Slight run-on after turning the car off

Hi Paul,

Could be running rich, so leading to a little coking on the cylinder head which can cause run-on. Could also be wrong temperature plugs (too cool) getting coked. Pull the plugs and take a look. What are they like?

Consistent problem or only longer trips / hotter weather / similar variables? If so, timing slightly out?

in article snipped-for-privacy@uni-berlin.de, Grunff at snipped-for-privacy@ixxa.com wrote on

06/10/2004 21:08:

I have the NGK BCP7EV plugs, which are the cooler type. I'll pull them and take a look.

Paul

in article snipped-for-privacy@localhost.talkaboutautos.com, hippo at snipped-for-privacy@shoal.net.au wrote on 06/10/2004 23:16:

I tend to do only a couple of short trips a day, say 10 miles each. The slight run-on it when I shut the engine off is like a stumbling of the engine until it stops.

It doesn't seem to be a problem with the 97 RON (the engine seems to run a little hotter, if anything on that petrol - normal supermarket SUL), but the

98 RON Optimax has the idle running at about 1000 RPM, but the engine temperature definitely down a touch. I'll have a look at my spark plugs, as Grunff suggested.

Thanks,

Paul

in article snipped-for-privacy@uni-berlin.de, Grunff at snipped-for-privacy@ixxa.com wrote on

06/10/2004 21:08:

Okay, the sparks are fine - nice clear, slightly grey colour. I had a little trouble again with a warm start and I can smell petrol. Last time this happened, the fuel filter had got a hole ... I can't see anything immediate, but I'll check the road tomorrow morning for signs of leaking petrol. Why the f*** did SAAB move the fuel filter from the engine bay to under the rear wheel arch?

Assuming the fuel filter is okay, I presume it's an over-rich problem. I'll clean my air filter as well, since it seems to stutter a little when the throttle is tromped from idle. Dunno if that's petrol clearing through or whether I'm starved of air.

Paul

1989 900 Turbo S

Hehe..

I wouldn't be so sure. If it's running even slightly rich, you'd have black plugs - especially with them being BCP7EV.

It might even be running too lean, causing hot plugs & hot cyl head, leading to run-on. Know anyone with an exhaust analyser? he quickest way to tell. Either way, this is almost certainly a fuel mixture problem.

in article snipped-for-privacy@uni-berlin.de, Grunff at snipped-for-privacy@ixxa.com wrote on

07/10/2004 21:10:

Is it a big deal to "convert" it back to pre-'89 standard?

I have some BP6ES plugs with only a couple of thousand miles on them. Should I try those? I've been fine with the BCP7EVs before though.

The bane of the T8 :)

That would lead to a high warm idle, right? Say 1000-1100 RPM at times! Well, I've poked a 3mm allen key down the hole and can't get it to bite. It's a little dark, so I'll have another look in the morning. One of those Gunson things would be a good purchase for a CIS powered engine, I think :) I've squeezed the AAV pipes too, but that doesn't affect the idle so that's one thing ruled out at least.

It only seems to be a problem with Optimax. I've filled up on supermarket SUL since driving home this evening and it's kind of okay now, but not hitting the "high notes" turbo-wise that it did on Optimax. I'm inclined to try and adjust the mixture when I next get a tank of Optimax. There's no petrol on the road and I can't feel any around the fuel filter, so I think I'm okay there.

I'll see how it runs tomorrow ...

Thanks for your help,

Paul

1989 900 Turbo S

Since I've been running my 1983 900S (8V, n/a, auto) on 98, the idle speed with the transmission in P or N is noticably higher than when running on LRP. Doesn't seem to be a hassle except that the engine temp when idling is higher so the radiator fan cycles more often when the car is stationery for any extended period.

I'm going to check the timing now that I have a device to do that and then start checking if the idle speed needs to be re-adjusted due to the change of fuel.

Regards,

Craig.

I think the reason they did it was that under-bonnet space was getting scarce. If you have the space, I can't think of a reason not to change it back.

Not just yet.

Yes, running lean usually leads to higher warm idle.

I'd be inlcined to find a garage who will do an emissions test for a tenner. This will tell you much.

Good luck!

in article snipped-for-privacy@uni-berlin.de, Grunff at snipped-for-privacy@ixxa.com wrote on

08/10/2004 09:31:

... The fuel filter, that is :)

Erm, several start/stops today and each time was hard to fire up. I have actually found that the fuel filter (or unions) is leaking. I'll sort that out tomorrow ... Maybe do the conversion next time.

Paul

1989 900 Turbo S

in article BD8DC53A.12011% snipped-for-privacy@blueyonder.co.uk, Paul Halliday at snipped-for-privacy@blueyonder.co.uk wrote on 09/10/2004 16:41:

Hmmm ... Fixed. No run on ... No petrol smell ... No problem firing up ... It was a split line at the fuel filter end.

Everything is back to normal again now. I suppose the moral of the story is, check everything and when you jump to the wrong conclusion, check everything again! ... Or ask Grunff :)

Paul

1989 900 Turbo S

:-)

Glad it's sorted.