Motronic 4.1 newbie--fixed it!

[Putter C]

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Date: Tue, 16 Nov 1999 10:57:22 EST
From: "Derek Kaznoski" <sweetpea1998 at hotmail.com>
Subject: Motronic 4.1 newbie--fixed it!

I disconnected the battery, but this didn't help.

However, while inspecting the joints between the plenum and engine, I 
noticed a large 3mm gap at the first cylinder.  I repositioned the rubber 
sleeve and the car is running and idling again.  Needless to say I'm 
psyched!

My little mishap with the injector connector which caused the backfire was 
ironically my saving grace: the backfire blew the sleeve far enough out of 
place that even an idiot like me could see the gap.

After I repositioned it, I could no longer hear the hissing sound here.

I'm concerned, however, with the fact that the sleeve is spanning a gap of 
about 2 to 2.5 cm and just barely covers it.  It seems that the plenum 
chamber isn't close enough to the engine here.  Any tips on how to adjust 
the positioning of the plenum here?

The idle is still a tad low, but basically the same as when I purchased the 
car.  I think it would be better if the plenum were properly positioned, but

maybe not.  It just seems that malpositioning here would cause subtle 
airflow changes which could adversely affect performance.

Also, the AFM currently on the car is not the original.  The previous owner 
replaced the original with a refurbished one, but then found that the 
original wasn't bad after all.  I still have the original one.  The 
refurbished one feels much stiffer than the original, though still has 
smooth operation. The original one has noticably less resistance in its 
flapper opening.  Even after detensioning the spring by 3 notches in the 
refurbished one, it's still a lot tighter than the old one. Should I put 
this old one back on?  Would this improve idle/performance? (I know there is

a lot of debate over this)

Thanks,
Derek
'90 Alfa Spider


[CPutter]

Congrats.

As far as I know the Bosch units controlls the idle speed by means of a
electronic by-pass valve. The speed is sensed from the engine and is then
regulated to the specifically programmed value. In som of the bosch training
manuals that I have seen they specifically state that the idle speed is not
adjustable. (Maybe it is Hard-coded in the EPROM).

Another thisg you can check is if the by-pass valve is actually in
operation. Close down the by-pass hosse while the engine is ideling, if the
speed drops, and then when it is openned the speed goes higher than normal,
then the closed loop control is still in-tact. (On my astra i can close this
hose by pressing it with my thumb an finger, I do not know your set-up).

Cheers
Carlo Putter
Stellenbosch
South Africa