Missing mystery valve in M20B23 vacuum line..

[bloodsnot]

Gentlemen,

I've got an '85 323i that is missing a valve that RealOEM diagrams indicate should be in the middle of one of the vacuum lines running between the distributor and the throttle body. See the diagram below (note that the setup on the left side is from pre 2/83 cars):

The tables that accompany it (link to RealOEM page) indicate that in cars made from 9/84 and on, the lines should follow the route through the valve labeled as #16 in the diagram instead of #12.

The problem is that, on my car, both of the small vacuum lines running between the distributor and the throttle body (called out as #'s 7 and 11 as they leave the TB in that diagram) connect directly with nothing plumbed inline! Does anyone know what this missing valve does or what it's called?!

Every google result I can get using the part number (11731705584) that's in English doesn't offer any further explanation than that. I can't seem to find them for sale anywhere, either.. so hopefully it's not critical..?

Any input is appreciated. Thanks in advance

[Jim320i]

Which number in the picture is it you are missing? 16 or 12?

Might just be me, but I cant figure out which you are referring to

[daimlerman]

I'm wondering if it's an emmisions control valve of some sort,would not have been fitted to UK spec cars,possibly only for California bound cars in early '80's.

Knowledge on these early systems is limited, possible zoners who may have information would be pacerpete,e30topless or andyboy.

But as Jim writes,knowing just which bit will help!

[Andyboy]

It's a vacuum damper and an 85 car may not have it, especially an auto. Metal or plastic airbox?

[Brianmoooore]

When you use RealOEM, put the VIN of YOUR car (last 7 digits) into the search box.
The same diagram will come up, but ONLY the parts that appear in the list below the diagram are fitted.

[bloodsnot]

Which number in the picture is it you are missing? 16 or 12?

Might just be me, but I cant figure out which you are referring to

Sorry that I was vague about which one I'm missing - I had been breathing carb cleaner fumes for a few hours before posting... It wasn't in the same paragraph but I did state that my car is an '85 and as such I'm missing #16, being as all '85 cars were made post 9/84. I'll try to be more clear in the future.

I'm wondering if it's an emmisions control valve of some sort,would not have been fitted to UK spec cars,possibly only for California bound cars in early '80's.

Knowledge on these early systems is limited, possible zoners who may have information would be pacerpete,e30topless or andyboy.

But as Jim writes,knowing just which bit will help!

Here is where I definitely should've been more specific. This is a German language continental European model that was grey-market imported to the US state of Washington sometime in the 90's. It definitely wasn't a California-bound car from the factory so maybe it never had one of these? If those users you mentioned don't randomly happen upon this thread and chime in, perhaps I'll start sending some PMs.

It's a vacuum damper and an 85 car may not have it, especially an auto. Metal or plastic airbox?

Thanks Andyboy. What function would this vacuum damper serve between the distributor and the TB?

The car is a 5-speed manual. It had an aftermarket K&N air intake on it when I purchased it last year so I don't know which airbox it came with originally. Are the metal/plastic versions specific to the transmission?

When you use RealOEM, put the VIN of YOUR car (last 7 digits) into the search box.
The same diagram will come up, but ONLY the parts that appear in the list below the diagram are fitted.

Thanks Brian. I have always been using my VIN for RealOEM but didn't know that selectively displaying your parts was a benefit of using the VIN; I had thought that it just found the right diagrams. In fact, a long time ago I bookmarked the RealOEM page that came up after entering my VIN so I wouldn't have to do it every time. What I didn't realize was that the browser cookie was storing the VIN and would alter the parts lists. The URL that my bookmark pointed to just brought up the right diagrams.

So, if the cookie gets cleared and you use the bookmarked search it does bring up the right diagrams but with the entire parts list for all years of E30 323i models. I was having to do a lot of sifting through the production dates. I've corrected this problem by adding the RealOEM cookie to my brower's security whitelist so the cookie no longer gets cleared when I close out of the program.

When I do a VIN-specific search on RealOEM, this valve (#16 in the diagram) does still come up...

Anyways. Thanks all for your input! I really appreciate you blokes helping me out.

[Andyboy]

The damper is there go damp the vacuum retard system on the overrun. Later cars did without it so if your car runs okay, forget about it.

[bloodsnot]

The damper is there go damp the vacuum retard system on the overrun. Later cars did without it so if your car runs okay, forget about it.

Well, the reason I discovered this was missing was because I was taking out the TPS to clean and test it because the car doesn't really run okay

What would the symptoms be of undamped vacuum retard on overrun?

My TPS was suspect because I'm suffering from awful fuel economy and some poor cold-running issues. Don't know if missing this valve would be related so I guess I'll run without it for the time being..

Thanks again, Andyboy.

[gazwhittle]

Check and change the coolant temp sensor which I what I'm doing this morning on my 85 323 engine. Mine also has that valve missing and never really caused me any problems tbh.

The sensor is £10 from general traffic worth changing to Eliminate the problem I'm hoping it will help with my poor fuel economy.

