pmansson said:
2 of my CSi cars have this habbit when warm. Slowing down for a redlight or crossing, gear in neutral, and then the engine stops and the braking power is seriously reduced. Sometimes I put it in second and restart it if I have enough speed. What might the culprit be here?
There is a lengthy thread posted on the forum several weeks ago regarding intermittent stalling that may inspire a few ideas. The fact that your problems (2 cars) seem to arise when braking should prompt a second look at the brake vacuum boosters and the vacuum hose and one-way valve that feed each, as suggested by 30csl.
Somewhat inadvertently, I discovered that on my d-jet the voltage required to energize the injection system is critical if the the battery and/or alternator can't supply a solid 12 volts with sufficient amperage. I was chasing a changing idle after hard running and it wasn't until I swapped a questionable battery for a good one did I notice the difference.
Since you are experiencing this issue with 2 d-jet equipped cars, is it possible the idle speeds are too low to overcome a large and repeated vacuum draw - as might occur when you repeatedly depress the brake pedal? In addition to the vacuum demand made by each brake booster, each D-jet also has a potentiometer sitting adjacent to the booster (at least on left hand drivers) that is directly affected by manifold vacuum.
If you are familiar with carburetted cars, some would experience stalling by closing the throttle plates too quickly. Smaller engines with heavier load requirements at idle such as air conditioning and automatic transmissions with low stall speed torque converters were more prone to experiencing this. Some factories installed dashpots to prevent the throttle plates from closing completely or too quickly - as a remedy for this. Another remedy would be to increase the idle a tad. It sounds strange that you should experience this with your m30 engines, but if they are overcoming the excessive power demands of air conditioning and an whopper alternator AND you are running anything but stock cams - meaning a "lopey" idle, who knows?
Is it also possible, albeit less likely, that both cars have some loose ignition wiring (coil wire or wiring to injector points) that is/are shorted when you are braking/decelerating? Some have experienced this when making turns and a weak motor mount permits exposed/worn wiring to strike a ground or merely become detached.
Good luck.
