So, here's my problem: Step on the accelerator from a standing stop and the car goes, sort of stops, goes, and sort of stops. The car "bucks". The engine does not completely shut down. It does not happen when the car is moving at cruising speed.

My mechanic thinks its an electrical problem that occurs when the engine's initial torque causes the engine to shift and a fault is causing one side of the engine to lose electric power and the cylinders don't fire. But, he cannot find the offending component, wire, or connection.

Assuming he's right, does anyone have any suggestions where to look?

Assuming he's wrong, has anyone seen this before and if so, what was the fault and fix?

Many thanks in advance.

 

It is more or less two six cylinders arranged side by side. First thing to check, being marelli ignition is that you do not have a classic "Marelli failure".
If it only happens as you describe a good place to start would be the harness across the front of engine over to the two modules on top of radiator. Possible a fracture in that wiring is only coming into play with engine movement. You could also try disturbing the entire ignition harness bit by bit with the engine running.

 

Hi mnovet

Does this happen all the time? As I had a similar issue but only when the car was warming up. In some cases I would have to give the throttle a blip to stop it from stalling and for the first couple of minutes driving, power would be inconsistent.

Although I'm not convinced I've completely solved it. In my case the throttle body return spring needed cleaning as the throttle wasn't completely closing which ment the micro switch that should engage at idle didn't. It also ment i had an air/fuel mix at cold or idle that was not right, causing the engine ecu to try and overcompensate and cause all sorts of slightly odd occurrences.

 

It started recently and I brought right to my mechanic. I have not tried all variations.

 

Fuel starvation but not a total blockage.
Fuel is getting through but it is being restricted.
From experience I only noticed lack of performance when one of the cars was down to 9 cylinders; I lived 'in the country' so there were very few chances to stretch the legs of the car so didn't really notice.
Check all the gubbins in the boot (trunk), especially the swirl pot (accidentally designed to collect all the crap in the fuel system.