My reliable 1.8tdci has developed a couple of annoying issues. First is occ hesitation on the throttle mainly when dropping a gear at a junction, but then you can accelerate away, and then also when setting off sometimes it feels if its about to die. I have run injector cleaner through, and used egr cleaner. Also found the map sensor vacuum tube was broken and replaced but its still there. Fuel filter was changed 18mnths ago at 94000miles and car has now done 127500ish. Could this be the issue.

Also its developed what I can only describe as a low pitched woah woah noise that increases with road speed up to around 40mph and then fades off. Its more prevalent at 30mph, and more so turning left. Theres no clicking. Is this a symptom of wheel bearing failure, and how hard is this to sort...

The two things may not be connected. What are the tyres like? I've had many 'wheel bearing' issues/noises corrected by swapping tyres (either with the op side, or replacing with new) due to odd wear patterns etc.

The hesitiation could be due to a number of things. First of all, when you first start the car, is the idle high? and then slowly drops to normal? if so you may need to clean / replace the Idle Control Valve. It would be good practice to clean this anyway.

Secondly, you should look to clean the MAF sensor, as this could well be indiciating higher air flow than is present, or the opposite, which means the engine could be over compensating in too much / too little fuel.

As for the tyres, follow Mark's advice, swap them over (swap front and rear first, then if that shows the error is still present, swap the left and right. If the problem stays at the corner of the car, its probably bearings.

Thanks Guys

Car starts fine, idle speed is fine at approx 800rpm. I can clean the idle speed control valve, but how do you clean the MAP sensor. As said the pipe was broken but I have repaired it.

With regards to the noise, I do wonder now if its wheen balancing issues. I checked this morning after getting to work, and all the wheels apart from the from nearside have balance weights. Its possible one may have fallen off. Tyres are only around 6mnths old and are AVON brand. Wear pattern seems fine.

only reason not changed the filter, is I am a little concerned over getting the thing started again, I have heard horror stories of needing tows etc. I suppose I could always take it to the local garage, then its their problem if it wont start... MPG is still excellent, consistently around 55-57mpg.

The lack of tyre weight certainly could be a problem! your friendly tyre shop could probably balance for about a tenner.

As for the sensor, I was referring to the MAF sensor. This is the Mass Air Flow sensor (very good place to start)

If you were having any issues with the MAP sensor, it would likely return an error code of P2263 or similar. As for cleaning the MAP, I couldnt say, you would need to consult the Haynes guide.

Sorry jeebo, I cant read.... I will take the car to have the wheels checked and rebalanced if needed. Will clean the MAF sensor as well. Thanks

no worries, MAF sensor will require electrical contact cleaner (bought for around £5 from ebay or euro car parts. The MAF sensor is relatively easy to remove and then you just drown it in contact cleaner. I did this yesterday, drowned it, let it dry and repeated the process three times before putting it back together.

Just an update here. car still having hesitation, mainly on light throttle and turning... Finally got around to changing the filter, what a mare!!! Started fine first time, thought I had got away with it, then after 10mins it just died. Checked, and found no fuel at all in the filter housing and lines!?!? Finally traced the issue to the seal on the filter. We had put it on, over the filter rather than underneath betwwen the filter and housing... Took is 3 hrs to start the damn thing. The bleed pump also failed, and I had to result to putting a piece of tube over the filer outlet, and suck fuel into the filter... WHY OH WHY cant ford put a bleed pump on these things.... Also had to crack a couple of injectors.... NEVER AGAIN!!!.. Anyhow, still got these hesitations, and now stumped as to the cause. MPG after filter change a bit better, 56-58mpg over a motorway run. no sensor faults showing. Anyone any ideas at all?? Car runs fine, get the odd hesitation blip on motorway, at a constant throttle poistion... Could it be the throttle position sensor?? How would this be checked?

Could well be, the cheapest idea I suspect is to just replace the throttle pedal assembly.