S2 takes a while to start, sometimes starts then dies

[nick9one1]

I've go a few issues that I think may all be related....

My S2 takes a while to start, it turns over fairly well but takes a while to fire up. This seems to be on both cold and hot starts.
Sometimes (not very often) when hot starting it sounds like it has caught, then splutters and dies.. it might do this twice before it fires up properly.
Idle is a bit high and slightly rough, wandering about 100rpm.
Once its running its fine (never stalls).
[blockquote]I've tried a few things already..
Re-tracked the AFM
Cleaned the ICV
Replaced Spark Plugs
[/blockquote]I noticed today that the high idle is probably a sticky throttle cable. When you pull the accelerator back with your foot it dops to 950 rpm (although still lumpy). So can probably cross that one off.
[blockquote]After some research I think it could be any of the following..
DME Relay
Distributor cap
HT Leads
Low fuel pressure (does anyone know the thread for the fuel rail end cap?)
Leak down test (probably not this but would be good to remove the possibility)

[/blockquote]Any other suggestions would be appreciated!

 

[GlennS]

Check the speed / reference sensor. A symptom would be no "bounce" from the rev counter when cranking.

 

[Jonny944CS]

... and the wiring loom to said sensors - these can cause frustratingly intermittent issues, particularly when cranking.

The fuel rail thread is M12x1.5 I think.

 

[nick9one1]

Thanks, I'll check both of those.

High idle was the throttle cable being too tight. I suspect a previous owner tightened it as they didnt know how to adjust the ICV.

 

[Eric_Oz_S2]

Could be the O2 sensor as well. Unplug it and test the O2 output with a volt meter.

 

[nick9one1]

ORIGINAL: GlennS

Check the speed / reference sensor. A symptom would be no "bounce" from the rev counter when cranking.

Thanks - but the rev counter does bounce when I crank. Is that conclusive?

Could be the O2 sensor as well. Unplug it and test the O2 output with a volt meter.

ORIGINAL: Eric_Oz_S2

Could be the O2 sensor as well. Unplug it and test the O2 output with a volt meter.

Thanks - Didnt think about this one. As O2's only last about 60k I've ordered a new one anyway. Should arrive today/tomorrow.

 

[GlennS]

ORIGINAL: nick9one1

ORIGINAL: GlennS

Check the speed / reference sensor. A symptom would be no "bounce" from the rev counter when cranking.

Thanks - but the rev counter does bounce when I crank. Is that conclusive?

Well.... not conclusive. It could be giving a signal but not a good enough one to make the ECU happy. Lack of bounce is conclusive that you have a problem. There is a test process defined in the workshop manual if you want to be definitive about it working. If you're seeing bounce, though, I'd be inclined to look elsewhere first.

 

[nick9one1]

Ok, like you say I will investigate other possibilities and if I make no progress I'll come back to this.

 

[Dunners]

Check all hoses - especially ones for your idle control valve.

I had a crack in mine that was causing issues.

 

[zcacogp]

My S2 did something similar when driving 'round France 18 months or so ago, although was noticably much worse on hot starting. I wondered whether it was due to fuel vapourisation in the injector manifold, and discovered that taking the cover off helped a lot.

I never did get to the bottom of it as the car has behaved itself perfectly since getting off the ferry in Dover! (Maybe it just doesn't like the French. Actually, that's pretty likely ... )


Oli.

 

[os951]

Most likely hall-sensor at flywheel causes this. (16 V models have only one sensor there compared to older Motronic version on 8V models which have two sensors). Check also cam sensor. Car runs without it, but if there is a malfunction in it, it causes starting problems as well.

 

[nick9one1]

Finally changed the O2 sensor on Saturday - what a pig of a job!

The old one was seized solid so I had no option but to take the center section out and try to remove it while it was off the car.
Once off the car I managed to turn it about 90 degrees before it sheared. The thread was completely bonded and I had no chance of removing it.
Fortunately I had a new and unused O2 boss designed to be welded into the exhaust, so I welded a plate over the old one, drilled a hole and welded the new one in.

Then I got thinking, the O2 doesn't come into the picture until its warm (8 seconds for the ones with heater wires - so I've read). So its very unlikely it would make a difference to starting. But nevermind, It probably needed a new one anyway!

Now Ive driven it for a few days, I think my mpg has improved, and idle is very very stable. It sits at 900rpm and you can hardly see the needle moving!

 

[peanut]

have you checked the fuel pressure yet ? and also the fuel pressure leakdown time?( the details are in a guide on Clarkes garage workshop guide.)

Hard starting and high idle can sometimes be caused by both over and under-pressure fuel delivery.

Try disconnecting one of the injector electrical connectors and starting the car. if it starts more readily it could indicate an over-fueling situation caused by a leaky injector or a stuck FPR valve.

The FPR stuck open could also cause a low fuel pressure situation which will effect starting but not necesarily running.

It would help a lot to clean all your earths and ignition electrical connections to improve the odds. Poor contacts and high resistance connections are often worse in damp . conditions