320i High Idle/Surge Issue solved...almost.

[TheWolfman]

THE PAINFUL JOURNEY


After going somewhat round the bend trying to get to the bottom of my High Idle issue on a Pre-Facelift 320i BAUR with L-Jetronic injection system,I've finally cracked the nut....or got at least much closer to cracking that nut at the very least.

The Issue itself:




The motor would start and then surge upto around 3000 RPM and would stay there until the engine would warm up where the car would idle steadily at about 1500RPM.


The plethora of things I tried to solve it:

• Installed new Spark Plugs

• Installed new Fuel Filter

• Checked Coolant Temperature Sensor Functionality - checked both at the sensor end and at Jetronic EMS end and was all in spec

• Checked Air Flow Meter functionality - track seems functional and in spec, air temp sensor seems broken

• Checked Throttle Position Sensor Functionality - I had already restored this, but checked again and all was working correctly

• Made sure that the Idle Bypass valve on the AFM was set to factory spec as it had clearly previously been mucked about with

• Readjusted Valve Rocker Clearances - also done before but 5000 miles ago so readjusted them to spec

• Checked that the Idle Adjustment screw on the Manifold was set correctly

• Double checked Water Slide Valve/ Air Slide Valve / Idle Valve functionality - all functioning correctly Link to Air Slide Valve Thread

• Smoke tested Intake for vacauum leaks - one small leak found on breather hose rocker cover end which was rectifed

• Checked Throttle Cable adjustment was correct and not pulling on throttle at idle

• Checked Throttle stop screw was adjusted correctly and not keeping throttle open

• New Distributor Cap and Rotor Arm fitted - About time anyway - no real difference

All of the above resulted in a smoother running engine with a bit more grunt, which was to be expected, but to put it bluntly did nothing but sweet FA for my Idle Issue....


MOMENTS OF DISCOVERY



It was only when I was changing the Distributor cap that I noticed that the 'Vacuum Advance Diaphragm' only had one hose coming out of it and had a port with no hose attached to it, which seemed somewhat odd to me....it was then that I had the words from another thread of the ever wise 'BrianMoooore' ringing in my ear in a Yoda like manner:

"If an engine is turning at 1300 RPM, it must be getting enough air to let it do so".............

So the first thing I thought I would do is check if the vacuum advance diaphragm was actually working so I just got a bike pump and attached it to the vacuum port and removed the Distributor cap.I then applied some vacuum with the bike pump, and yes the timing advance was working correctly as you can see in the following video:



After confirmation that the Vacuum Timing advance was actually working I was certain that this un-hosed vacuum port must be at the bottom of the issue,I then got a bit of old tubing (not the right size,but would do the job) and connected it up to the manifold where the Fuel Pressure regulator vacuum hose usually goes .........and lo-and-behold dip-my-nuts-in-a-bowl of-spacedust I heard the sound of my engines rev's dropping by about 1500 RPM!!! In this video when I am clamping the hose to create vacuum because the hose is a little too big, I am not actually pinching-it-shut,hence when you see me clamp it you hear the rev's drop:



After this revelatory moment I checked out the OEM drawings for the vacuum system and the diagram appears to show a vacuum hose going from the un-hosed port to the throttle body via a valve.As I say,the hose and it turns out the valve are not present in my system:

So my vacuum system is basically like this:

For some reason my Throttle Body is slightly different from the one in the diagram as it has a right angled port and it had a grey rubber cap over it .... which I'm assuming isn't meant to be there and was put there by a previous owner for some reason only known to them:

THE LIGHT AT THE END OF A VERY LONG TUNNEL

So there we have it, after a LOT of head scratching I finally managed to get to the bottom of this very irritating problem and finally got the car to idle a lot closer to where it's meant to by attaching a hose from the Timing Advance mechanism up to where the Throttle Body port was capped off and all is finally hunky-flippin'-dory!!! .

The car is still a bit high at around 1100 Revs, but I'm sure I can knock the final few hundred spins off with some investigation into the fuel pressure and supply, as I've got an inkling the Fuel Pressure Regulator might be kaput .I also need to get the RPM verified as well though as I feel the Tach may be a little off in the lower range as the engine sounds kinda 'right'.

