My M20B23 struggles to idle when cold...fine once warm

[poolnoodle]

Hi All,
My M20B23 has developed a strange fault recently. It really struggles to idle when cold - sitting around 500-600rpm and occasionally cutting out.

The car runs fine once warm and I have noticed no other issues.

I don't get to drive it very often and leading up to this problem (hadn't driven the car for a couple of weeks) it was running perfectly...

Any suggestions on a starting point for diagnosis would be much appreciated.

[Grrrmachine]

Bad Idle is a particular problem of the M20 engine. You can work through the Wiki link and report back:

http://www.e30zone.net/e30zonewiki/inde ... ake#Idling

[sweep]

Water controled idle valve?

[poolnoodle]

Thanks all, have had a bit of a look around in conjunction with my manual (heaven forbid) and think I will start with a clean of the cold start valve.

Note that the car has L-Jetronic injection (very early model) which seems to have a slightly different cold start arrangement. The manual refers to the "7th injector" as the cold start mechanism

[kyland]

I think you'll find there is no 7th injector on the L-Jet if it's the same as my '85 323i.

As previously mentioned, I'd look at the air slide valve (water controlled valve) under the inlet manifold. It has 2 coolant pipes and 2 air piped attached to it.

It is meant to open when cold, and close when fully warmed up. If this is stuck closed, your cold idle will be crap, but ok when warm.

[B7]

Pool

I have these from a perfect working car for sale if you want to replace. not sure what postage would be but drop me a PM if interested.

Honestly, the car ran like a watch. It was a 1987 320i four door, chassis number 0509638 if you want to cross check part numbers.


By b7tmw at 2012-06-03

By b7tmw at 2012-06-03

[poolnoodle]

Thanks for the advice and offers guys. I have a good supply of parts locally so that isn't an issue. Will check a few things next weekend - nights are too cold in the shed at this time of year brrr
It seems that very early E30s (mine is 10/83) essentially have an E21 engine

[pacerpete]

Thanks for the advice and offers guys. I have a good supply of parts locally so that isn't an issue. Will check a few things next weekend - nights are too cold in the shed at this time of year brrr
It seems that very early E30s (mine is 10/83) essentially have an E21 engine

E21 engine is VERY different, it is K jet ! Early E30 320 and 323 are similar.

When you have sorted the cold start issue, be sure to check the ignition timing, most are set incorrectly costing power and fuel

[poolnoodle]

E21 engine is VERY different, it is K jet ! Early E30 320 and 323 are similar

How would I tell if I have a K or L jet engine.
Here is a pic if that helps:

[kyland]

Poolnoodle,

From the photos, yours is definately L-Jet. There is 2 versions of L-Jet, and yours appears to be the earlier version, as you do have the cold-start injector (mounted on the drivers side above the rocker cover. You can see the blue connector and the fuel line in the second photo).

Try checking that when cold, the injector is working. Also check the temp sender as this triggers the injector below a certain temperature.

I found the Bentley useless for our engines as it doesn't cover L-Jet, so try an E21 manual?

[Speedtouch]

Yes, a 323i will be analogue L-Jetronic. As said above, most likely to be the water-heated slide valve that's stuck - a very common problem with these.

I had a 1987 320iSE that had the problem, but that would idle too high (1,500 rpm+) when cold.

[poolnoodle]

Yes, a 323i will be analogue L-Jetronic. As said above, most likely to be the water-heated slide valve that's stuck - a very common problem with these.

I had a 1987 320iSE that had the problem, but that would idle too high (1,500 rpm+) when cold.

Finally back to this...been to busy to even look at the car, let alone drive it


Now please be patient with a novice mechanic but...
How do I remove and check the water heated slide valve? It seems almost inaccessible - do I need to remove the inlet manifold.

What about the cold start valve (the mythical 7th injector)?

Mr Bentley doesn seem much help

[Speedtouch]

It looks easy enough from this thread - just held on by two small bolts:

http://www.e30tech.com/forum/showthread.php?t=98014

[hennabm]

It is held onto a bracket under the inlet manifold on two rubber mounts.

Connected to it are two vacuum pipes and two water pipes to disconnect.

Once removed then the way to check the operation is to get it under running hot water and notice if the slider inside actually moves. Obviously if it doesn't then a replacement is needed. IIRC you can't take them apart to clean.

I did have a spare but someone with a moredoor (now scrapped) took it and and didn't return it, otherwise I would be able to supply a good one.

The so called 7th injector (cold start injector) is on the drivers side of the manifold. It is clearly seen in the photo above with an electrical connection andfuel pipe connected to it.


BTW yours is definitely L jet like mine!


HTH

[poolnoodle]

Thanks guys, that's great. So is the valve likely to be fubar or just sticking? I rarely drive the car (only about 1000km in last 12 months) and hadn't driven if for quite some time prior to it playing up.

