Car misfire under load
 

My 2007 Honda Fit recently had the error code P0451 (Evaporative Emission Control System Pressure Sensor). Since this code showed up, the car stutters and struggles (misfire I think) around 2500 - 3000 rpm but only sometimes. Today the car was misfiring at 2500 rpm and would not go above. I stopped at a red light and all I could smell was rotten eggs. Today the error codes: P0300, P0301 and P0302 showed up in stored codes. These codes are Random misfire, misfire is cylinder 1, misfire in cylinder 2. Is this just a case of replacing the coil packs and spark plugs?

First, check that you don't have a loose spark plug. (Any slight 'poot'poot'poot' sound at startup?)

I'd plan to adjust the valve lash if you don't have any records of it being done in the past.

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Regards the EVAP code: Check that all the hoses going to the gas tank are tight. If they are, more diagnosis of the EVAP system is needed. That said, EVAPorative codes don't usually cause running problems or a limp mode.

Ignition coils might be a culprit - seems like a common malady for the Fit (mine is awaiting sparkplugs and coil replacement).

I have a misfire under load, usually around 2-4k RPMs. I've replaced all the simple stuff already coilpacks and spark plugs but it's doing it again. I'm on to replacing the MAP sensor now, haven't done it yet, I'll let you know if it helps.

PS the rotten egg smell is from your catalytic converter, the misfires are probably putting too rich of a mixture through the exhaust system.

suspicious for coil pack problem
 

When my fit started misfiring, a mechanic friend hooked up his expensive shop computer, and was able to tell me which coil pack was faulty. Replaced it with OEM part from Amazon. That was a year ago, and it has worked fine since.

The internet proposes the strategy of swapping a good (new) coil pack for each of the 4 coil packs in turn, until you find the culprit. Won't take very long. All you need is a 10 mm wrench IIRC and one good coil pack.

I guess it could also be a spark plug. Common signs of faulty spark plugs include slow acceleration, loss of power, poor fuel economy, engine misfires, and difficulty starting the car. If it's just misfiring under load, my vote is for faulty coil. You could take each one out and visually inspect. Compare how they look to a chart for visual diagnosis of spark plug problems.

i know this is an old post, but i just had the same problem except no evap code and i had no warning before i lost power in my 2009 fit and wanted to post a possible solution to anyone else looking at this post.
I replaced the Injectors, and coilpacks, and drained/flushed the gas tank and system. In the end it turned out to be the vtec solenoid.