It has definitely been yet another hard lesson in learning not to expect every component to be correct and present or setup as intended as you're almost guaranteed every time that someone's been under the hood unceremoniously f'ing about!

Only question I have now is whether the missing valve is entirely necessary?Particularly as the cheapest one I can find is about £60...but at the same time i guess it wouldn't be in the drawings if it wasn't needed, and I'd also like the car to be at it's original intended spec, not sure my bank account feels the same though! It is somewhat hard to decipher from the OEM drawings what exactly is and isn't part of my model though, which doesn't make it easy....as ever!

Big thankyou for all who pitched in on this on my previous thread about this and particularly BIG big-up to Yoda....sorry, I mean Mr BrianMooooore!

[Cloggy Saint]

Well done for cracking it! I guess the valve is a basic non -return item. I don't know anything about L-Jetronic, there's some crazy stuff going on with that set up!

[TheWolfman]

Nice one.Yeah it's all quite bonkers on the L-Jet, all feels a bit like this!:

Re the valve, yeah I think it's a basic non-return jobby and probably necessary.The only thing is the documentation is a bit ambiguous regarding my particular flavour of 320...

[BristolE30]

Nice one mate, good bit of investigation work!

[paultv]

Good work dude, glad to hear you finaly got it sorted out, it's often difficult to trace things which are missing without having a car to compare things with and most the oem drawings are generic or confusing.

Well done and great perseverance!

Paul

[martauto]

Glad it`s all sorted mate and may I say one of the best documented threads I have ever read !!!


Mart.

[TheWolfman]

Thanks guy's, that's most kind o' you fellas!

Yeah, the OEM drawings don't make things easy when they're not really specific and their don't actually seem to be any that are actually specific for my Baur.Yes Paul, it would most definitely be easier if my next door neighbour had one in perfect condition as an example..that would be nice!

I'm thinking I might just stick a cheapo non-return valve on their for the meantime as they all basically do the same thing right??

Like i've said before, if my endeavours in anyway save someone else some serious brainache or provide any insight however small then it's all worthwhile I reckon,I have after all gained so much from the information posted here and all the help on offer, so bigup to all of you Zoners!

[Foe]

An outstanding effort!!!
And well documented

[Brianmoooore]

Very well done for getting to the bottom of it! Stick with the basics of how an engine actually works (to rev to 1300 RPM it needs air to do so), and you get there in the end, without throwing loads of money replacing things that have nothing wrong with them.
My experience of 30s with old fashioned distributors is severely limited, but I have had plenty of experience with other cars with carbs. and distributors, and all of those have made do with a single vacuum pipe from the inlet manifold/throttle to the vacuum advance on the distributor, with the other side of the diaphragm being open to the atmosphere.
The important pipe at the distributor end is the one that makes the timing advance when you suck on it, and I'm fairly sure that just fitting this pipe will do. The other pipe on the distributor must be left open, or with a open ended hose fitted if it's in danger of getting dirt in, and, of course, any open ports on the throttle body or inlet manifold must be blocked off.
On some cars there was a restrictor in the vacuum line to prevent 'overshoot' of the advance if the throttle was suddenly snapped shut so that the vacuum increased suddenly.

[TheWolfman]

Cheers Brian, thanks again for the help.Looks like you survived the arduous South of France then! That was the original setup, just one pipe going to throttle body and the other port left open to atmosphere, on the OEM drawings however it shows both ports being piped to throttle body (one via a non-return valve) when I unblocked the covered inlet on the throttle body and connected that to the spare port on the throttle body that was blocked off it solved the problem,nearly. Jetronic is all a bit chaotic but kinda makes sense in many ways when you get your head around it.

[detroit]

Okay, wow. This is insane. First off thank you so much for putting this thread out there. I'm from New Zealand and I'm looking at this thread because my e30 too, is missing that vacuum line. I noticed it whilst doing my timing belt. Although our cases are different, they both have the same root issue, my idle is a bit high, 1000-1200rpm when warm. And that's why I'm even looking to fix this "vacuum leak".

Anyway, this is insane to me because this is like looking at my car. I too, have the right-angled port, with you'll never guess a grey cap on it. I too, cannot find where this mystery valve is. So maybe this isn't some previous owner trickery? But I'd like to thank you for giving me some confidence, and not thinking I was going insane for looking at diagrams and it not making sense at all lmao.

