325i cutting out at speed?

[MajorBob]

Hi all, I’ve searched through the threads and found similar but not the same issues. Here is mine: While driving normally, either cruising on the highway or around town. my 89 325i vert will suddenly lose all electrical and engine power and coast for a few seconds after which it "switches" back on and everything is fine again. It has done this about half a dozen times in the last two months. I have replaced the following, Crank sensor, CO2 sensor, throttle position switch, rotor and cap but the issue still baffles me. Any ideas what to check next? Thanks!

[dnguyen1963]

Check all your grounds.

[MajorBob]

Thanks, I thought of that also and checked but all apear to be secure.

[barry]

Main Relay or wires to it, Faulty fuel pump or relay. Clean all your wires and plugs with CRC

GL
Barry

[jlevie]

Does the car lose all power? That would mean headlights, radio, HVAC blower, etc. Or does only the engine lose power? The former could indicate a problem with primary power distribution and latter with an engine management problem. What does the tach and econometer do during an event?

[MajorBob]

Yes, everything cuts off, including tach. The spedo stays on though? Not sure about the lights, since this has only occured during the day but I would suspect the light go out to. Also, and I should have mentioned in the original post, I have replaced the Fuel pump and relay. Thanks Guys!

[jlevie]

If the speedometer continues to work, the car isn't loosing power. The tach going to zero indicates that the engine speed signal from the DME has gone away. That can be caused by a loss of timing data to the DME, a loss of power to the DME, or a fault in the DME. The first suspects in a case like this are the main relay, fusible link, and CPS. A bad DME or a bad engine harness possibilities, but start with the easy stuff.

[MajorBob]

Thanks Jim, Ill try to run those down this weekend.