2010 Honda Accord 4cylinder misfire
 

Hello Honda specialist or qualified honda mechanic.
I have an issue with a 2010 honda accord 4 cylinder. I bout it about 4 months ago car ran great when I first purchased it. I did a thorough inspection when I first saw it on the lot. I am a little mechanically inclined so I know the basics and more., but anyway after a couple of months car started to have a misfire car would hardly move nothing about 45mph. So I took it to my mechanic he said cylinder 4 misfire so I had him to change the plugs and #4 coil pack. Car ran better but fell flat on its face about a couple days later. So I decide to check a few things I ended up opening the tank and found some kind of crystalized substance. So I changed the sending until and cleaned the tank. Car ran way better 3 weeks down the road same thing happens the car does want to go. So I open the tank and low and behold some more crystalized rock. So I replace the sending unit again and cleaned the tank again. Car does great for about another 3 weeks. So then the check eninge like comes back on cylinder 4 misfire take it back to my mechanic replaces the coil pack and car runs fine again, but 3 weeks pass again and now the same issue again. Does anyone have an issue with a cylinder 4 misfire cause the vsa light to come on slows the car down. I replaced 1 injector. Is there an online fuel filter for this year model car

No inline filter on these cars. You cleaned the tank a couple times; did you run cleaner through the system? Are you using the same fuel after cleaning it or going to get new fuel (different gas station)? Are you using NGKs or similar quality? Was the injector changed on cylinder 4?

I don't know about the crystals I've never seen that before. If you've checked everything you might need to start looking further down the line manifold/VC leak or (CAT) . What type of warranty came with the car since you bought it a few months back or was it as is?

I figured there wasnt a inline filter everything is in the sending unit. The only code its throwing is a misfire for cylinder 4. Warranty is up. I bought it cash with a a 45 day extended warranty. Car runs perfect when it's doesnt throw a code. I never used the same gas when I changed the unit. I also started using 93octane on a consistent basics and used seafoam and Lucas gas treatment a couple times. Last night I switched the new injector onto cylinder 4 and took the coil pack and put it on cylinder 3 and #3 to #4 car is still hesitating and want go above 45 at 2000rpm and that's it.
If I'm not mistaking I think the plugs are denso.
One thing I started noticing is one the car is fixed and running well the car has issues wanting to start. It starts on the first turn on the key for a while and then a couple of weeks down the road I would have to crank the car 2 to 3 times. If I hold it the car will just spin over and then when it fires check engine light pops on