[turbojoshua]

Hi There,

I have the Focus Mk2 1.6i Ti-VCT and over the past few weeks occasionally when the car is idling it will misfire or burble as I could explain and the odd backfire heard when driving/changing gear. The past few days it has been getting worse when taking the car out of gear when driving it will just die and the idle is very eratic!

There was a fault stored for "Ignition B Circuit: P0352", I have since changed the spark plugs, ht leads and coil pack to which no difference although I did notice cracks in the airbox? I have noticed when accelerating as well from 30mph+ there is no misfire or rough running, it seems to be only from low speeds or idling, car pulls fine at 70mph.

Sorry to drag on, this is really making me pull my hair out. Hopefully someone can help?

Thanks,
Josh

[NMNeil]

Is the oil dirty? because dirty oil can cause the VCT solenoid to stick and give the symptoms you describe.
Other than that all we can do is guess.

[turbojoshua]

@NMNeil Thanks for that Neil, the oil was changed mid December for its MOT. Such a strange one haha

[NMNeil]

There's a good, if not the best way to test for vacuum leaks which may be the issue, but it's dangerous. So safety glasses, and if you have one a fire extinguisher handy.
With the engine idling direct a very very very gentle spray of carb cleaner around all the gasket areas that connect the throttle body and intake manifold with the engine, and anywhere on the engine that has a vacuum line. Spray a little, then stop, then spray a little more.
If the engine note changes, you have a vacuum leak which needs fixing.
I'm only suggesting this as you mentioned a cracked air box.

[turbojoshua]

Originally Posted by NMNeil

There's a good, if not the best way to test for vacuum leaks which may be the issue, but it's dangerous. So safety glasses, and if you have one a fire extinguisher handy.
With the engine idling direct a very very very gentle spray of carb cleaner around all the gasket areas that connect the throttle body and intake manifold with the engine, and anywhere on the engine that has a vacuum line. Spray a little, then stop, then spray a little more.
If the engine note changes, you have a vacuum leak which needs fixing.
I'm only suggesting this as you mentioned a cracked air box.

Thank you very much for the very detailed reply, I found a hole in the PCV valve pipe from the head to manifold. I've replaced that and she is running normally again although last night she somehow popped the HT leads off cylinders 1 & 2 and these were located properly. Very strange, will have to monitor how she gets on now