Do engine management systems "reboot"??

I have a 2001 Focus 1.6 Zetec, occasionally after a cold start and driving about 5km or so, the speedo drops to zero, the car runs "rough" for a couple of hundred metres - then suddenly all is back to normal.

The other day I think I "crashed" the system as I had just left work, I was going down a long hill to some lights, so let the car coast down to the red light (could be relevant, as it may have really confused the system).
Shortly after pulling away, the same thing happened but the odometer displayed ======= instead of miles travelled, it was like this for about 1km before it recovered.

Is this a "feature" or an early warning of catastrophic failure?

gofaster_s13

Engine management ECU's can be rebooted but it's not somthing which happens automaticly there is usually a process for rebooting them.

Captain Slow IRL

Instrument clusters seem to be a weak spot on your model car - not sure if the rough running is caused by it though. Does the fuel and temperature readings go to zero when this happens?
If you bring it to a ford dealership, or specialist, they might be able to reprogram the cluster - if that doesn't cure it, you're probably looking at a new cluster.

Slidey

Sounds like the whole car is losing power.

Check earth straps and connections

markos79

to reboot your ecu just disconnect the negative on your battery for about 20 mins.

bazz26

Another comon issue on that model Focus was ignition coil pack failure.

The only real way to find out is to have the car hooked up to a diagnostic's computer. Anything else is just speculation at this stage.

jetfiremuck

Could be speed sensor.If you have cruise control check if it drops out of cruise control when the speedo drops it may mean the speed signal input to the ecu may be at fault

Update!

I still have the same issue, the dropping of the speedo to zero and dimming of lights still occur at approximately 5 miles into a journey, someone suggested that it could be an actuator (end stopping or sticking) within the engine that operates when the engine is at operating temperature, that would make sense as the "reboot" happens earlier on warm days than on cold days.

Any suggestions as to what this "actuator" could be would be welcome, it's more of an irritation than a show stopper.

Update:
I have found this while googling around, it appears to be the solution to the problem I have.

Will try and do the work suggested and hope for the best.

AugustusMaximus

The speedometer issue happened to my focus. It was due to the speed sensor which needed to be replaced.

I can't remember have any engine trouble when the speedo would fall to 0 though.


Nothing to do with the ignition coil I'd say. That went in my car too. This is very noticable. You would get a burning smell in the cabin and there is a monumental lack of power.

Solitaire

Speed sensor seems to be an issue on the Mk1 Focus, lots of people claimed ECU failure and have been merrily reprogramming the thing but most of the ECU issues seem to originate from the sensor - telltale symptom being the speedo zeroing out seconds before all hell breaks loose with the ECU and engine.