Now things get a bit more interesting!
Coincidentally, last week while collecting parts I got chatting with a very experienced Alfa mechanic. When I described this symptom (2.0lt JTS engine) he recognised it instantly.
It’s not a case for re-mapping although doubtless it could be resolved that way. Apparently Alfa where aware of this, caused by excessive resistance in the connector between engine wiring harness and Lambda sensors, the two pre-cat wide band lambda sensors in this case. A quality issue with the socket on the connector (female side on engine harness) gradually causes a build up of resistance, cleaning might not resolve as it’s an issue with type of metal coating used on the pins.
The ECU & software are designed to be very sensitive (possibly too sensitive) to the rapid switching which occurs at this particular rev range (see extract press release by Italiancar.net below describing lean burn JTS) Alfa where originally replacing the two wide band Lambda sensors as a fix however, my helpful mechanic told me simply to cut the connector (engine harness end) and solder each wire to its corresponding (male) pin on the Lambda sensor plug. Then carefully protect each wire with “heat-shrink” tubing to complete the repair.
Low speed hesitation can be attributed to many other faults; air leaks, contaminated throttle body, PCV leaks, coil faults to name just a few! So there’s not guarantee this would solve all cases of hesitation.
My first action will be to carefully clean (using electronic switch cleaner) all Lambda connections….yes I know what I’ve just said above but currently I don’t have time to butcher the wiring. In truth there’s a list of more serious (annoying) faults to fix first!
Let you know if how this goes
“It goes without saying that Alfa Romeo's approach to the new technology had to be quite different. Category-topping performance and irrepressible driving behaviour have always been essential requirements for all Alfa Romeo models. But what was to stop Alfa Romeo from using direct injection to increase engine power and torque in keeping with the sporty applications of this technology? Then, Alfa's engineers reasoned, the stratified charge system could be brought in to reduce fuel consumption within a restricted rpm band around idle speed. The result was an entirely original Alfa Romeo approach to applying direct injection in petrol engines. A solution that offered a compromise between the two methods pursued to date.
The New Alfa 156 2.0 JTS works using a lean burn approach up to around 1500 rpm and this saves fuel, although not as much as on other lean petrol direct injection engines. Above this rpm, the engine burns a stoichiometric air-fuel mixture, i.e. with a normal 14.7:1 ratio between both components. All this means outstanding performance. This is much better than would be obtained using a normal indirect injection petrol unit”