Strange electrical problem Ford Focus Mk1

[Benkitonk]

High there, I'm in need of some help. My mk1 Focus is behaving strangely and I wondered if anyone had an ideas as to the cause. I think it's electrical. It started two weeks ago, a few days after I fitted a new usb cable to the head unit to connect my new iPhone. Previously the usb had run to a glove box mounted hard drive. I changed this to a usb to lightning cable to plug my iPhone in, when I'm using the car. This might be a coincidence, but I'm adding for context. A few days later, whilst driving the car, with about 100 miles done that day, both wipers wouldn't work on intermittent only. Then the engine started behaving a strangely. It would kangaroo a bit but in gear and at speed. 30-50mph. It got me home and over the next two weeks it has got slightly worse. The engine warning light came on for two days and has now gone off. The boot open light will come on and go off when driving too. Also the speedometer will under moderate acceleration, jump up 20-30mph above the actual speed before settling to actual speed. I have check, cleaned and removed the plugs and leads. They look fine. As does the coil. I have checked and cleaned the battery terminals. Halfords checked the battery and said it's producing 417 amps from a marked 425. I have checked/removed and replaced all the fuses. I have also checked and cleaned the main battery earth. The car has 116000 on it and is only worth about £400, but I'd like to keep it running for another year of so. Has anyone experienced anything similar? Cheers

[Tdci-Peter]

5 hours ago, Benkitonk said:

both wipers wouldn't work on intermittent only. Then the engine started behaving a strangely. It would kangaroo a bit but in gear and at speed. 30-50mph. It got me home and over the next two weeks it has got slightly worse. The engine warning light came on for two days and has now gone off. The boot open light will come on and go off when driving too. Also the speedometer will under moderate acceleration, jump up 20-30mph above the actual speed

Hi Ben,

I can only think that some major connector has developed a bad connection somewhere. Maybe partly due to disturbance, maybe it was going to happen anyway. Double check all the connectors around the glovebox area, there may also be some behind the trim panels in front of the passenger door. And in the engine bay fuse box. Look for water ingress or corrosion etc.

The symptoms are also consistent with low battery voltage, you have looked at the earth, but more checks & measurements there might help.

I do not have much info on the mk1 Focus, so am having to guess a bit here, but speedo usually involves the pcm (engine computer) & Instrument Cluster, rough running is usually a sensor or output device connected to the pcm, wipers and boot light are the GEM (aka BCM or body control module). So it is very hard to see any link, apart from system voltage or some major connector.

And I strongly recommend getting a diagnostic scanner for when the engine light comes on again. It might yield a vital clue. I think an OBD2 scanner should work, though OBD compliance was not required until 2002 for petrol cars, I seem to recall. Forscan (with an ELM327 adapter) can diagnose a Mk1 Focus. Forscan can also read codes in the GEM, which a generic scanner will not do.