Hi All

 Help and advice required please.

 I have a UK Focus petrol 1.6 TI-VCT 2008 with 29k miles on the clock (Tonic Blue for the record), The problem I have is I am getting a misfire / light jerking problem only when cornering. 

 For example if I drive on a straight bit of road then take a bend I get the symptoms of a misfire. As soon as I straighten up the problem stops, This happens on either left or left hand bends and roundabouts etc, the car has never stalled or caused any real problem but now it is just getting very annoying, I never get a warning light and there are no error codes. It doesn’t matter how much petrol I have in tank.  I have changed  the spark plugs, leads and coil pack also run two tanks of redex, cleaned the throttle body. 

 I have wiggled every connecter plug without reproducing the problem. 

 Before I go any further can I have your thoughts please

 Thank you all in advance 

On 20/01/2017 at 9:49 PM, Paulb190 said:

The problem I have is I am getting a misfire / light jerking problem only when cornering. 

I find it difficult to think of a likely link between cornering and engine misfires. You have covered the low fuel one.

A rather unlikely one is the steering pump. If this car has the belt driven pump, maybe it is putting an unexpected load on the engine? Or if it is EHPAS, it can draw quite a lot of current, so a dodgy alternator, battery or earth connection might cause electrical problems when steering?

Could it be a mechanical judder, and not the engine at all?

Stiff differential, seized driveshaft splines, worn CV joint? Spinning a wheel with both front wheels off the ground should test some of this, usually turning one wheel will turn the other one in reverse via the diff.

ABS / Traction control coming in unexpectedly. Mismatched type sizes or even tyre pressures can cause this on rare occasions, but would normally be only on one hand of bend.

Many diagnostic tools are weak when dealing with ABS or steering problems. A Ford specific system like Forscan might possibly reveal something. It can directly read ABS wheel sensor speeds, for instance.

All that is not much help, I know, but maybe the above will trigger some-ones memory or thought process!

 

Quote

 

Hi Peter

 Thank you for your replay and thoughts.

 The problem is like someone is flicking a switch when in a corner and the car misfires, along with the misfire I sometimes a get a millisecond burst of power with the throttle in the same position, but again only when in a corner. I did take it to a so-called expert who apparently has the latest and up to date equipment but he couldn’t find the problem.

Maybe I try someone who has the Forscan system.

Thanks again for your input.

I have changed the power steering pressure switch but it’s made no difference,

I have noticed that when turning on a roundabout for example at around 20 mph, if I take the car out of gear and coast around the roundabout when I turn the wheel the revs increase from around 1000 to 1700, the tighter i turn the wheel the higher the revs go up, if I drive around the same bend in gear I get the jerking/misfire, for some reason the car is increasing the revs when cornering either left or right hand bends. How bazaar,

I thought it might be the steering position sensor but I have looked on the rack and I don’t have a sensor.   

I didn’t want to take it to a Ford dealer but I don’t think I have much choice.   

9 minutes ago, Paulb190 said:

when I turn the wheel the revs increase from around 1000 to 1700, the tighter i turn the wheel the higher the revs go up, if I drive around the same bend in gear I get the jerking/misfire,

I think the purpose of the pressure switch is so that if you change gear while cornering, the load from the steering pump will not stall the engine. Also when trickling along at idle speed in traffic, also more rpm is needed to avoid stalling. This is a serious concern for the manufacturer, as a stall like that can be dangerous, with sudden very stiff steering.

But why that nominal increase in idle speed has any effect when driving normally, is a mystery. It suggests there is some underlying fault in the engine that only shows up under these conditions. Also the proportional nature of it is odd, a pressure switch should be on or off.

Maybe pulsating pressure from the pump could do it, like a partial failure in the steering pump. Then constant switching of the pressure switch could well confuse the ECU, and it would get worse as steering effort increased.

I suspect Forscan will have a PID that enables you to monitor the status of the steering switch. If you can, go to the Table/Dashboard/Graph mode, and press the setup button that should appear. This will list all available PIDs for your car. It is not as complex as it sounds!

I can guide you through a way to log the switch status while driving, if you can locate a relevant PID. (You need to be connected to the car to view the list of PIDs.)

(A PID is just a number stored in the cars electronics that can be read externally, and can contain useful, continuously updated information)