My engine has been misfiring and throwing codes left and right since it started getting hot out.

I have checked the codes, most of which point to cylinder 5 being the culprit, even though I have replaced the cables, plugs, and coil pack.

I have checked and cleaned my intake, MAF, and installed a K&N air filter, and installed all new vacuum hoses, and I am thoroughly stumped as to what could be causing this.

The problem is intermittent, and really only starts up when it is >80 degrees out, and only after the engine has warmed up (though it does start like crap sometimes).

The misfiring has gotten really bad of late, with some really bad hesitation and near-stalling in stop and go traffic. It used to only misfire maybe once or twice on a hot day, but now its nearly every time I drive, and usually 5-10+ times per commute (17 miles).

The only thing that I can think of that MAY have caused it to become worse is I have added some Lucas to my fuel on the last fill up.

Does anyone have a clue what could be causing the misfiring? I'm going nuts here!

 

Happened to mine put high octane and than add a bottle of 108 octane Boost from autozone. Then run the car hard for a day of two and it will fix it

 

It was so bad in mine that the check engine light would come on and flash. You might have to run it with octane boost for like a month till it runs right again. Mine was saying 1 and 6 were misfiring not it runs perfect. But my turn signals just stopped working but the hazards still work. I'm stumped this time and im on my 2nd waterpump and 3rd tierod