So I think I'm just going to do what you did here and bypass the missing valve, or at least give it a shot.

[boiliebasher]

Wow! What a fantastic thread! Kudos to the OP as it's a great read

[flybynite]

Well having owned an L-Jetronic 323i for over 30 years, driven it for over a decade and rebuilt it several times I can feel your pain.

When the car does go back on the road the B23 along with its leaky vacuum pipes, problematic slide valve and piston slap will be stored in a corner of the workshop for posterity and a Motronic 1.3 system sympatheticaly plumbed in its place.

[Brianmoooore]

a Motronic 1.3 system sympatheticaly plumbed in its place.

An extremely good idea! Wolfman's last but one post is exactly how I think of the early E30 engine management systems.

[flybynite]

a Motronic 1.3 system sympatheticaly plumbed in its place.

An extremely good idea! Wolfman's last but one post is exactly how I think of the early E30 engine management systems.

This is mine exactly how it was parked up 22 years ago. I really don't fancy having a fight with it again. The idea will be to keep the Motronic bits as hidden as possible and use the old bits where we can like trying to squeeze everything through the old square plug into the body loom.

If it helps any poor soul with an L-Jetronic I do have some good hi-res photographs if needed as the engine is fairly unmolested (except for a couple of added bits) and is a bit of a time warp.

[detroit]

I did this to my car, and it also seems to have fixed my high idle. I had an idle around 1200-1500rpm, not it's around 800 when warm. Thank you!

[TheWolfman]

I did this to my car, and it also seems to have fixed my high idle. I had an idle around 1200-1500rpm, not it's around 800 when warm. Thank you!

Hi Detroit,

Glad this was of help to you and you managed to sort your idle out.Quite interesting though that you also had the angled port and grey cap which would leave one to believe that it was actually factory like that.It does seem that the particular setup we have doesn’t seem to have any documentation regarding it as I have NEVER come across any diagrams for this clearly rare setup.

One thing to also maybe note however is that if your revs are high it may be worth checking them and getting the actual RPM externally verified as your cluster may have been changed at somepoint and clusters designed for 4 pot M20’s will read high revs on a six pot M20.This is obviously pretty easy to hear however if you are used to what engines sound like.

[TheWolfman]

a Motronic 1.3 system sympatheticaly plumbed in its place.

An extremely good idea! Wolfman's last but one post is exactly how I think of the early E30 engine management systems.

This is mine exactly how it was parked up 22 years ago. I really don't fancy having a fight with it again. The idea will be to keep the Motronic bits as hidden as possible and use the old bits where we can like trying to squeeze everything through the old square plug into the body loom.


IMG_1533 - Copy1.JPG

If it helps any poor soul with an L-Jetronic I do have some good hi-res photographs if needed as the engine is fairly unmolested (except for a couple of added bits) and is a bit of a time warp.

Bung those photos up dear sir!could be handy for sure.

[agisthos]

I too had high idle in my E30 323i Jetronic, and this was after replacing every vacuum hose and connecting it all up correctly. The cause was a leaking brake booster that was pulling air into the engine from the interior of the car footwell.

But the OP asked whether having that valve missing (part 16) between the distributor advance and the intake manifold will make any difference. I don't have a valve there either, I just have it straight connected. But I do have this part coming, and am interested to see what difference it makes.

[agisthos]

@flybynite please post your high rez pics of this engine bay. They are so rare to come across, making research hard.

[flybynite]

@flybynite please post your high rez pics of this engine bay. They are so rare to come across, making research hard.

Unfortunately photos do not come out hi-res on here (sensible so you don't get huge photos swamping the thread.

When I look at them they are not that clear, due to lighting and the 22 years of crap sitting on everything.

When I get back to see it again after all this chaos is over I will try to take some more but it may end up being when I get it back here to work on. I will document the strip down carefully if only for my own benefit should it go back to original.

[thesmugglaree]

I have the same rubber cap on my angled vacuum connection! Mine is a Swedish spec 323i -84. That rubber cap must be factory, the question is how all of the other ports were connected originally.