LH-SFI 4.1 - Self adaption idle air?
 

My R129 '93 has no O2 sensors and no Cat and therefore I wonder how the self adaption works. How can the car adapt to air leaks etc over it's life if it cannot measure them - or can it somehow?

No O2 sensors threw me for a while because by using a scanner I can see O2 real time data from the LH module, but I suspect that this figure is mapped - is this correct? Does the LH module 'inject' the signal fooling the LH software into thinking it's got O2 sensors?

Back to self adaption.....if the car cannot sense the actual real air/fuel ratio at the exhaust manifold, how can it learn? Perhaps this signal is also mapped against time?

I'm pondering this as I believe my car is running weak CO = 0.15 (remember no Cat) and she suffers from a little surging when really cold - which can be made worse when I pull a pipe to inject more air.

Any thoughts?

I doubt that it does a mixture adaptation if there is no feedback sensor = O2 sensor.

It will still adapt to intake air at idle because air is not controlled for mixture it is controlled for engine speed. It is monitoring speed though, so the initial setting for idle air amount can be adapted to account for varying air leaks as they affect idle speed not mixture directly. Of course if you have air leaking in and the throttling device is adapting to shut it off you gain a larger portion of unmetered air so that a system that is not in feedback control of fuel will get leaner and leaner.

Hope that makes sense.

That makes sense and would explain why when I press the accelerator just a fraction, the surging stops immediately - as you explained due to the ratio of metered to unmetered air.

I would like to learn how to interpret the real time data available from the LH module (including data such as 'self adaption idle air' etc) therefore can you recommend any training material/books/web sites?

I already have 'Bosch Fuel Injection & Engine Management' by Charles O Probst, whilst a superb book for beginners, It doesn't explorer engine diagnostics to any great detail - I would be most grateful.


Cheers
Lea

Most Probably
 

A false O2 sensor signal is being generated and injected into the O2 port. A 555 timer would do a good job.

I don't really know of any training except for some hibuck professional stuff.

The best book I know would be the DM in print (Diagnostic Manual). I'm not sure MB provides this anymore in print as it is available on their WIS system and the pay by day tech site www.startekinfo.com . I could teach you a six month course from the info available on that site. I'm not sure but you probably could download the DM engines Volumes 1-4 and have it all.

Also available would be the theory of operation section in the WIS section, wiring diagrams, vacuum diagrams, etc., etc..

The DM tells a lot of things but most importantly its tells the enabling criteria for the fault codes you will read. This means it tells you what conditions make the action and from there the testing that is physically needed: scope testing a circuit, verifying an action, whatever.

In the long run you will need ultimate understanding of the workings and strategy used by the system to understand the diagnostic strategy used to put it right.

PS: The DM originally was sold in print in loose left updatable binders that have to be assembled from their parts if still available. There are 15-20 of them, about five feet on a shelf. They are about systems, not models, but are divided into each models application of each system. Such as in the case of LH it woul include the 104 motor and the 120 motor also and only have footnotes as to how the system might be different in a 129, 140, 124 body.

I haven't seen them on ebay, but I haven't been looking. If you could get DM- Engines Vol 2 and 3 you would be covered for LH, the whole 4th Vol is ME. The last models I saw in print were 1997. There is more coverage than that on WIS and Startek.

Steve

Many here, including yourself, have pointed to the Star Tek site but for us mere English types it isn't quite so easy - and the daily charge is prohibitive for DIY users! Also I notice that it mentions '94 onwards - I'm a '93 :(

However, if I can subscribe for just a day and download the DMs that you mention it might make it well worth it? I wonder if this is even possible as there would need to be a 'save as' option and the files in PDF or similar.

Maybe someone with access could let me know - or ever better download them ;) :cool:


wbain5280

Do you know where from? The base module perhaps, or somewhere else? I have no O2 ports in my manifold and therefore know it cannot be there.

ah, the good old favourite - everyone loves a 555 :D

I have downloaded a number of files there and most were pdfs.

I downloaded wiring diagrams in color one time and either couldn't find how again or it was changed the next time. I'm not currently subscribed to startek so I can't look it up for you. Besides, if you wish to work on these cars you need to know what is bottom line. If you could you should sopend a day seeing how it can help you.

I don't think you can get on as they require a US address on the Mastercard billing address. I know a tech in Australia that gets on the BMW site by having a friend in LA pay the bill.

Steve

Again, I'm astounded by your enthusiasm, response time, and support that you give this forum - StarTek doesn't come close to this level of service.

I have several friends based in the US and so I'm sure I could come to an agreement with one of them ;) And especially as there's 1.89UKP/Dollar I should invest in a Sunday's reading/downloading ....


Cheers
Lea