Jetronic

[drew@dyermaker.cs.uoguelph.ca (drew)]

The system being referred to here is CIS with lambda feedback, or
k-lambda jetronic I think is it's bosch label?

In Canada this syetm saw its debut on GTI, GLI, Cab and Sciroccos with the
1.8L JH motor.  These were the first cat-equipped A chassis VW's sold in
this country.

The mechanical components of the system are identical to CIS with the
exception of the addition of an electronically controlled valve to adjust
fuel pressure (and therefore fuel mixture) based on the signal provided to
the control module (or computer) by the O2 sensor.

Electrically there is an O2 sensor, a coolant switch (to indicate cold
engine condition) and a full throttle switch  that provide
feedback to the control module.  The control module in turn modulates the
valve on the fuel distributor.  All other CIS components (control pressure
regulator (warmup regulator), cold start injector (5th injector), and
auxillary air bypass operate identically to a straight CIS system and are
not controlled by the control unit.

Besides having the benefit of better driveability, emissions and economy,
the Cis-lambda system on the JH has a full throttle enrichment switch
which improves full throttle performance - something lacking in a straight
CIS system.

Typically the O2 sensor on these systems gets lazy and requires
replacement, but other than that they generally do not require any
maintenance (other than keeping the electrical connectors and ground clean
and tight.)

All in all, it's a simple, reliable design, and if it's functioning
correctly, there's no reason to remove it.

I'm actually considering retrofitting the system to my straight CIS 87
Jetta, which I feel could benefit from some full-throttle enrichment.

Hope this helps,

Drew

On Fri, 21 Jun 2002, Jeff Smith wrote:

> 
>  Bosch Jetronic was used in literally millions of cars from the late 70s thru the mid 80s.  It's not just used in VWs, but Mercedes-Benz, BMW, Porsche, and many other European auto makers.  Like any computer, it can go bad, but no more of a chance than any other.  Removing the system means you'll need new a Engine Management system or a conversion to carbs.  Either was is way more expensive than just leaving the stock Jetronic system.
> Jeff
>   Elyse & Andy Lecharrois <ealecharrois@shaw.ca> wrote: I'm looking at an almost mint '84 (original owner, 134k), it has the
> Jetronic computer in it. I have heard alot of bad stuff about them. Is it
> possible to remove and how hard is it. Would I have to rewire a lot of
> components? I'm going to leave it if I decide to buy this car until
> something goes wrong with it. Was Jetronic supposed to be a better fuel
> management system?
> 
> Andy
> 
> 
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Drew MacPherson - '84 Wolfsburg Edition Scirocco TurboDiesel