[Grrrmachine]

It's probably worth having a read of this page so that you can see all the quirks of the Jetronic setup:v

http://www.e30zone.net/e30zonewiki/index.php/Jetronic

[Andyboy]

The damper is there go damp the vacuum retard system on the overrun. Later cars did without it so if your car runs okay, forget about it.

Well, the reason I discovered this was missing was because I was taking out the TPS to clean and test it because the car doesn't really run okay

What would the symptoms be of undamped vacuum retard on overrun?

My TPS was suspect because I'm suffering from awful fuel economy and some poor cold-running issues. Don't know if missing this valve would be related so I guess I'll run without it for the time being..

Thanks again, Andyboy.

Try it without the vacuum rertard connected. Automatics don't have it at all. The TPS needs to be set up so you hear the click as you open the throttle. It will be full of old engine oil so it wants removing, tghe outer casing opening up and washing out with petrol or carb/brake cleaner. Refit it and set it up so you hear the click just as the throttle opens. Some raise the idle speed on the throttle screw - a big no-no because you then have the engine idling on the part load maps - savage fuel consumption, sooty plugs etc.
These old LE Jetronic cars need a day spent taking things apart, cleaning and adjusting.

[bloodsnot]

Check and change the coolant temp sensor which I what I'm doing this morning on my 85 323 engine. Mine also has that valve missing and never really caused me any problems tbh.

The sensor is £10 from general traffic worth changing to Eliminate the problem I'm hoping it will help with my poor fuel economy.

Already have a new CTS on my work bench and will install it while I'm putting the TB back on
And thanks for the input on yours not having that valve - that lends me some piece of mind. What year is your car?

It's probably worth having a read of this page so that you can see all the quirks of the Jetronic setup:v

Thanks! I'll definitely give it a read. The Jetronic stuff is even more of a pain over here in the states where (mostly) every other E30 is Motronic!

[bloodsnot]

Try it without the vacuum rertard connected. Automatics don't have it at all.

Thanks again, mate. Of the two vacuum lines running between the distributor and the TB - which is retard? I'm assuming it's #11 on that diagram from my original post (the one that would have this mystery valve in it). I'm sorry that I'm a bit thick on distributors and how they work.. most of my tinkering has been with distributorless ignition setups up prior to taking the E30 plunge!

The TPS needs to be set up so you hear the click as you open the throttle. It will be full of old engine oil so it wants removing, tghe outer casing opening up and washing out with petrol or carb/brake cleaner. Refit it and set it up so you hear the click just as the throttle opens.

I've just had a bit of fun with my TPS this past weekend. I cleaned out all of the oil and adjusted the fitment to hear the click right as the throttle opens. I even went so far as to test continuity on the correct prongs for WOT and closed throttle. Also, I drilled a tiny hole in the very lowest point of the housing so that the oil coming out of the valve cover breather into the throttle body won't pool down in the TPS housing any more.

Some raise the idle speed on the throttle screw - a big no-no because you then have the engine idling on the part load maps - savage fuel consumption, sooty plugs etc.
These old LE Jetronic cars need a day spent taking things apart, cleaning and adjusting.

When you say "throttle screw" are you referring to the screw that adjusts where the throttle linkage stops when the throttle cable is fully slackened for closed throttle? I've never messed with that.

However, I know of another idle adjustment screw but it's not on the TB or near the linkage at all; it's on the intake manifold. RealOEM shows it as #19 in this diagram:


I have toyed around with that before. I don't think this would cause idling on the part load maps (activated by the TPS). Could it have any other detrimental effects?

Thanks again for your input Andyboy. I very much appreciate it!

[Andyboy]

No.19 is where you should adjust the idle.

Quickest way of determining which is advance is to suck on the pipe. The engine speed will rise for advance and drop/stall for retard.

So much to check on these things. The water heated idle valve under the inlet manifold is a horrid thing. I'd be amazed if it still works.

[gazwhittle]

Mine is a 1985 316 with a 2.3 conversions which the engine came from a 1985 323.

Also if you have one check the cold start injector on the back of the inlet manifold it could be staying on when worm or be leaking.

I know early 323's have one but mine doesn't.

[bloodsnot]

No.19 is where you should adjust the idle.

Quickest way of determining which is advance is to suck on the pipe. The engine speed will rise for advance and drop/stall for retard.

So much to check on these things. The water heated idle valve under the inlet manifold is a horrid thing. I'd be amazed if it still works.

I'll try sucking on these lines when I get everything reassembled to see for myself which is which. Good thing I just replaced those two lines! No black lips for me

That additional air valve you mentioned was already under suspicion in my fuel economy caper. I've got it soaking in carb cleaner and will test it on the stove. Do you recommend any other way of servicing this thing? Seems to be a sealed unit...

Mine is a 1985 316 with a 2.3 conversions which the engine came from a 1985 323.

Also if you have one check the cold start injector on the back of the inlet manifold it could be staying on when worm or be leaking.

I know early 323's have one but mine doesn't.

Thanks for the input. Like yours, my engine is late enough such that it doesn't have the 7th injector on it. I know this because I couldn't find where to plug in the new on I had foolishly picked up earlier on in my attempts to solve my mileage woes