Car mechanic/auto eletricians/tinkerers.

Car: 2004 Focus 1.6 LX Indestructible.

Issue:

Speedo randomly drops to zero for a few seconds every 100 miles or so, for a period of about 5 seconds. Stereo also quietens (AVC?)

After a few weeks, the frequency remains the same, but lasts about 10-20 seconds.

More recently, happens every journey and today triggered the engine management light.

When it happens, the throttle response is…..different. Not sure what, it’s either less ‘analogue’, or there’s a delay – not figured out which yet.

No discernible triggers, but always happens on motorway journeys. However, the poor thing is only doing motorways journeys in the main.

A trip to the Co-op this evening, and the engine management light was no longer present.

The value of the car doesn’t warrant being booked into the garage to be resolved(although a service is due, so I will bring it up then) but do the symptoms point to anything obvious that I can tape/hit/massage?

If it involves removing all the interior, or buying ropey replacement injectors from the internet, I’ll just live with it.

Ta.

If you had said Ka I would have said Abs unit, but the only thing i have changed on a focus was a dicky speedo sensor which is located on the gearbox.

From the first symptoms you mentioned I would look at the earths. Start at the battery and any others you see in the engine bay. Remove the leads, clean up and refit. Also check the earth from the fuse boxes.

This will probably be the speed sensor mounted on the gearbox. (SNAP!)
Mine (1.8LX) had that occasionally fail & the symptoms were power-steering assistance changed (went heavier) and engine response flattened (not as bad as limp mode, but same idea).
I had an aftermarket stereo without speed input, so didn’t affect that.

It’s a common failure & an easy fix.

+1 Speed sensor, easy fix if you can get it out. As I recall the retaining pin can be a bugger if seized.

Great stuff; sounds relatively straightforward. Thanks for replies.

Indeed, the dash is loosing the vehicle speed input. When this happens, the speedo goes to zero, and the radio gets quieter because the car has “speed sensitive radio volume control” (ie it automatically turns up the radio as you drive faster). The Engine feels different to drive because the accelerator pedal mapping (and a load of other things) switch into a “idle / car not moving mode” rather than the normal “car moving” mode.

So, you need to find out where the issue lies:

As it seems to be only the speedo dropping out, the most likely fault is the speed sensor or the wiring from that sensor. As your car is quite old, i will assume it is not “CAN” based for this, and the dash display gets it’s speed information via a “hardwired” connection from the sensor itself. This hardwire will carry a “Pulsing” signal, who’se frequency varries with road speed. It might come from a basic magnetic sensor fixed into the gearbox, or it might come from the ABS unit. If you get a vehicle wiring diagram it should be easy to find the source of this signal and trace it back etc

isn’t this the known problem; £99 fix?

http://www.honestjohn.co.uk/forum/post/?t=62482

Apologies MaxT, only just seen this. Cheers for taking the time to reply.

Today the digital readout thingy completely blanked out when it happened, then returned a minute later without any miles covered, added onto reading…

I sense an opportunity to sell on with unclocked miles….For Sale: Focus, with only 180k on the clock!

haven’t read the whole thread.Maybe check the earths and cables. Clean and refit after discounting battery.