Twiggy Posted June 4, 2017 Share Posted June 4, 2017 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 ? Link to comment Share on other sites More sharing options...
stripped fred Posted June 4, 2017 Share Posted June 4, 2017 Has it had a fuel filter recently? Twiggy 1 Link to comment Share on other sites More sharing options...
Twiggy Posted June 4, 2017 Author Share Posted June 4, 2017 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. Link to comment Share on other sites More sharing options...
matty879 Posted June 4, 2017 Share Posted June 4, 2017 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 Twiggy 1 Link to comment Share on other sites More sharing options...
stripped fred Posted June 4, 2017 Share Posted June 4, 2017 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. Link to comment Share on other sites More sharing options...
Twiggy Posted June 4, 2017 Author Share Posted June 4, 2017 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. Link to comment Share on other sites More sharing options...
stripped fred Posted June 4, 2017 Share Posted June 4, 2017 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 1 Link to comment Share on other sites More sharing options...
Twiggy Posted June 4, 2017 Author Share Posted June 4, 2017 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. Link to comment Share on other sites More sharing options...
sierraman Posted June 5, 2017 Share Posted June 5, 2017 Could be a blocked cat. I had this, chucked in some Cataclean and hanmered the life out of it and it was fine. Link to comment Share on other sites More sharing options...
Jams Posted June 5, 2017 Share Posted June 5, 2017 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 Braddon81 1 Link to comment Share on other sites More sharing options...
Twiggy Posted June 5, 2017 Author Share Posted June 5, 2017 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. Link to comment Share on other sites More sharing options...
Twiggy Posted June 5, 2017 Author Share Posted June 5, 2017 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. Link to comment Share on other sites More sharing options...
sierraman Posted June 5, 2017 Share Posted June 5, 2017 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 1 Link to comment Share on other sites More sharing options...
Twiggy Posted June 5, 2017 Author Share Posted June 5, 2017 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. Link to comment Share on other sites More sharing options...
PiperCub Posted June 5, 2017 Share Posted June 5, 2017 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. Twiggy 1 Link to comment Share on other sites More sharing options...
sierraman Posted June 5, 2017 Share Posted June 5, 2017 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. Link to comment Share on other sites More sharing options...
Twiggy Posted June 5, 2017 Author Share Posted June 5, 2017 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. Link to comment Share on other sites More sharing options...
New POD Posted June 6, 2017 Share Posted June 6, 2017 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. Link to comment Share on other sites More sharing options...
sierraman Posted June 6, 2017 Share Posted June 6, 2017 Sometimes they do break up, you can easily see if it's that though. Link to comment Share on other sites More sharing options...
Twiggy Posted June 13, 2017 Author Share Posted June 13, 2017 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 ! Dave_Q 1 Link to comment Share on other sites More sharing options...
Twiggy Posted June 14, 2017 Author Share Posted June 14, 2017 How do I change the title please ? ? ? Link to comment Share on other sites More sharing options...
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