Aloha everyone, i got this car about two years ago, its a 2015 Lancer GT manual, only has a cat back exhaust and no other mods. this seems to be a really weird scenario where the car idles and runs perfectly fine, no weird revs or rpm bouncing either cold or hot both are good. Now the issue seems to occur sporadically while driving, as long as the engine is under load it will randomly cut my throttle and drop the rpms down to 2500rpm steady. i can release the pedal and press again to gain control for 3 seconds then it cuts off again. i can raise the rpms to keep up with traffic by bouncing the throttle but holding it more than 3 seconds will cut off. if i do a key cycle it will go away but return at a random time during the drive. I can depress the clutch the car will rev up perfectly fine or in neutral but once in gear and under load, the issue will arise again. There's no codes besides my airbag light from my removable steering wheel but that shouldn't be causing these problems. If anyone can help or possibly has experience with this or has seen or heard of this issue please help me, this has been going on for about 2 weeks now, i changed out my oil, transmission fluid, checked my wheel speed sensors, maf seems clean and debree free. my next thing to check would be my fuel system, or exhaust to see if the cat is clogged then lastly my throttle body area. but any of these issues would cause for a light to come on right? I'm just stuck but don't want to give up on this car.

 

I don't have any experience with the later lancers but I believe they are drive by wire. You could verify the pedal is working as expected and isn't throwing a weird value that is causing this.
The other thing you could check as you mentioned is the cat but I think that would be more consistent.

 

Would the throttle show irregularities when the car is in neutral or clutch depressed? I was trying to look at values but hard while driving at times, when the car is in neutral or clutch engaged, it’ll rev up perfectly fine and hold it more than a few seconds but once in gear, it’ll cut out almost like it has to be under load.

 

It should yea. You can check the pedal with the car off and just log the pedal. But yea, it should act up all the time I would think.
Have you checked the plugs?

 

So we did a lil further digging, ran live data as we watched the car go into the limp mode. I feel it’s more so of a throttle cut off, we could see the TPs clump as we get on the throttle and when it cuts out, we don’t let go of the throttle position but can see the TPs line drop with the rpm’s and level out at the same spot as the rpm’s. Thinking it’s possibly a bad TPs sensor where it’s dropping the valve shut I replaced the throttle body and the problem is still occurring. Though it seems to come on at random times and goes away then comes back on different inclines it seems. The throttle doesn’t drop to a specific range instead it just cuts out the throttle then hold at 3k or 2k never specific each time. It feels a lil better in torque and pull but this still didn’t correct my issue. Next is to do a catalytic converter delete. I have a test pipe with two bung holes to be welded then clamped in place. Any other ideas??

 

I would hold off on the test pipe for now and instead focus on what the live data told you. If the TPS is dropping, you need to determine if that is how these cars do limp mode or if its something else. Is this car tuned?

 

So it’s not tuned, I just replaced the throttle body that has the TPs sensor built in and recalibrated the throttle, the issue seems to be somewhat different now, it’ll randomly cut throttle off, causing the car to jerk or bounce. A few times it’s kicked the acceleration back on to where It’ll pick up. Then this morning driving to work, the throttle didn’t cut out but I did get a new check code, c1000 which is the brake switch stuck, reading up on it that could cause the throttle to cut out similar to what I’m experiencing so I pulled the plug and checked the resistance and cleaned out the switch, I should’ve tested it before cleaning the connectors but forgot, but now I know the switch is properly working gonna try and test drive the car to see if it goes into limp again.