested. Too many years of Lucas/Triumph electrics I guess!

Mike

chrisdenton · May 13, 2005

ORIGINAL: pikey7

Maybe I'm betting cynical, but I never take it that until it's A: been checked over by Bosch themselves, or B: replaced, then it's fully tested. Too many years of Lucas/Triumph electrics I guess!

Mike

Your right to be cynical Mike, I always am. The ICV is brand new so is the temp sensor and the afm is a reconditioned unit. Only thing left is the ECU.

Anybody got a spare I can try out on a sale or return basis?

Diver944 · May 13, 2005

Chris I sympathise with you, my own S2 has done this for the past seven years. No-one has been able to get to the bottom of it, though the ISV is most likely but requires the intake manifold to be removedso we've lived with it. After 30 secs of running it idles fine[8|]

I now think of it as a quirk of the car. It'll get fixed when the Ninemeister custom intake and supercharger get fitted (circa 2015)

Fen · May 13, 2005

I got mine off on the cab without removing the manifold. More importantly I got it back on too. I had to remove one rubber pipe, that was all.

Guest · May 14, 2005

Chris, Did you check that electrical connection at the ISV?

Mike

chrisdenton · May 14, 2005

ORIGINAL: pikey7

Chris, Did you check that electrical connection at the ISV?

Mike

Mike

I,ve just checked the connection. Mines only got two pins one is 0V the other is permanantly at +12V does this sound right?

Guest · May 14, 2005

Wow. Not sure Chris. Let me do some reading up on it. On first impression, the 0v would be a ground but permanently at 12V should mean something is open permanently or closed. If you have low idle, I would say closed.! Did you take the measurments once the engine had warmed up too?

I'll get back to you.

eastendr · May 14, 2005

Idle speed valve should have 3 conections. Earth centre and +12 applied to one end to open, other to close - supplied directly by the DME control module.

Guest · May 14, 2005

Rick, that's on our 8V cars. I'm not sure if the 16V had something different. Maybe a spring open solenoid or something? Hence I wanted a bit of time to check with the manuals & things.

Mikie_gb · May 16, 2005

Idle speed valve should have 3 conections

My 'S' had a 2 pin connector. They sent me the three pin connector unit which I returned and the correct two pin one was supplied. This was the first two pin one they had ever seen. The S2 may also have this unit. One to earth and one back to the DME control unit. On the three pin units two wires return to the DME 'control unit.

Information obtained from wiring diagrams.

Guest · May 16, 2005

Thanks Mikie. I've dropped the ball on my 16V wiring diagrams. Good to know it only has two connections.

Chris, unfortunately, I can't find a test for this one. Like I said though, In my (small) mind, the voltage output from the harness should change as the car warms up. That should then operate the solenoid in the ISV. If there is no change, then I would suggest either the temp sensor is faulty (though you say you've replaced it), the TS is connected wrong, there is a broken wire somewhere in the TS or ISV circuits, or the ECU is giving you trouble.

Mike

944Turbo · May 16, 2005

On the 8v cars there is a link in the plug under the flat round cover near the bulkhead that disables the ISV for when you are setting the tickover. Might be interesting to try a bypass and see if it makes any difference. IIRC the idle adjustment screw on the 8valves has an o-ring on it that can get damaged and cause a leak (or the screw fall out), if the mixture, idle speed etc. were set with it warm and leaking could you have issues when cold?
Tony