Hi,

A week ago check engine light appeared, car started shuttering while in idle and while accelerating. Code diagnosed at Auto Parts was P303. Ordered a new ignition coil (Bosch) and new spark plugs (Denso) which were delivered a week later. Did minimal and very careful driving during this time, ~ 3-5 miles per day.

After replacing all spark plugs and the coil on cylinder 3, ran the code myself and now saw 3 codes: P300, P303, P304. Car feels insignificantly better WHILE driving but still has a lot of trouble accelerating/changing gears , and is still shaking when accelerating and idle.

If I try to drive up a hill or accelerate too quickly Check Engine flashes and prompts “Slow Down or Change Gears”

Any ideas? I am thinking swap all the coils, but am not totally confident it is a bad coil pack and would really appreciate some external opinions before buying the kit.

Solved: installed new set of ignition coils, almost 10k miles later still drives great, no issues.

 

First thing first, you really don't want to drive your car while it's misfiring. You're only going to hurt it. Swap your coil packs around between a misfiring cylinder and one that isn't to ensure those are not the problem.

Did the car overheat at all?

 

misfires can be caused by weak spark, incorrect mixture or compression issues. If you swap coils, inspect replace plugs while doing so. You may even want to do a compression test since you'll have the coil off and the plug out. Some other ideas: Inspect the wire harness to the coils, particularly the connectors which can crack. Check your intake air path for any air leaks/tears/cracks etc. Any oil or water consumption? Pop off the intake air hose - any signs of oil getting into the intake from the PCV?