Ford Focus C-Max, help appreciated please...

[Twiggy]

My C-max has developed a hesitation under acceleration -  it`s definitely not a mis-fire. Put new plugs in, and a dose of injector cleaner, which has made a noticeable improvement but not cured it.  It`s a 56 reg petrol 1.6 n/a, 96k miles, serviced regularly every 7.5k, and regularly returning 50+ mpg. It`s similar to the hesitation on the corsa which turned out to be both O2 sensors, but unlike the corsa, no engine light on, and nothing showing up on a diagnostic test.  Oddly, it is worse when going round a roundabout briskly... made me think it could be a poor connection somewhere ? Any suggestions please ?

 

 

[stripped fred]

Has it had a fuel filter recently?

[Twiggy]

Has it had a fuel filter recently?

 

 

 

Hmmm - where do I find it please ?                                                                                                                                                                                                                                                                                                                                                                                                          Edit: Apparently it`s a sealed for life part in the tank.   

[matty879]

possibly engine coolant temp sensor,worth checking coolant level as too low can cause misfire/hesitation,02 sensor could also be the culprit,its worth scanning it again just to see if there are any pending codes and to view the live data

[stripped fred]

Hmmm - where do I find it please ?

I don't know tbh. Just that it's worth changing if it hasn't been done as can cause issues.

[Twiggy]

possibly engine coolant temp sensor,worth checking coolant level as too low can cause misfire/hesitation,02 sensor could also be the culprit,its worth scanning it again just to see if there are any pending codes and to view the live data

 

Thank you. Oil and coolant checked every day - will check the O2 sensor and live data.

[stripped fred]

http://www.honestjohn.co.uk/askhj/answer/33679/changing-a-focus-fuel-filter

 

Looks like a pain to change. Perhaps try other suggestions first!

[Twiggy]

http://www.honestjohn.co.uk/askhj/answer/33679/changing-a-focus-fuel-filter

 

Looks like a pain to change. Perhaps try other suggestions first!

 

Thank you, will check and replace.

[sierraman]

Could be a blocked cat. I had this, chucked in some Cataclean and hanmered the life out of it and it was fine.

[Jams]

Does this have the older black top engine in? If so I would check coil packs

 

If it's the newer lump check to see if water is leaking onto the packs from the washer jets on the bonnet

[Twiggy]

Could be a blocked cat. I had this, chucked in some Cataclean and hanmered the life out of it and it was fine.

 

I put some injector cleaner in and gave it an Italian - improved a bit, but not much. I`ll try the Cataclean, thanks.

[Twiggy]

Does this have the older black top engine in? If so I would check coil packs

 

If it's the newer lump check to see if water is leaking onto the packs from the washer jets on the bonnet

 

New coil pack fitted about 6  months ago - it`s the old black top.

[sierraman]

Don't waste time with Redex etc. I was sceptical about Cataclean but it worked for me, loads more pull after I'd used it. The EML comes on from time to time about the O2 sensor mismatch but it's basically a slightly underperforming Cat, the performance of the car itself is fine now.

 

I'd clean the MAF as well. Might help.

[Twiggy]

Don't waste time with Redex etc. I was sceptical about Cataclean but it worked for me, loads more pull after I'd used it. The EML comes on from time to time about the O2 sensor mismatch but it's basically a slightly underperforming Cat, the performance of the car itself is fine now.

 

I'd clean the MAF as well. Might help.

 

Thank you - just off to get some Cataclean, and I`ll get the MAF cleaned up too.

[PiperCub]

Check the coolant temp sensor - they often fail causing the EM to think the motor is always cold so can alter the fuelling. Usually a cheap thing to replace, was often the issue with poor running Golf GTi's back in the day. Test by checking the resistance when cold then again when hot, if no/little difference - it's FUBAR so replace it. 

[sierraman]

They are not expensive anyway, yours will probably be the type held in by a clip, pull it out, expect a cup full or so of coolant to come out then whack the new one in with a bit of sealant on the seal to prevent a leak occurring.

[Twiggy]

Check the coolant temp sensor - they often fail causing the EM to think the motor is always cold so can alter the fuelling. Usually a cheap thing to replace, was often the issue with poor running Golf GTi's back in the day. Test by checking the resistance when cold then again when hot, if no/little difference - it's FUBAR so replace it. 

 

Thank you - will try that.

[New POD]

Could be a blocked cat. I had this, chucked in some Cataclean and hanmered the life out of it and it was fine.

 

the ceramic inside the Cat on a mk3 astra I had once, was loose and as you accelerated to 4000 rpm it rotated and blocked the exhaust.  You could head it rattling about on idle though.

[sierraman]

Sometimes they do break up, you can easily see if it's that though.

[Twiggy]

Thank you for all the tips and suggestions. I was thinking about the "good" old days, when I actually understood what was going on under the bonnet.................... Whenever I got another car, the first thing I always did was to change the oil and filter, the plugs, plug leads, coil, condenser, points and distributor cap. I don't think it ever failed to improve  the running. I put a new coil pack on the C Max 6 months or so ago, and new plugs a couple of weeks ago, followed by some injector cleaner and cataclean, all of which did improve but not cure the hesitation. So................. I thought I`d put new plug leads on (the only thing left to change on the ignition side of it) and asked the garage to order some good `uns. He seemed a bit reluctant because they are very expensive, and he said that they HAD to be O. E. OK........  he got them for me, and I fitted them................ problem solved. It is now running like a new one. Been out today, Romsey to Rhayader in mid Wales then up the Elan Valley almost to Dollywobbler country. A lovely run apart from getting lost in Monmouth (and Monmouth is a lovely wee place) 373 miles at 52.9 to the gallon. I`m a happy chappy !

[Twiggy]

How do I change the title please ? ? ?