Hey all, I recently bought this car as a practice fixer upper from a disabled veteran. The car has 115k miles and the issue Im trying (and failing) to tackle is a misfire in cylinder 1.

First thing I did was verify the codes from the cel.

P0301 Cyl 1 misfire
P1399 Misfire in any Cyl

Secondary misfire codes:

P0302 Cyl 2 misfire
P0303 Cyl 3 misfire
P0300 Random misfire

I then verified that cylinder 1 was indeed not firing by removing the wire from the plug with no change in rpm. The other cylinders had a dramatic change in rpm when tested this way. I figured that the misfire in cyl 1 was likely causing excess load on the others, which would explain the secondary misfire codes.

I went and purchased a cap, plugs and wires, installed them and found the misfire still existed.

I noticed the old plugs had a significant amount of black baked carbon on them, which my limited research and experience tells me it runs rich. I checked with a screwdriver to see if the injectors were still operating, and I did hear the distinct ticking from all 4 injectors. Suspecting perhaps cyl 1 may be flooded from a bad injector, I swapped it out with a new injector, also noting the poor looking condition of all 4. Still no avail, the misfire persists.

Some things of note: Im not 100% certain, but when the rpms are high, ie while driving, the engine seems to run significantly smoother, although maybe thats just normal because it also is really slow to acceleration at times.

The issue is worse when the engine is hot. Cold startup at about 900rpms, then the misfire becomes more apparent over a few minutes of warmup.

The brand of plugs is ngk, wires are bosch and the cap is bosch.

Id appreciate any help guys. Thanks.