Focus 1.8 Zetec revving/idling problem

Fuel cut off fault perhaps. FI cars should cut the fuel when you lift off above certain rpm and/or road speed to save emissions and petrol. Sounds like yours is still pumping fuel in unless the car is stationary. Maybe it's the road speed sensor at fault but this is not really my area of expertise.

If the intake system is really that badly clagged up then maybe it's breathing a bit heavy anyway. Do a compression test.

Thats got me thinking - also if the throttle position sensor wasn't showing zero throttle at lift off, would the ECU still try to inject fuel, and if so, would the engine continue to rev despite the closed butterfly valve?

Just trying to get a handle on how these systems inter-react.

Cheers,

Gareth.

Yes, and yes, but a stuck TPS will cause a stuck high idle on these. The programming is also such that immediately you lift off it fully opens the ISCV which lessens engine braking. It's an emissions thing.

What rpm does it idle at stationary in neutral, clutch up, a/c off? Should drop to ~650rpm after about 1 second of holding at 900rpm.

Does it warm full up hot- i.e. thermostat? If not then this will make the idle speed hang, as will a faulty PCV valve (common- under the ex manifold)

Having said all of that, all Foci tend to display what you may initially find un-usual idling characteristics- it is how they are programmed. Idle flare on cold start to 2000rpm is normal too, and so is other behaviour the moment you hit the a/c.

Tim.

On Ford Focus, this is caused by the Throttle Position Sensor being faulty.

Replace it.

You can clean up the ISCV, which is a good idea as a service job anyway, but you will still likely have to change the TPS to cure the fault. Once swapped out, reset your ECU by disconnecting battery or take out appropriate fuse for a few hours.

I have the same problem, but a new ISCV was fitted 1000 mines ago and i chanced the TPS for one from a donor engine and still same problem. It maybe a coincidence that they are both TPS are nakkered, but could it be anything else?

Regards

First check is that there are no intake air leaks especially the breather pipe on the back of the manifold, assuming there are none then the symptoms are very typical of a faulty ISCV. I have tested quite a few tps sensors and have not yet found a faulty one.

The reason that the iscv is pointed to is because it actually opens when you are driving along and then shuts itself when the throttle is released. To quickly ascertain that it is the iscv: disconnect it. Drive it, you will need to keep it idling by using throttle, so pick quiet roads/day. If you find that it now behaves correctly during gear changes then it is the iscv.

Interesting; both my 1.6 and 1.8 Focuses idle at exactly the same speed whether the ISCV was connected or not. The only difference it made was that if you puts lots of idle load on, it slowed a bit. Not enough to stop it idling however.

Chris

I have found both situations, I drove mine for several months disconnected and had a reasonable idle, it even went through the MoT, but I have also found ones that have no idle at all, it may depend on how the throttle plate is set in manufacture. Either way, if the revving during gear change fault goes with it disconnected then it will be the iscv.

As an ex Ford master tech I used to see these sorts of problems with mk1&2 Foci daily.

Firstly,do you have working and adjusted clutch & brake switches; these can be kicked out of position and will cause the above symptom. Check these FIRST.

If the idle rpm's drop by more than ~100rpm or so at a hot idle, electrical loads and a/c OFF then the throttle body needs cleaning Yes I know the sticker says dont clean it, but it must be shiny clean. (On a 1.6 check carefully the PCV system as they are prone to blockages and leaks and on the 1.8/2.0 just leaks; if the oil filler cap is being sucked on then fix the PCV system first. There should be just a small amount of vacuum present at the cap with it working properly.

The PCM doesnt just use the ISCV to control idle, it also adds ignition advance to help. As someone else said, yes the ISCV is opened during cruise and decel even when the throttle is CLOSED and fuel cut off- reduces pumping losses.

The TPS must show 0.8v or less with closed throttle, otherwise you will have issues with idle 'hang and flare' (Ford term) The slots in the TPS can be filed out to get a low enough voltage if you are having issues, even with a new genuine ford tps. On the 1.6 there is a modded tps wiring loom and connector available, but I would expect 99% of cars to be now fitted with it, as well as the modded CHT sensor wiring.

With the a/c turned on, the PCM uses a different idle / low speed strategy ; there will be a certain amount of flare and hang at times, this is Normal, as is some 'mush' (yes another official Ford term) at the lower end of the rev range.

Regards, Tim.

What is this word 'nakkered'? Do you possibly mean 'knackered"?

I checked for leaks and couldn't find anything,i also swapped the ISCV with two others i have and i still have the same problem, But when i disconnect the ISCV it doesn't happen. I'm due to sell the car in a weeks time.

any other ideas?

have you tried a new iscv, they are quite cheap off ebay and work fine

Did you also check the clutch and brake pedal switches are in place and switching properly?

Chris

Yes it has a new one on. The switches look to be working fine too.

"look" is entirely different from "electrically switching" .

Tim.

They have not been kicked or knocked out of like as said previously.

So you haven't established that they're working yet?

Tim

Hi there I recently ctanged the alternator on my Ford Focus saloon. After I got the engine back together I tried stating it. The idle speed had dropp ed to around 200rpm and then cut out. I tried moving the car and it runs f ine.

On closer inspection of the engine I noticed a pipe was broken which runs f rom the fuel intake over the alternator then along the bulkhead to the thro ttle body. I have replaced this which has improved it some but not cured it . I have noticed what seems to be another 2 pipe connections at the back of the throttle body. I don't know what these are or where the pipe if there is one should go.

When the engine is at idle it will do 1 of 3 things it will rev to low as m entioned before or it will go to the other extreme and Revs at 3to4000rpm. Sometimes it will idle at it's normal 1000rpm but it won't be steady the en gine will hunt.

What could cause this and how do I fix it?

commonly it is the breather pipe which is low down on the back of the inlet manifold, it leads around to underneath the coil pack, it eventually connects to the engine breather box below the exhaust manifold. very cheap and often fails.