Spent a lot of time reading and searching these forums, but unable to pinpoint my problem from other threads and noticed you are all very helpful so signed up!
I have a 2007 (57) 1.8 Petrol Duratec HE focus on 98k miles with a bit of an issue which I, and two garages are having trouble dealing with.
When the car is hot, i.e. mainly after travelling for around 8 miles on a dual carriageway at 70mph and around 3.4k revs in fifth, the car starts hesitating them coughing. t doesn't do it so much on A roads at lower speeds, though does have issues climbing longer hills.
So, if I'm driving along the dual carriageway and slow for a lorry, when I pull out to overtake the car surges sometimes, feels like the drive is pulsating (as if I'm slowly pressing on and off the accelerator) and often "coughs" and jolts.
This will happen then for the rest of the journey after I leave the dual carriageway, until the car is switched off and left to cool.
Associated with this, when I have the passenger window down, after around 15 minutes of driving on an A road, every time I use the throttle I hear a sound which I can only describe as someone shaking ball bearings gently in a tin can! My dad drove it and suggested it sounded like pinking, though he also feels, like myself that it's coming from underneath the car. Doesn't do it when cold.
Should also point out that just before the car hesitates, it produces a different engine note, much like I've put a "performance" air filter in. It then hunts a bit and coughs (like a misfire, but I'm told by my dad, (font of all knowledge) that it's not that.
What I've done
- Taken it to a Ford dealer - no faults, they couldn't find anything on the computer, so seemed hesitant to do anything else. They took it for a drive and said it was fine....of course, it was cold by the time they took it out.
- Taken it to another independant garage. Same problem. Didn't seem interested, took it out later in the day when cold.
- I've personally changed the spark plugs (Bosch Platinum), regapped them from 1.3mm to 1mm.
- Changed the air filter.
- Changed the oil and filter (5w30)
- Tested all four coils by unplugging the electrics when running. Car runs as expected when removing them one by one, so seem OK.
- I have bought a Bosch MAP sensor, attempted to fit it, but it's right down under the manifold and I don't have the facilities to raise the car to get underneath and fit it from there. I also have a fuel filter which I was going to fit when doing a service on the car.
idles fine. Drives fine otherwise. Holds revs high and drops slowly after first starting (especially when warm starting) for around 2 mins.
Would appriciate any thoughts, as I don't really want to play the parts lottery and throw loads of parts at it.
Many thanks and apologies for the long post.