KU engine stalls slowing down when cold

[Ringmaster]

Will do.....

[ovalking]

I've experienced this stall issue on my KU engine 100, albeit probably about 6 journeys in the last 20 years! Most of the time it runs great.
I can relate to it happening when you slow down for a junction. Awkward in an automatic!
I had a theory it was something to do with the fuel cut-off but it was never persistent enough to troubleshoot properly.
I hate intermittent issues.

[AdrianH]

I had a load of trouble with the ISV in my MB, eventually cured when Pete R tracked down a new 'original' for me, the repros we tried were all rubbish. But I had improved the original one no end by putting the 'wet' end in a pot of carb cleaner for a few days and blowing out all the accumulated crud.

[Ringmaster]

It had its MOT on Wednesday and behaved impeccably.

These intermittent problems are a pain, but I am also guilty of not pampering it as much as I used to, so maybe it does just need a bit of fettling. I have to often remind myself it is 33 years old and apart from plugs and filters, it's all original.

When slowing down at a junction etc., I try to remember to keep one hand on the gear selector so I can slip it into neutral in case a stall threatens. That's one thing I like about the old 3 speed gearbox compared to many newer auto boxes. My daily e46 will only start in park and it doesn't like being put into neutral from drive..

[BackintheFold]

Originally Posted by BackintheFold

Thanks, I'll clean mine out and do the contacts too.

Just removed the valve. Tested operation with 9v battery and it worked fine. Cleaned it out with carb cleaner anyway, and also cleaned the contacts on the valve and the plug, and replaced it.

It’s certainly working now! With the valve in place and wired up the engine idles beautifully. When I unplug it, the revs drop down noticeably.

I’ll set it up properly another day, as I don’t have time tonight to run it up to temperature. I see it’s supposed to idle at 800rpm. Any ideas how to make it do that ? Current thoughts are to run it to temp, have the idle speed lower than it should be (so the isv does its job and brings the speed up) then taking that speed as my baseline, disconnecting the isv and setting the idle to the same speed by ear.
Then I can turn on all electrics and ensure the isv functions to bring revs back to normal.

I do have an old strobe light with a red led on it that works on 4 cylinder cars with a dial to indicate the revs—you turn a knob until the led comes on and the revs are written around the dial.
It’s not at all accurate, but I could use that as an indicator only-and ignore whatever revs the dial says it is on.

Sound sensible?

[BackintheFold]

I've bought a digital tacho gauge off Amzon for a tenner. A fly lead wraps round a spark plug lead and the unit shows the revs. Will be more accurate than the orange bars on the dash, and even if there is a problem with it being a 5 cylinder car (shouldn't be!), I can work out the revs from whatever reading it gives.

I can also get the ISV's current draw using my multimeter, so that will do me to set up the idle speed.

[Ringmaster]

On a slightly different note and probably more for engines with ECUs.....

I hear that if you do the following it should reset your engine's electronics (don't know what to make of it):

1. Disconnect both battery cables and hold them together.
2. Turn on the headlights to drain any remaining current.
3. Leave cables and headlights as they are for 15 minutes.
4. Reconnect cables.
5. Turn off lights.
6. Start engine.

Hopefully all is well at this point?....

[BackintheFold]

Without a specific statement from the manufacturer on that I would not short out my electrics on any car.
Disconnect the battery and leave it for a day then it can relearn parameters. But I wouldn’t short it.

[BackintheFold]

Originally Posted by BackintheFold

I've bought a digital tacho gauge off Amzon for a tenner. A fly lead wraps round a spark plug lead and the unit shows the revs. Will be more accurate than the orange bars on the dash, and even if there is a problem with it being a 5 cylinder car (shouldn't be!), I can work out the revs from whatever reading it gives.

I can also get the ISV's current draw using my multimeter, so that will do me to set up the idle speed.

Using my cheap Ebay digital tacho I wrapped the fly lead around the coil-dizzy wire, and at idle it read 4250. The Tacho has various settings for 2 stroke and 4 stroke and 1/2/4 cylinders. I don’t know what the setting was on, but 4250/5=850. Which is pretty darn good.

Later today I’m going to
Measure the current draw of the isv for good measure and will update this then.

UPDATE:The isv is drawing about 410mA, with the revs at 825. This suggests a slight mixture adjustment being required, but I do not have a co meter so I’ve left it as is.
If I increase the idle speed using the screw, the isv draws less current. The ideal draw is apparently 430mA at idle of 750-850, with a CO reading of 1.5%

825 is about as low as I like to go. The engine is still stable and not drawing too much petrol/warming up the engine bay at idle.