Re: ebugging the L-jetronic

[Godfrey DiGiorgi <ramarren@domain.elided>]

> Godfrey, The auxiliary air device should be wide open when the engine or
> ambient air is hot.  

Hmm. That sounds counter to what the fuel injection manuals imply. As I
understand it, the AAD allows additional airflow at startup/warmup time to
provide the high idle setting. I thought it closed as the engine and its
heating element warmed it up ... I'll have to look at the manual again.

The behavior at cold start time is like a fast idle valve is sticking and
then comes free: the idle is low and spluttery, it tries to die for a
moment, then it picks up and idles properly. This behavior is mapped in
the 1982 engine manual diagnostic chart. Everything else checks out
according to the tests outlined in the manual and on the IAP website
notes. That's why I think the AAD is at fault. Do you have a specific
procedure to test the operation of the AAD over its operating cycle?

> I am not a believer of simply substituting parts to see if things work
> better, save your money and test.  

Neither am I ... I like to first understand how things work, then test the
components to see if I find a failure, and then I do empirical testing if
I can't find anything wrong specifically by the testing. If the parts are
cheap enough or there are spares available, there's little to lose by
doing some empirical testing when other options don't pinpoint the cause
of a problem.

> What happens to air flow meters that stick is the jewelled bearings
> that support the valve which sticks in the upper portion of the unit.  
> Top bearing lets go and valve rubs up top.  Fred Di Matteo

There was a lot of corrosion on this engine/transmission when we pulled it
from the chassis, both externally and in the cylinders. Several bits of
the engine management system were dead by corrosion, including the
thermo-time sensor and one of the ignition pickups. Corrosion was
definitely a factor in the AFM as well. (The car sat in a barn and then in
a field in Pescadero (near the coast) for about two and a half years
before I got it, then in my garage from '94 on until the FrankenSpider
project started. Not the best way to store things. The '82 chassis was not
economically restorable due to all the corrosion on the underbody.)

It didn't operate smoothly when the engine first went together, but the
mechanic cleaned it up and it seemed to be functioning properly: the flap
valve seems to be operating the way it ought and the resistance readings
are on target. However, the replacement I put in last night works much
more effectively. So I feel there is some justification for empirical
testing when all else fails. 

Does anyone rebuild these AFMs? 

Do understand that the car is running very well now with the replaced AFM
and even the cold start "problem" is very minor ... more of a momentary
annoyance than anything else. I'm really just being fussy ... I believe it
should work better.

Godfrey

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