Hi,

You are all probably aware about my recent troubles with my focus and it hesitating and surging mainly around corners then remains rough afterwards.

I have done some more test with the obd2 bluetooth kit and using an app on my android.

I tested the map sensor readings and im thinking there not quite right.

When going in a straight line on a road the map readings are normal and change slowly up and down depending on throttle. When going round a long bend or roundabout with my foot still on the accelerator the car was ok until it started surging and the map readings went and and down quite considerably. I was doing around 3k revs in 2nd gear around the large roundabout and the map was fluctuating quite badly.

Could this be faulty or is it fuel related.

I hope this might answer some questions, i also recorded the live data and have a video i could upload if anyone can help.

MAP will change because of the stutter unfortunately

Still think you have a wiring short somewhere (Fuel pressure sensor?) and the G force is moving the wire and shorting something out

It does it more in 2nd gear with higher revs

The map sensor will fluctuate as the fueling is up and down http://en.m.wikipedia.org/wiki/Mass_flow_sensor

In short it doesnt mean thats the issue

But when in a straight line it doesn't fluctuate round a roundabout only when it hesitates it jitters

Precisely if it was the issue it would fluctuate in a straight line its only doing it when you get hesitation meaning its just responding to the fuelling issue

didn't you say it does it going up hills at low rpm as well? both up hill and around sharp corners both exhibit a couple of different forces on liquids that could effect things if its not right. same could be said for shorting out wires but I think that would be less likely. whilst air does act like a liquid it wont have such a big effect in a car engine.

what does the fuel sensors say when doing all this?

Both times also are situations when the engine moves on its mounts, hence why I think its a wiring short

I have a long term fuel readout. When the the car was stationary it was at .79 when I accelerated normal it went to minus .77 and stayed there. When I went round the sharp corner it went to between 0 and plus 2.34 now afterward it stops in 2.34.

yeah its possible, the corner is a lateral force and could easily move something like a wire but the hill (if it was doing it on a hill?!) would just be torque movement and the angles of the incline would be completely different to a lateral force put on them plus you could recreate that anywhere.

Going the wrong way around a roundabout would probably push wires in a different direction which might help eliminate things too.

But the fuel is as good a bet as any as it would be affected by all of those things, left right lateral force and inclines.

But Im not an expert at all though, most folk on here will know more then me, im just thinking physics which can fairly easily be checked and eliminated.

I have a long term fuel readout. When the the car was stationary it was at .79 when I accelerated normal it went to minus .77 and stayed there. When I went round the sharp corner it went to between 0 and plus 2.34 now afterward it stops in 2.34.

not sure what those numbes are all about, but it looks like it got lower when you accelerated then got higher around the corner and stayed that way....

I think you'll need more detailed recordings to see what its doing allowing you to compare RPM, Speed, throttle position, fuel PSI, flow rates etc, get the engine up to temp before hand for a few min, try some long bends, tight bends, left and right, hills etc, get someone to record the times of each one so when you look at the trace you can say, ok, on hill x this was happening , corner y, this happened but corner z it didn't. That kinda thing, it might not pin point anything but it might help eliminate some stuff

Those are weird fuel readings. Wonder what units they are. Looks like movement is altering the fuel pressure, so could be electrics to the pump, physical movement of the pump, Maybe the pump is knackered and cant handle the G force or fuel load, or maybe even a small air leak in the piping which opens up under load

Id check the fuel pipe, front to rear for any damp spots, and then put a multi-meter on the fuel pump and corner her to see if the voltage varies, that will help narrow it down

S

Yeah a local indy garage said the symptoms when he drove the car was a possible fuel pump issue. But the main dealer said all was ok.