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

13 hours ago, joshuafalls said:

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.

Have you checked the PCV hose? Could be split?

Have you tried cleaning the throttle body and MAP sensor? For a few quid you can buy the cleaner, and take out the throttle body and map sensor and give a spray of the cleaner. Clean the throttle body with a microfiber cloth, and do not attempt to clean the MAP sensor with any kind of cloth, just spray it.

Throttle body and MAP sensor are very easy to take out, just take off the main air intake hose and its easy access after that.

If the throttle body/MAP sensor is clogged with years of grime (like mine was) then the engine gets starved of air causing all sorts of idling issues.

Your symptoms of it being fine at 70mph sounds like what I had, at 70mph the valve in the throttle body is at its most open so more air is getting in, but at low speeds there's less air and the ECU gets confused. Might be worth a try doing this because even if it doesn't solve your problem it'll make things smoother once you've found your solution.

If you do it, make sure to disconnect the battery before starting, then leave the car to idle for 10 minutes once you've finished, and then go for a nice motorway drive to help the ECU learn to function again. You'll have reset the long term trip memory of the computer so it'll teach itself how to time the engine/fuel based on the cleaner air getting to the engine.

Link below to my previous post about this task:

https://www.fordownersclub.com/forums/topic/165057-fuel-economy-throttle-body-and-map-cleaned-what-now/#comment-1140702

58 minutes ago, Eli_P said:

Have you checked the PCV hose? Could be split?

Have you tried cleaning the throttle body and MAP sensor? For a few quid you can buy the cleaner, and take out the throttle body and map sensor and give a spray of the cleaner. Clean the throttle body with a microfiber cloth, and do not attempt to clean the MAP sensor with any kind of cloth, just spray it.

Throttle body and MAP sensor are very easy to take out, just take off the main air intake hose and its easy access after that.

If the throttle body/MAP sensor is clogged with years of grime (like mine was) then the engine gets starved of air causing all sorts of idling issues.

Your symptoms of it being fine at 70mph sounds like what I had, at 70mph the valve in the throttle body is at its most open so more air is getting in, but at low speeds there's less air and the ECU gets confused. Might be worth a try doing this because even if it doesn't solve your problem it'll make things smoother once you've found your solution.

If you do it, make sure to disconnect the battery before starting, then leave the car to idle for 10 minutes once you've finished, and then go for a nice motorway drive to help the ECU learn to function again. You'll have reset the long term trip memory of the computer so it'll teach itself how to time the engine/fuel based on the cleaner air getting to the engine.

Link below to my previous post about this task:

https://www.fordownersclub.com/forums/topic/165057-fuel-economy-throttle-body-and-map-cleaned-what-now/#comment-1140702

Hi Eli,

Thank you very much for the reply, it is driving me crazy at the moment. It seems to be the brake pedal goes rock solid as well whilst driving which is a strange symptom. I'll have a look at the throttle body but don't think my car has a MAP sensor as it has the MAF sensor on the intake pipe. I could be wrong though being the 1.6i Ti-VCT

Very unsure at the moment, it seems to be a low rpm and sounds like it's misfiring/running rough but all cylinders are firing and spark plugs okay.

Thanks, Josh

just a thought but when you replaced everything, did you reset the code?

The brake servo works on vacuum. Check the vacuum pipes for any splits or loose connectors.

1 hour ago, joshuafalls said:

Hi Eli,

Thank you very much for the reply, it is driving me crazy at the moment. It seems to be the brake pedal goes rock solid as well whilst driving which is a strange symptom. I'll have a look at the throttle body but don't think my car has a MAP sensor as it has the MAF sensor on the intake pipe. I could be wrong though being the 1.6i Ti-VCT

Very unsure at the moment, it seems to be a low rpm and sounds like it's misfiring/running rough but all cylinders are firing and spark plugs okay.

Thanks, Josh

Yeah I don't know the ins and outs of which models have MAP/MAF but throttle body definitely worth a go. Will help your engine get better air even if it doesn't solve everything

2 hours ago, joshuafalls said:

It seems to be the brake pedal goes rock solid as well whilst driving which is a strange symptom

As Tom says that strongly suggests a loss of vacuum to the master cylinder. A vacuum leak would introduce air into the intake downstream of the MAF sensor which would cause an incorrect reading and most likely account for the poor idle. This would be less apparent at large throttle openings hence why the car is ok at 70mph. I'd definitely look for a leak.

22 hours ago, TomsFocus said:

The brake servo works on vacuum. Check the vacuum pipes for any splits or loose connectors.

Thank you very much for the 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