fiesta 1.25 zetec labours above 4000 rpm. Solutions? (2023 Update)

Well it won't be an auto choke. Chokes are for cars with carburettors. Yours has injection. That clears that one up.

That's the problem with a lot of garages these days. So many of them are a bunch of clueless fuckwits who'll tell you what the computer says but can't actually find what's causing that problem. Engines aren't *that* complicated these days. It's still the basic suck/squeeze/bang/blow principles, just a little more complex on how much is sucked (and the rate it gets sucked at), exactly how much it's squeezed, exactly when it goes bang, and how easily it goes blow.

Take it to a garage with a clue.

Peter

For a start the last part is bollox. The ECU (at least on this Fiesta) is not able to directly measure fuel pressure- it has no sensor in the fuel rail. (it could signal a long term fuel trim value exceeded though- but this could be caused by more things than just lack of available fuel)

You have one of three problems:

1) ECU entering limp home mode due to major sensor speed related failure- eg cam sensor or MAF. This would be my guess. Fiesta's of this age do not have a MIL lamp to indicate a fault.

2) Restricted fuel supply- blocked line / filter or weak pump- would only show under high load / wide throttle openings.- is it better in a lower gear with a smaller throttle opening revving past 4000, or the same?

3) Restricted Exhaust (but this would be apparent both hot and cold and not suddenly at specific revs)

Does the car misfire at all, or is it just holding back ? If its missing, or spluttering then you have an ignition problem.

Has fuel consumption increased suddenly?

Tim..

Good point about the choke!

This garage suggested the many things it could be. But they said without changing them all one by one they couldn't be sure. I was trying to avoid the cost of changing all the working bits as sods law says they have to change them all before they find which one it is!

Chris

They just said they plugged their box into the car and it indicated low fuel pressure. Or I misunderstood. Would a genuine ford garage be able to diagnose more?

(or knowing my luck 3 of three ! ;0)

This was suggested

In each gear 1-3 it revs to approx 4100 and then acceleration is markedly less. It may do this in 4th as well but that would be over

70mph I think so I can't be sure ;0) as I haven't tested it, honestly. It seems to be almost exactly the same in each gear (within 100 rpm). The filter has already been replaced to try to alleviate this. Could the fuel line get trapped/pinched by jacking or other work carried out during a service? I'm assuming its metal and so would remain the shape it was squashed to. Remember, although it misfired when cold before the service it did rev freely above 4000 rpm and its only since the service its had problems with high revs.

Agreed, I'm assuming it would sound different too and afaict its still the same.

It only misfires when "cold and being gutless" pulling away but after

2-3 minutes it runs smoothly. It runs smoothly above 4000 rpm too sounds just the same, the only difference is the acceleration. Having said that it started OK from "cold" today (but it is hot outside!)

That's a difficult one as I didn't drive the car much before but I've just been told it used to do about 220 per tank (to red) and now does about 180. Since I've been using it more its done 200 ish but as I use it infrequently (relatively) I don't tend to fill it up. We tend to reset the trip when we fill up so these are quite accurate.

Anybody care to suggest a most likely cause or a the cheapest sequence/method of getting this sorted?

Thanks for your replies BTW.

Chris

They just said they plugged their box into the car and it indicated low fuel pressure. Or I misunderstood. Would a genuine ford garage be able to diagnose more?

(or knowing my luck 3 of three ! ;0)

This was suggested

In each gear 1-3 it revs to approx 4100 and then acceleration is markedly less. It may do this in 4th as well but that would be over

70mph I think so I can't be sure ;0) as I haven't tested it, honestly. It seems to be almost exactly the same in each gear (within 100 rpm). The filter has already been replaced to try to alleviate this. Could the fuel line get trapped/pinched by jacking or other work carried out during a service? I'm assuming its metal and so would remain the shape it was squashed to. Remember, although it misfired when cold before the service it did rev freely above 4000 rpm and its only since the service its had problems with high revs.

Agreed, I'm assuming it would sound different too and afaict its still the same.

It only misfires when "cold and being gutless" pulling away but after

2-3 minutes it runs smoothly. It runs smoothly above 4000 rpm too sounds just the same, the only difference is the acceleration. Having said that it started OK from "cold" today (but it is hot outside!)

That's a difficult one as I didn't drive the car much before but I've just been told it used to do about 220 per tank (to red) and now does about 180. Since I've been using it more its done 200 ish but as I use it infrequently (relatively) I don't tend to fill it up. We tend to reset the trip when we fill up so these are quite accurate.

Anybody care to suggest a most likely cause or a the cheapest sequence/method of getting this sorted?

Thanks for your replies BTW.

Chris

Got it. Obvious really.

They've put a diesel in.

Ok, you say that this problem started only after the car was serviced. Its possible that the garage have changed the spark plugs, possibly set the gap too large (Ford reduced the recommended gap on these engines) and this has put a strain on your HT leads. If you have got your original HT leads fitted then they will definitely be knackered at 80k miles.

The Zetec SE engine is very reliable and any problems that do develop are overwhelmingly down to plugs, HT leads and the coil pack.

Its important that you use genuine Motorcraft leads and either Motorcraft or NGK plugs. Anything else and you will have more problems sooner rather than later.

I'm inclined to agree with this at least partially, you cant diagnose faults like this for sure at a distance, but as Paul says, the HT leads will be completely shot if they have more than ~60k on them. The surface of the coil pack needs to be eat-your-dinner-off-it clean and the plugs fresh and correctly gapped, and the plug wells clean and free from oil too.

It could be a case of the coil pack tracking over its surface to the LT multiplug or an HT lead flashing to an ECU line which is spiking the ECU and causing it to shut down / enter LOS mode.

Tim..

Get a odb2 bluetooth adapter, connect yo your phone and use torque to read the throttle position. if pulling at full throttle, torque reads anything BUT 100%, then it's your throttle positioning sensor. Clean it our or replace it.

Or a obd2 to usb adapter and use Forscan

Both Forscan (for Ford based cars) and the Torque apps are good.

Great advice, 17 years late.

Tim