Intermittant power loss/battery warning light/engine cutting out

[Franakapan]

Hey folks,

For the past few weeks I've been having issues with my Fiesta and I was hoping that someone might be able to offer some insight.

The most common fault is that the engine occasionally and intermittently loses power for 1-2 seconds at a time before picking up again, almost like the car is about to stall. This is usually accompanied by a loss of revs but not always.

The second fault is that the battery light pops on for less than a second and always in conjunction with engine power loss but not every time. Another light pops up on the dash... I think it's the oil light but it's so quick I've never caught it.

The final issues, which has only been happening this past week, is that when coming to a stop at a junction the engine will cut out completely, even with my foot on the clutch, after which I have to engage the ignition to restart the engine.

My local garage have no idea what the exact issue might be except that it's something to do with the fuel system (I believe that they had error codes to that effect). Having done a wiggle test on the electrics they've given the car back to me and told me to run the car until something break... So I'm on the verge of booking the Fiesta in at the local Ford garage in the hopes that their diagnostics/experience will result in a fix.

Is anyone familiar with these particular symptoms? It would be good if I could go back to my usual garage with some potential causes before taking the more expensive option. If there's a fix that I can attempt myself then more the better! I have searched various forums and websites that variously point towards crank shaft sensors, speed sensors, MAF sensors and various others but I'm having trouble matching all the symptoms.

Thanks very much,

Sam

[m1tch]

What car is it? Have you checked that the battery is in good condition, the connections are tight and that the grounding strap is good?

[fiestalux]

I had a similar sudden loss of power today but with a 2014 Ecoboost (so a different model). It does not happen very often but usually at places where I do need a sudden burst of energy, e.g. while waiting at a roundabout. Basically this morning foot down (senibly), revs, engaged clutch then no power so car went forward about 1 meter into the roundabout then cut out. Even when I put the foot to the floor absolutely nothing. I lifted my foot off and tried again and there was power - thankfully. Has anyone else had similar issues? 

[Tdci-Peter]

With these modern cars with high electronic content, all the systems are so inter-related that going from visible symptoms to a diagnosis & fix is almost impossible unless you have full access to the internal diagnostics data.

It really is worth getting a decent diagnostic system for yourself. Then you have more control, and more choice over whether to fix it yourself, go to a local, small, trusted garage, or go to the main Fraud Stealer.

The diagnostic codes are NOT always a simple, accurate indicator of the fault, the systems have to make assumptions, and are not always right. But the combination of the codes, the frequency at which codes re-occur, and visible symptoms really can help. Even if you find the codes confusing, Googling them helps, and others on this site are much more likely to be able to deduce something.

There is lots of info about diagnostic systems on this site. I have put in lots of posts about it, have a look, or I can copy it here if you want.

Peter.