Car auto revving

Tatooine Hobbies & Interests
1

Drove home from work today and whilst sat in traffic, noticed that my car was revving itself, even with my foot on the brake and clutch.

Was going up from about 1.5 on the rev counter to about 2.5 then dropping off and then repeating. All the time. Was slightly disconcerting.

Is it something I should be worried about? It didn’t do it yesterday on the drive to East Midlands parkway to pick my brother up and it didn’t do it this morning when I wasn’t stuck in traffic.
I’m low on fuel but I don’t see how that can cause it.

2

fuel starvation may make the pump kick in and work harder, and when it hits the engine it revs up ??

Fuel filter possibly, if you’re that low it’s pulled the muck out the bottom of the tank through.

DT.

3

OK, that might be true as I’ve not let it get this low for a while.

4

either that or automatic choke kicking in falsely? Occam’s razor states that DT’s answer the right one though :smiley:

5

Has the engine fault light come on and gone off again in the last few weeks ?

There are a few things I know of which can cause this, mass air flow sensor faults, Exhaust gas recirculation (EGR) valve and a temperature sensor fault have all caused this on various cars I’ve had in the past.

What car is it and what year ?

I have an OBD-II code reader you can borrow (if its newer than a 2002) which should read out any stored fault codes from the engine.

6

DTs probably right. It could also be a faulty engine temp sensor giving the ECU a bit of a hard time trying to work out what mixture to squirt in. TFWs diagnostic tool should assist you

7

It’s an 02 reg Ford Fiesta. And no, not seen the engine fault light on at all.

And anything under the bonnet to me is greek…

8

Not much clue on how Fords are set up but generally an inlet manifold air leak can sometimes give this symptom.

Have a look to see if any of the ancillary hoses connected to the air inlet between throttle body and engine are loose or split (eg brake vacuum line, fuel pressure regulator, idle air control etc)

9

Take it to fords, it’s a known issue, I had it on my Ka.

10

Erm, taking it to Ford would be at the bottom of my list of options.

Ford quoted £2600+vat to replace my gearbox.
An independant garage fitted a reconditioned unit and a clutch for a bit over £1000

Ford had three attempts at fixing my Air-conditioning at two separate dealerships
An independant fixed it for £100, mentioned the word “Muppets” and its worked perfectly for three years or so.

Try a couple of independant local garages, the sort you find in your free papers or parish council news letter.
You might find a good mobile mechanic that can fix it but I found they only want to do the electronics side when I was phoning round a few weeks ago.

Those big shiny showrooms full of new cars cost money to keep shiney and clean and you only need the workshop bit to get your car fixed. No real benefit going to a dealer once its out of warranty.

11

It seems fine again now since filling up. However, I didn’t then drive in in atraffic jam AFTER filling up so that’ll be the test.