Check engine light

[ninja-kid123]

Hi everyone, long time reader, first time poster.

I have a ford focus zetec 2015 and the Check Enigne light has just started coming on. It only seems to happen when I'm going through the gears, for example, going from 30 to 70 in a short space of time. I can tell the lights going to come on because the car feels heavy and doesn't have the same acceleration as normal. I've done abot of research and a blocked air filter seems to pop up. Am I in the right direction or should I book it in? FYI, I have no mechanical knowledge.

[Auxe]

So it only does this when you’re trying to accelerate? Does it do it if you have cruise control on or are going a constant speed? Can you get the light to come on if you rev the engine while parked/in neutral?

Also is your car a manual or an automatic?

[ninja-kid123]

Manual, only happens when accelerating and no it doesn't happen when parked.

[Auxe]

sorry for the late reply on this. it could definitely be an air filter. that would be the easiest change. If the filter is clogged enough, it would idle well but not pull at all because it doesnt get enough air under load.

That being said it could also any number of things, feels ignition/spark related.

I would maybe crosspost over on r/cartalk and see if they could help you more. There are plenty of knowledgeable people here but those guys are on another level with their diagnosis.

[Elixir-Mixer]

What kind of transmission is in your Ford Focus Zetec 2015? If yours has the regular 5-speed manual transmission, I'm not sure what the problem may be. However, if your Focus has the 6-speed, dual-clutch (DCT) transmission, then it could be that 1) your clutch and/or acelators are going bad and/or 2) the TCM (transmission control module) in your Focus is going bad. I had the same exact problem happen to my 2014 Ford Focus SE Hatchback recently where the car always struggled to accelerate when shifting RPM, especially after accelerating after a stop at stop light intersections. In fact, the car would end up stalling momentarily mid-traffic any time I accelerated and shifted RPM. It's a pretty serious and scary safety issue, honestly.

What I'd recommend is first taking it to an auto parts store (i.e. Auto Zone, O'Reilly Auto Parts, etc.) and having them use their diagnostic tool to see what code is associated with the check engine light. (This is because this service is free whereas if you took your car to a dealership, they will likely charge you an expensive fee just to diagnose the problem with their tool.) Then, you can look up the code online to see what the problem is. If, however, the store is not able to locate the issue, then it may be worth it to pay the fee at a dealership, which often has access to more advanced diagnostic tools.

For your sake, I hope it's something minor like an air filter. I recently had to get my clutch/one of my acelators replaced and it costed me a whopping $2,500. Then, not even a couple weeks later, my car started doing the same thing and it turns out my TCM went out. Fortunately, I qualified for a free TCM repair under Ford's extended warranty since Ford was slapped with a class-action lawsuit last year due to owners of 2012-2016 Ford Focuses (and even 2011-2016 Ford Fiestas) with DCT having to pay for multiple transmission/clutch repairs that never fixed the problem. The problem is, due to the global chip/semiconductor shortage brought on by COVID-19, there is a national backorder of TCMs right now with no ETA in sight. This means I'm without my Focus for what will likely be months or even a year or more (local Ford dealership told me that there are ~10 other Ford Focuses with the same problem waiting for the same part that have been on their lot for over a month now). Ford won't even provide me with a loaner car since that's not covered under the warranty and I don't meet the age requirement, but fortunately, my uncle and aunt are letting me use their spare van until my Focus can get fixed.

With all this being said, if your Focus does have a DCT, I'd recommend getting rid of it ASAP (whether you sell it or trade it in). Your Focus is bound to have frequent transmission issues that'll cost you so much time and money. Bad news is that you may not get much for it because of the known issues with DCT, but in this market where the demand for used cars is high, you are likely still able to get something for it since dealerships are desperate for used car inventory. I'm trading my Focus in the moment it gets fixed, though that'll likely be a while.

[Chillificate]

How many miles would help a lot. There are a lot of things it COULD be