Day off work tomorrow so will hopefully get it sorted

[pacerpete]

It is held onto a bracket under the inlet manifold on two rubber mounts.

Connected to it are two vacuum pipes and two water pipes to disconnect.

Once removed then the way to check the operation is to get it under running hot water and notice if the slider inside actually moves. Obviously if it doesn't then a replacement is needed. IIRC you can't take them apart to clean.

I did have a spare but someone with a moredoor (now scrapped) took it and and didn't return it, otherwise I would be able to supply a good one.

The so called 7th injector (cold start injector) is on the drivers side of the manifold. It is clearly seen in the photo above with an electrical connection andfuel pipe connected to it.


BTW yours is definitely L jet like mine!


HTH

Don't talk to me about morally bankrupt moredoor types !

n a positive note, at least another quattroporte met its maker

[hennabm]

It could be just sticking. If so when running under the hot water try poking it to see if it will move.
If so it might be worth trying to free it off.

IIRC they are NLA from BMW. Sorry.

[Andyboy]

The cold start injector is on the manifold with the blue bit. The idle H valves are normally shagged so you'll probably need a new one. But first check that hot coolant is getting to the valve - often, the coolant take off is blocked with alloy corrosion. It's a horrible system.

[Speedtouch]

No worse than most other cars of the late '70s/early '80s. My Fiat twin-cam's Weber carb has a water heated bi-metallic automatic choke, which for the most part works OK, but occasionally plays up and can take an age to fully open the choke, which is of course, pretty cr@p if you're only using the car for short journeys.

[poolnoodle]

Thanks for all the advice guys.
I have a month of holidays (see Pub Talk section - first child just born ) and want to tidy up some jobs.
I am pretty certain it is the slide valve and wanted to check a few things:

1. Are they normally cactus or just seized up?

2. It looks a bit tricky to reach for removal - is there anything I should know ie. easier to remove throttle body, etc

3. Best way to test - I assume in a pot of water on the stove top?


Any tips most welcome

TIA
Neal

[poolnoodle]

I have managed to un-sieze ones before by soaking them in paraffin and then working the piston till it frees up.

Not difficult to remove, just bit awkward as it is buried under the manifold making getting to the hose clamps tricky. Spray each hose clamp with a light oil before attempting to undo them. It is held on by a bracket with 10mm nut/bolt heads.

Put in water and heat up while watching the piston. It should close up as it gets hotter.

If yours is toast, I probably have a good one squirreled away here somewhere.

Thanks Will. I note a new one won't leave me much change from $200

[poolnoodle]

OK, finally got a chance to pull the slide valve today and this is what I found:


A small strip of rubber protruding from the port and stuck in place:?
Is this something that has come through system and lodged in slide or is it part of the valve and is cactus?
Do I dismantle the valve and clean?
Help please

[Speedtouch]

I would strip it down and see what's what - it's probably not that complicated.

At least it appears externally to be in fair condition, so should come apart quite easily.

[poolnoodle]

Have split the valve into two halves - should it break down any further?
Piston does not seem to move but didn't want to force anything. A small actuating rod between the two halves seems to move OK.
Any help appreciated

[kyland]

If it's not blocked with crap or corrosion, I'd say it FUBAR....time for a new one unfortunately.

[Speedtouch]

Try the hot water test of pouring very hot water into the coolant passage to see if the air valve closes off.

If the valve won't budge, you could try leaving it for a day or two in diesel or similar penetrating oil.

[poolnoodle]

Thanks for the assistance guys - I got it working again.
A win for the barely competent home mechanic

A soak in Yield follow by a little grease in the bore and then gentle persuasion of the piston with a dowel and small hammer got it going. Pushed it in and out a few times and it started was moving nice and freely.
A test in boiling water confirmed my success.

Car started and ran beautifully first time...good feeling that (particularly the saving of a few hundred dollars)

As always, this site proves invaluable with good advice, suggestions and some confidence to proceed.

Thanks again - particular Willnz and Speedtouch, you guys get a beer when you are in Hobart

Now for a fruity E34 fuel gauge

[Speedtouch]

Well done, must be a good feeling.

I had one go on a 1987 320iSE - it idled at 1200-1500rpm, despite adjusting the idle stop screw. I sold it before becoming aware of what the issue may have been.

[Andyboy]

OK, finally got a chance to pull the slide valve today and this is what I found:


A small strip of rubber protruding from the port and stuck in place:?
Is this something that has come through system and lodged in slide or is it part of the valve and is cactus?
Do I dismantle the valve and clean?
Help please

I've never seen one like that. Most of these are sealed units so perhaps the Aus spec cars have something different?

[poolnoodle]

Age related difference - it's a very early model