Rev Counter Going High Then Low

[stacy30]

I have a 56 reg focus ghia.

When i first start it up its fine but after a few minutes when i push the clutch down to stop the rev counter will go really low and the battery light will flash on then the revs will shoot back up just before the car stalls. it will yo yo up and down like this until the car has warmed up then it is fine. Today for the first time the revs dropped that much that the car stalled. The car has only been doing this for a few weeks and it is slowly getting worse. There are no fault lights on, and the car always starts fine.

Does anyone know what this could be?

[Lenny]

I have a 56 reg focus ghia.

When i first start it up its fine but after a few minutes when i push the clutch down to stop the rev counter will go really low and the battery light will flash on then the revs will shoot back up just before the car stalls. it will yo yo up and down like this until the car has warmed up then it is fine. Today for the first time the revs dropped that much that the car stalled. The car has only been doing this for a few weeks and it is slowly getting worse. There are no fault lights on, and the car always starts fine.

Does anyone know what this could be?

Hi,

Welcome to the forum,

sound like the battery is low or on its last legs,

could also be the altinator (thats the thing that charges the battery when the engine is running)

but if the altinator fails or is intermitant that will also drain the battery,

you see once the engine is running, the altinator should charge the battery and power all electrics on the car too.

hope this helps and Merry Christmas

[Danny87]

As Lenny said the battery or alternator is a possiblity, especially with the much colder weather we've been experiencing lately. It may be worth telling you I had a similar issue and it was the battery, I isolated the battery as the problem by measuring the voltage drop over one night using a multimeter and keeping records of the voltages and amps as they fell.

Do you find your trip counter resets when you start the engine? Mine did this too, presumably because the ECU was being starved of voltage just as the engine would crank and the starter motor needed all the power. The engine revs would dip and yo-yo as you describe because the ECU learns settings based on the climate etc, if the voltage has been cut then it will lose these and the engine runs like a pig until it learns again.

Hope that helps, I've pretty much repeated Lenny's advice - it's likely to be either your battery or alternator! :D

Merry Christmas!

:)

[stacy30]

Hi,

Thanks for your replys.

I had the battery and the alternator checked and they were both fine. They also ran a diagnostic on it but no faults came up. I had the throttle valve (i think this is the name of it) cleaned out and still no joy.

I did read an article about learning the ECU to learn about the cars idle speed again. It said to disconect the battery for 15 minutes, start it up and run it for 5 minutes without touching the accelerator and then taking it on a long drive. Does this sound like it could work?

Do you have anymore ideas what it could be please?

Thanks

[Danny87]

At this stage I think it's certainly worth a try. Disconnect the negative terminal and leave it off for about 15 minutes, connect it back up and start the car again. You may find this will solve the problem you're having, also assuming you have the original Ford stereo fitted make sure you have the code as you'll need to put this in afterwards before using it again.

It's not absolutely vital how far the car is driven afterwards, I'd say no more than about 5 miles or so just letting the engine get up to temperature.

Dan

[greggp]

Check your throttle body! Not a cheap repair so for your sake i hope it isnt but sounds similar to my problem.....