Massive torque dip specifically at 1500-1700rpm

Question

I have a Ford Fiesta SE from 2012, and I've had this issue for months that feels like a Damocles sword above my head. Mechanics can't pinpoint it, I'm trying here.

I have a massive torque dip around 1500-1700rpm - sometimes I drive through it and I can feel it without it being much of an issue, sometimes I shift up and end up right in that range and it's killing my acceleration entirely and it takes time to recover unless I shift back up - which has been dangerous at the beginning (now I know, but still). Some other times it's fine (though rarely when the car is already developing significant torque)...

Doesn't happen anywhere else.

I've given up on clearing the check engine light, as it comes on very quickly; reports are more or less this - misfires come and go (sometimes random, sometimes 1, sometimes 4), but the MAF is always there and the fuel leak very often. First time I see battery voltage, might have been when I briefly unplugged the battery recently to reset my radio's BT.

Note that the car has a rough idle and is really acting its weirdest when I am low in fuel (Below quarter, though I haven't been there in a while), but the above still stands when full. I must admit I used to run it to the last drops more often that I should have.

Any ideas?

Answer 1

EDIT: This answer was written before engine codes were supplied.

I’m not going to answer the question “What causes my massive torque dip” because (1) you have not provided essential information about specific engine codes and (2) you are knowingly driving a broken car (your check engine light is nearly always on) but you are not taking effective steps to repair it.

Fix all the problems that are causing your check engine light to come on, and your massive torque dip will probably resolve. If it does not, at least you will know what is good so you’re not chasing your tail and guessing or relying on hunches from random strangers on the internet.

First and foremost, you need to find a mechanic whose mantra is diagnose, diagnose, diagnose, then repair. You need evidence-based diagnosis and repair, not hunches.

You need to get past the false assumption that a particular engine code means that a particular part needs to be replaced. Sometimes it’s true, but often it’s not. You mentioned a MAF code. Sorry, no such thing. Did you mean P0101 Mass Air Flow Circuit / Performance Malfunction? Sometimes that means that the MAF is bad. Not always. The same code can be caused by a melted wire or corroded connector, a vacuum leak, a hole in an air duct, a dirty air filter, a clogged cat or a dent in an exhaust pipe from driving over a branch. If you replaced the MAF sensor but you still have the code, that wasn’t the problem and you wasted your money.

Diagnosis is not free and it’s not cheap, but in the long run it’s way cheaper than replacing random parts on a hunch, and infinitely cheaper than giving up on a repair and junking a car that “can’t be fixed” because no one spent the time to do a proper diagnosis.

Your car can be fixed. It requires a methodical approach to run down and repair each code, one at a time. When the mechanic tells you that X engine code means that Y needs to be replaced, don’t give permission unless he or she can guarantee that this will fix the code or the repair is free. That will separate the facts from the BS right away. If the mechanic isn’t diagnosing but just guessing and won’t give a guarantee, you need a better mechanic.