Dear all

I did a 135 mile each way trip yesterday and my trusty “T” reg Focus began to cough and splutter during the last 3o “ish” miles. The tank was full except for around 70 miles of fuel. It was still running, but very strangely as the engine would not rev. I couldn’t pull away quickly in traffic, I had to roll gently and quickly change to a higher gear, then next gear etc. and eventually I’d get to 60/70mph and cruise with no problems …. Until …conditions made me loose speed again or I tried to accelerate and then I could feel the engine missing.

Here’s the strange bit – I stopped in a lay-by jumped out and played a hunch, I unlocked the fuel cap and released either pressure [more likely a vacuum] which the tank appears to get, usually issues only occur over the last gallon or so when it coughs around when heavy cornering and wants filling before the low fuel indicator comes on. Once the fuel cap is released it seems to be OK for the remaining fuel in the tank. Anyway, yesterday once I had released the cap the engine would rev to 7k without a problem and pull away just as if nothing had happened. To my reckoning there were only two things which might have been brought into play – 1) the fuel cap - pressure/vacuum issue and 2) to do this I had to switch the engine off to unlock the fuel filler flap, did this reset the ECU or have other effect?

The issue was repeated on the journey home at around the same mileage +/- although not quite as badly – there was a difference in ambient temperature and on the return route not the stop start in very heavy traffic on an Easter Monday. About 30mins after arriving home I did another short journey of 10+miles in each direction and the engine never missed a beat.

I’d very much appreciate any pointers you may have on where to start looking to solve this one, please.

TIA

RobO

 

Either the coil pack,most likely,or the head gasket unless you filled it with diesel

 

Thanks for taking the time out to reply.

I'm not sure about the coil packs, never had a car which has had coil pack trouble before, so maybe a good place to start looking!

** Does anybody know where the tank breather is situated? - wondered if that might have got blocked / trapped and not allowing the tank to vent properly causing a vacuum? I assume it must have one? **

The only other info I have is that it is the first long run it's had in a while and when I filled up at TESCO the tanks were being filled up at the same time and I just wondered if there was an outside chance this might have kicked up some sludge in their tanks which in turn I might have picked up blocking; restricting flow to the fuel filter. I would have thought that most unlikey though as I would have thought that once the filter is blocked it stays blocked until changed.

 

hi i got the same prob tried fuel cap for pressure worked for a bit,new filter no difference, not sure if its tps,crank,temp,cam sensor if you cure yours let me know and vice versa from stuart

 

m got worse over the past few days i put another tank and fuel pump and and so far it seems to have cured the problem

 

Hi Stu
Sorry to hear that you've had further problems! Other than what I've experienced for some time in terms of what I'll describe as a "vacuum" in the tank only occurring when the tank is low and causes hesitation on cornering - provides an inrush of air when the fuel filler cap is removed, I've been OK even yesterday when ambient temperatures got very high - was out Photographing on a Vintage & Classic Car Run. I've put the "low tank vacuum" scenario as possibly a blocked carbon breather??? [Still haven't changed the fuel filter]. Your solution seems a bit drastic, but if it's worked well done - we'll see how it goes and hope for confirmation of a positive outcome.
Did you check the old tank for particle build up and check the fuel pump -[run up dry]? I'd have thought more in terms of a wiring connection rather than an intermittent pump - possible poor grounding; better result on wet days? Just a couple more thoughts .....
Rob

 

MAF could also be the culprit of this, my focus spluttered, wouldnt accelerate properly. i also pulled over waited a while and then the car would drive again normally for a short period of time and then it would start missing again.

 

hi i have recently converted my 1.6 cvh engine mk4 orion to a 1.8 fiesta zetec engine using the fiesta ecu and loom wired into my own loom car starts fine but as soon as the engine warms up and you try to drive it it starts splutering and losses power to the point where it hardly moves when you press the accelerator to the point where it tries to cut out help me please