Hi all!

I have a challenge for probably some of the older members on the forum since there will be people posting here who were born after this car...I bought my daughter a little 2003 Fiesta 1.4 TDCi, 80k miles in 23 years, and came with a lovely little RSPB sticker in the back window from the probably elderly previous owners. Clean MOT history, all that jazz. It's not fast, but I figured a fairly basic old diesel will make a decent learner.

She's had it about 6 months now and has been having some issues with it being a bit jerky at low RPM and/or light throttle, but whenever I drive it I don't find the same thing. And recently it's been having an issue where it goes into a 2.5k RPM limp mode with "EAC FAIL" flashing on the dashboard which makes it even more sluggish.

Fault codes I've been able to pull off with a generic iCarsoft scanner were related to EGR, intake air temp, and MAF readings. I'll put the full numbers up later, the code reader is still in the car up the road.

• I checked with the same generic scanner what data was coming off the accelerator pedal (since I'm assuming EAC is Electronic Accelerator Control) and it scales well between 0v and 5v so it seems to be reading fine

• I tried some EGR cleaning spray which didn't seem to make any difference

• I had someone put an EGR blank on as a troubleshooting step before spending on replacement parts, and it does seem to have made the car a lot more driveable, but the "EAC FAIL" still happens

• I've tried unplugging the MAF and it drives exactly the same with the "EAC FAIL"

I bought a Forscan cable to see if that gave me better diagnostics and it brought up the same codes as the generic reader. But then I also tried some data logging and noticed two things:

• the MAP sensor reading is 0 kPa permanently. I read that some 1.4 TDCi don't have one, and I don't see anything at the back left of the airbox which is where I think it should be if it had one?

• the EGR duty cycle reads 9.78% permanently. Although it's blanked off as an experiment, shouldn't I still see the number change as the valve still opens and closes even if it can't pass any air through? That makes me think the valve is so clogged up that it can't even move, and that's both the cause of the EAC fail (because the valve isn't changing when the PCM instructs it) and the poor running (because it can only pass one fixed quantity of air)

I'm tempted to throw a relatively cheap new MAF on it because I should be able to DIY that, and the fact it runs the same with the MAF disconnected makes me think that could be an issue. And if someone confirms that the EGR duty cycle should be changing even if blanked then I might have to get that cleaned out. But is there anything else worth checking out? I'm keen to keep it out of the garage if possible so it doesn't end up just being a target for the parts cannon...

The three fault codes I got are

• P0401-70: EGR system insufficient flow detected

• P0113-60: IAT Sensor Circuit High Input

• P0102-70: MAF Sensor Circuit Low Input

I ended up putting a new MAF on it (the cheapest one possible on Amazon so it probably won't last forever, but I wasn't up for spending a ton on something I wasn't sure was the problem) and it seems to have improved the drivability, and I've driven it for a few hours in total since then with no repeat of the "EAC FAIL" message.

Even the two other non-MAF errors (EGR and intake air temperature) haven't come back, and Forscan is still showing no DTCs in any module.

Case closed!