Ford Fiesta - Intermittent engine warning light, limp mode and garage can't find the issue.

JadeHighland

Hi

I drive a 2012 Fiesta, 1.25 engine. There's an issue where ever now and again (could be weeks or a month or two apart) the engine warning light come on and I believe the car goes into "limp mode" where very little power gets to the engine. What always fixes it is turning the car off and straight back on again. I did take it into the garage last year but they couldn't find an issue and said it's one of those things that may need to get worse before they can figure the issue out. 

Yesterday, I was driving and it happened. What makes this time different is that it happened 3-4 times in the space of 30 minutes. Never happened like that before. Again, turning it on and off resolved the issue immediately. 

One thing I've noticed as well is that when starting the car, it does sound sometimes like it's struggling a little (the initial ignition). Sometimes doesn't start and again, doing it immediately after gets it going. 

Any ideas what the issue could be? 

stu12345_2

did garage plug it into a diagnostic machine to reveal fault codes

wongataa

You need to read the fault codes when it happens.  That will give you an idea of what is causing the issue.

JadeHighland

stu12345_2 said:

did garage plug it into a diagnostic machine to reveal fault codes

stu12345_2 said:

did garage plug it into a diagnostic machine to reveal fault codes

I'm pretty sure they said that's what they did

tacpot12

It seems to be an intermittent problem. Reading the fault code when it happens is probably the best way to determine the cause, but not all faults cause a fault code to be logged, and you would need to have the right equipment with you (and potentially a helper to operate it as you don't want to be distracted if you have to drive the car to reproduce the fault). 

The equipment you would need is a OBD II scanner. I use an older vGate iCar scanner and a laptop with bluetooth. The scanner can be left plugged into the OBD port, and the laptop fired up when the problem presents itself. Newer versions of the scanner are available for less than £25 on Amazon and eBay. Be care who you buy off though. There are a lot of clones, and some are no good. 

The slight problem starting might indicate a fault with the ignition or fuel flow. Has the fuel filter and spark plugs been changed according to the correct service interval? The coil pack or HT leads could also be a suspect if the cause is weak sparking at the engine. 

Goudy

Engine warning light flashes, loss of power, clears on restart and no stored codes all sound fuel/air related.

A flashing or unset engine warning light with no codes is generally a fuel/air problem, it knows there's a problem but can't pinpoint what as most fuel and air sensor readings tend to be all or nothing types of sensors.

They can read nothing or everything in their normal operation so the ecu has trouble working out what the problem is.
Sometimes, if you drive far enough without turning the ignition off and on again the fault gets worked out as it repeats enough in that one drive cycle.

One of the most common fuel/air all or nothing sensors that play up on these engines is the MAF sensor.

Something else to consider is the O2 sensor, the limp mode might be trying to protect the cat, but the O2 could be just reading an air leak.

It wants a bit more than a code read, the ecu wants logging while it's being ran, see what's going on with all the sensors.

daveyjp

Before doing anything else ensure the battery is in good health.