Engine misfiring under load - Is it my ignition coils or something else?

ignition coilsmisfireengine troubleautomotive repair

Registration:
12.07.2022
Messages: 1454

BioHacker Topic author

03.01.2025 05:19

My car started misfiring badly when I tried to accelerate yesterday, especially when going uphill. I've already checked the spark plugs and they look fine, but the check engine light is flashing, which usually points to a serious misfire. I'm debating whether I should replace the entire set of ignition coils, or if the issue might be with the wiring harness or the PCM itself. Has anyone replaced the coils on a similar model and seen improvement? I'm worried about spending money only to find the root cause is something electrical I can't see.

14 Answers

28.04.2024
Posts: 1287

Demon_C

24.02.2025 21:56

Before jumping to the coils, check the fuel pressure. Low fuel pressure under load is a super common cause of misfire that gets overlooked.

18.01.2023
Posts: 703

TetrisGod

16.03.2025 07:43

I had the exact same issue on my 2015 model. The coils were the culprit. Replacing all four gave me immediate improvement, but make sure you use OEM quality parts.

23.02.2023
Posts: 94

Angel_C

09.04.2025 17:03

A flashing CEL means it's serious. Don't just look at the plugs; check the vacuum lines too. A small leak can cause a massive misfire under load.

24.01.2022
Posts: 236

OmegaZero

11.04.2025 07:14

PCM failure is rare but possible. Have you checked for pending codes beyond the misfire code? Sometimes the PCM throws a related code that points elsewhere.

01.03.2023
Posts: 603

CyberNinja

26.05.2025 12:44

If the coils are the issue, they usually fail gradually, not suddenly under load. But if they are old, replacing them is the easiest first step to rule out the simplest failure point.

14.05.2024
Posts: 1387

Walter_C

04.06.2025 02:05

Check the fuel injectors. They can get clogged or fail under high demand, mimicking a coil failure. A professional diagnostic scan is highly recommended here.

25.06.2024
Posts: 212

Tennessee_C

04.06.2025 10:50

I think you should prioritize the wiring harness inspection. Sometimes corrosion or a damaged wire bundle near the engine bay can cause intermittent electrical faults that only show up when the engine is stressed.

18.11.2022
Posts: 176

StarBlade in response

19.07.2025 15:45

Totally agree with the fuel pressure check. It's cheap and easy to test and often solves the mystery.

05.09.2021
Posts: 1235

NukaCola

19.07.2025 21:19

I used aftermarket coils and it was a disaster. Stick to the manufacturer's recommended coils. It saved me a trip to the mechanic later.

30.01.2025
Posts: 419

GpuBurner

04.11.2025 02:04

Has anyone checked the intake manifold gaskets? If those are leaking, the PCM will read a lean condition, which causes misfires under acceleration. It's a surprisingly common fix.

23.09.2022
Posts: 949

Vasquez_J in response

17.11.2025 03:05

Regarding the PCM, if the car was recently hit or submerged, that's a bigger concern than just misfiring. Electrical damage can be tricky to diagnose.

26.07.2023
Posts: 410

BladeRunner

13.01.2026 15:51

I would start with the easiest, cheapest things first. Clean the throttle body and check the air filter. Sometimes it's just accumulated carbon buildup restricting airflow.

25.05.2024
Posts: 937

Lope_C in response

17.01.2026 03:49

If the misfire is cylinder-specific, it points strongly to that cylinder's coil or injector. If it's random, it suggests a systemic issue like fuel or vacuum.

10.10.2025
Posts: 1370

LinkHero

01.03.2026 17:53

Don't forget the oxygen sensors. If they are reading incorrectly, the PCM will adjust the fuel mix poorly, leading to misfires when you demand power. They are expensive but worth testing.

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