Ian T

Hello all, this is my first post and I'm, like many other people I guess, registering because I'm hoping someone can help me track down a silly fault that's got me foxed.

I've been into (ahem) Vauxhalls for the last 20 years or so, but bought this Focus to run through the winter, not least for the heated seats and front windscreen. It's only had a couple of owners and was last sold through the Ford Direct scheme by the looks of it.

It's a 2.0 Ghia on a 52 plate, with manual box.

The hesitation only seems to come on as the engine warms up, it starts easily, idles well and accelerates well when the throttle is opened well, but at part load, such as cruise or light throttle as you would when travelling at constant speed up a very slight incline at lowish revs (1500ish), the engine feels like it is hesitating or hunting. Sometimes it feels rythmic, but not always. When running lumpy, accelerating hard suddenly clears it up and it accelerates smoothly and the power seems to all be there.

When the engine is hot, there is no such fault and it generally seems to be fine.

So far I have done some logging on IDS, found nothing much of consequence, so gone with some hunches as follows:

1) Checked for vacuum leaks, found and fixed a small hole in the nylon pipe across the back of the bay to the black (reservoir?) on the bulkhead that (I haven't checked) may connect inline to the brake servo (no difference)
2) Checked rubber hose elbows and joiners for damage and collapse (nothing evident)
3) Checked the fuel pressure regulator - inconclusive, as unplugging the vacuum line and plumbing it to a syringe seems to have no / little effect on idle speed running as vacuum is introduced.
4) Fitted new spark plugs and genuine Motorcraft leads (no effect)
5) checked the MAF (cleaned with electrical contact cleaner, was already clean)
6) Replaced coil pack (seemed to help the first time I drove it afterwards, but overall hasn't made a difference).

For those familiar with this engine, at idle revs with the engine hot, the data from IDS is pretty stable:
VPWR: 14.18V
TP: 0.93V
SHRTFT: -0.98% (steps up and down slightly every second or so)
LONGFT: -7.81%
RPM: 717rpm (nominally 700)
O2S11: Oscillates between 0.04V and 0.8V slowly (every 5 seconds or so, every second at when the car is moving)
MAF: 2.37g/s
MAF: 0.65V
LOAD: 18.04%
IAC: 375mA
IAT: 11.00 deg C
CHT: 94.00 deg C
EVPVM: 29.25%

The only thing I can see in that data is that the long term fuel trim is nearly 8% negative, which makes me wonder if I am still missing a vacuum leak or something similar.

Any suggestions would be really welcome.

Thanks,

Ian.

studabear

Has the fuel filter been replaced recently?

Ian T

Probably safe to assume not, although given it goes like a train on full throttle I had kinda ruled that out. A bit of previous googling suggested that the filter was supposed to last the life of the car and was in the fuel tank, but with such a long lived model, it's hard to know for sure.

studabear

A 52 plate focus has a external filter, its on the offside between tank and floorpan, you need a 8 or 10mm socket and extension to lower it down, then a 7mm (iirc) to release the filter from the cradle.

Ian T

Thanks,

I'll replace it and see. Wouldn't you expect it to lack power higher up in the rev range if it was blocked though?

Cheers,

Ian.

studabear

Hard to say, but sometimes your better starting with the basics.