ECU problem?

Fri Apr 22, 2005 10:30 am

After I disconnect my battery for a few minutes, my car performes like never before, pulls hard, and really feels like I feel it should. After a few km's of driving it goes back to its "normal" slow self.
My mechanic said that it was because after the ECU is reset, it runs rich, and adapts. But I'm sure that an '84 323i doesn't have an o2 sensor, or really is smart enough to adapt to anything at all... :p

Anybody with any insight? If it is because of it running rich after an ECU reset, how do I make it run rich ALL THE TIME?

Mon Apr 25, 2005 10:58 am

*BUMP*
Somebody must know the answer to this one

Mon Apr 25, 2005 11:59 am

My 325 pulls harder than any of the others I've driven but the temperature gauge always thinks it's quite cold so maybe the choke's on and it's over-fueling? Or maybe I'm just lucky...

Mon Apr 25, 2005 12:15 pm

Im guessing here.. but dont replacement ECU chips just richen up the fuel curve a bit? And maybe advance the ignition slightly?

If this is true then this would kindof agree with your engine running richer and giving better acceleration.

just a thought.

Mon Apr 25, 2005 1:33 pm

Well my L-Jet doesn't touch ignition, so it has to be running rich.
However, I didn't think it could 'learn', as there is no o2 sensor to tell it if it's running rich/lean.

Cold motor + reset ECU = incredable low-rev pull
Cold motor + 'normal' ECU = nothing spesial

This has me kind of stumped, as L-Jet is quite a 'dumb' system, so there really shouldn't be that many variables.

I'm thinking of connecting an A/F ratio guage and an o2 sensor to see what really goes on...

Mon Apr 25, 2005 2:12 pm

To adjust the mix use an allen key in the hole on the top of the AFM, It might have a coloured plug covering the hole because your not meant to mess with it but just push a small screwdriver through it and pull it out.
Only adjust it by fractions of a turn at a time.
Clockwise/Rich, Anticlockwise/Lean.
(Keep an eye on the temperature after that)

Mon Apr 25, 2005 2:19 pm

Yeah, I've tried messing with that (have also tried it all the way rich)
It doesn't seem to do much at all. Nothing noticable anyway

Mon Apr 25, 2005 3:25 pm

Used to have a 323i and as far as I can remember, although the LJetronic only managed the fuel/air & temp it still had to relearn its programme after having power taken away. Mine always seemed to stall when I stopped while it was doing this and it seemed to take a few days before it really settled down. Temp sensor might be worth a check as you are losing power once it's warmed up and also make sure all the air/AFM components are clean. Stretching my memory really but might help.

Mon Apr 25, 2005 4:48 pm

Thanks for the tips

Mon Apr 25, 2005 5:10 pm

The mixture adjuster on the air flow meter only affects the mixture when the motor's idling, and could make your car fail its' MOT idle emissions test!!! - Doesn't have any affect during normal driving!

I think I read somewhere that you can adjust the actual spring tension on the flap inside the afm, perhaps someone else knows how to do this?

Also, have you checked to see if you've got any air leaks between the afm and the throttle body, or even around the inlet manifold (gaskets, vacuum pipes etc)? Could make your car run leaner than it's meant to.

Mon Apr 25, 2005 6:42 pm

jay528ise1985 wrote:The mixture adjuster on the air flow meter only affects the mixture when the motor's idling, and could make your car fail its' MOT idle emissions test!!! - Doesn't have any affect during normal driving!

Well, thats good to know, I thought there was something wrong since it wasn't having an effect. What are the effects of running too rich or lean at idle? Rich=soot and carbon deposits? What about lean?

jay528ise1985 wrote:I think I read somewhere that you can adjust the actual spring tension on the flap inside the afm, perhaps someone else knows how to do this?

Yeah I've heard about this as well, tighten the flap to get a richer mixture. But this sounds like a bad way to me, cutting back on airflow to increase the mixture... That flap seems restrictive enough as it is!

jay528ise1985 wrote: Also, have you checked to see if you've got any air leaks between the afm and the throttle body, or even around the inlet manifold (gaskets, vacuum pipes etc)? Could make your car run leaner than it's meant to.

I've searched high and low after vacum leaks, but I can't find any. Also, the car is not acting up in any other way to indicate a vacum leak.

Tue Apr 26, 2005 3:27 pm

I typed "jetronic+air+meter+spring" on Google and this site, amongst others came up:

http://www.viva-lancia.com/beta/ljet.html

As for idle mixture, most cars (pre-catatonic converter :lol:

)are set up to run slightly rich at idle as it tends to smooth the idle out. If idle mixture is too lean it runs like a pig and could overheat more easily so if I were you I'd go to your local garage and ask them to set your idle mixture/speed with the aid of their exhaust gas analyser!!!!

Tue Apr 26, 2005 7:26 pm

Thanks for the info, I've adjusted it 4 clicks the wrong way

I assumed that tighter spring = less air = richer mixture but all I've really done is make it even more restrictive.

It did seem to help a little though...

Wed Apr 27, 2005 2:47 pm

Tighter spring means flap moves LESS for a given volume of air and so will tell ECU to give less fuel. Totally different principle to carburettors!!!!

To get a richer mixture you want to slacken the spring so that the flap moves more at a given volume of air!

Thu Apr 28, 2005 9:45 am

Yeah, I'm used to carbs so I wasn't thinking strait

I'm thinking that my injectors are on the way out, and will be swapping them for bigger ones.

But... Are my stock 323i injectors "normal" High-Z og Low-Z like the eta?

Sat Aug 12, 2006 9:23 pm

323 are low imp( Z ) units, 3-5 ohms

325's and all motronic are high Z 14-16ohm units.