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Old 09-17-2012, 10:20 PM   #1
SubDad
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Air filter preferences? Car running rich thoughts?

I've got this European 1986 320i, 6 cylinder M20, L-Jetronic (See Sell or fix 325iS, or franken30? http://maxbimmer.com/forums/showthread.php?t=150503 ), it runs amazingly rich. Mapping is not possible on the L-Jetronic. The ECU that got this car running came out of Germany and may be expecting a CAT, something that this car left the factory without being as it was destined for Serbia. So maybe the lack of O2 sensor input has the ECU in some kind of warm-up mode at all times? Idle speed drops as engine temp climbs, temp sensor has good resistance. No intake leaks (would show lean anyway), good grounds, new plugs and distributor/rotor.

I've monkeyed with the idle mixture at the air flow sensor but idle still smells like gasoline and after a good drive the exhaust pipe is carbon black.
I'm starting to be suspicious of the cone shaped R*ct*v* air filter installed by one of the POs, gosh knows how long ago. Could it be choking?
I'd like to change it, even though it has no apparent defects, doesn't seem too dirty. I've got the factory airbox so I could go back to that but the cone filter sure makes a nice moan at WOT.

The cone filter has about the same surface area as the factory flat filter and I don't believe in miracles.

Any ideas? Anybody have opinions about air filters?
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Old 09-18-2012, 07:52 AM   #2
Dinanstu
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Its not the air filter.

Disconnect the MAF and see how it runs.

I would think lack of CATs, or more air flow, would create the opposite problem...
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Old 09-18-2012, 05:16 PM   #3
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Is it possible in any way that a chip is in this car or somebody monkied with a resistor inline with a temp sensor to force it to richen up thinking it was giving more power?

Is the dme look like it has been opened?

If that all rules out pull the rail put the injectors on securely and jump the fuel injector relay. Do the injectors leak?
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Old 09-18-2012, 08:23 PM   #4
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I like the leaking injector theory.

This car was parked for 8 months until I bought it and another 2 months before I found an ECU that worked. (From a junkyard in Germany - ordered on Sunday delivered on Friday via Canada Post: Wow. ).
I'm on the second tank of gas, into the first (old) one addded injector cleaner.

It's an L-Jetronic, the analog pre cursor to Motronic. It can't be chipped, there's no chip. It could have been opened, but it's held closed by rolled rivets and didn't seem to me have been opened when I installed it, but I didn't check that closely.
I disconnected the MAF (which is actually a VAF, Vane Air Flow sensor, apparently, http://www.diycardoctor.com/how_the_...nsor_works.htm) and because the system has no throttle position sensor it won't even start with no air sensor. It has two throttle switches, one each for WOT and closed throttle.
There's a vacuum pot that holds the throttle off closed except when the manifold vacuum is reduced rapidly. It probably would have started on the signal from the throttle closed switch if I'd held back the pot rod.

While doing that it occured to me (Duh!) that even if the air filter was completely clogged the volume or even mass of air would be reduced, and since the job of the M/VAF is to sense the actual air the air filter can't affect anything but max output.

Yes, I like the leaking injector theory. I suppose a set of really dirty injectors could do the same thing.
I need to think about the inline resistor idea. From the website above: "Inversely proportional systems (L-Jetronic) output a high voltage at idle with the voltage decreasing as air flow increases."

Hmmm.
Sorry for thinking out loud.
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Old 09-18-2012, 08:40 PM   #5
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While you're there check the fuel pressure regulator. bad reg could flood injectors.
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Old 09-18-2012, 08:52 PM   #6
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Good point.
The regulator looks new, but since parts for this car are hard to get maybe the PO put in the wrong one.
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Old 09-18-2012, 08:58 PM   #7
DR.ZED
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Pinched or restricted fuel return line can also drive up pressure past regulator. If I'm not mistaken regulator is after the rail on our cars.

You can t the line before the rail for a schrader valve to check pressure. I have a kit which you can use which has this special t And a gauge. I'm in Oshawa. Pm me if you are interested.
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Old 09-18-2012, 10:05 PM   #8
SubDad
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I think I know what you mean and the Schrader valve is a really good idea. Now why didn't I think of that?

Aside from a good gauge I have the stuff I need, thanks for the offer and for the idea.
I'll get on it on the weekend. I'll need a vacuum gauge too...
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Old 09-19-2012, 07:01 AM   #9
frankie591
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does jetronic allow you to read codes through a port or stomp test?
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Old 09-19-2012, 05:27 PM   #10
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Quote:
Originally Posted by frankie591 View Post
does jetronic allow you to read codes through a port or stomp test?
Nope. It's purely analog.
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Old 09-19-2012, 05:54 PM   #11
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I didn't read through the hole post but the Allen screw in the mass air flow sensor have you adjusted it?
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Old 09-19-2012, 08:02 PM   #12
SubDad
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Shameful Plan

Yes, I wound the Allen plug 5 turns, then gave it another 2.
Not much change, but some.
It's interesting that when I bought the car there was an Allen key rattling around on the plug and the PO said that when he bought the car the Allen key was there so he just left it.

Now the plan. I'm so ashamed... please stop reading.
On Monday (which is my birthday) I'm going to drop the car off at a popular and expensive local BMW fixer. They're going to install the timing belt I bought last spring, measure the fuel pressure and check the timing. Then they can do the CO read that my favourite BMW restoration book says is so essential to adjusting that Allen plug.
Hey, it's my birthday... it's my birthday present, see?

I promise that I will continue to keep my hands dirty on this car. While they're doing all that house keeping I'm taking the day off and going to the junkyard for a ski-pass seatback, a spoiler and a real BMW radio.
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Old 09-19-2012, 08:19 PM   #13
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Hahahaha hey it happens some time man. I just got mine an it was extremely rich too. I turned the screw clock wise all the way and backed it of one full turn. Not blowing black smoke now when I rev her up. Will get the gas analyser on it some time this week and check the co. Hopefully you get yours running great!
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Old 09-19-2012, 08:38 PM   #14
SubDad
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All the way in then one turn back?
OK, what the heck, I'll try that.
I bet I have it so far out that 1, 4 or 9 turns makes no difference to the air path. But if I do what you did I take it to a known condition and start from there...better than merrily winding away hoping for a miracle.
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