2001 2.2L cylinder 4 misfire

my 2.2L has a misfire on cylinder 4 that comes and goes. from what i have noticed it likes to misfire when i put a strained load on the engine or turn on my wipers. once is starts to misfire, if i don't accelerate it won't misfire but as soon as i do it starts to misfire and misfires from then on for about 100 miles regardless if i turn off the engine. also, my check engine light will come on and flash sometimes, it used to do it alot, but not so much anymore. everytime it reads a cylinder 4 misfire. i have been at a stop and have turned on my wipers and my engine starts to misfire, this has happened 4 times. it could just be sucky timing but whatever. also when i am at a stop my spedo will randomly shoot up to 10 MPH for no aparent reason. my truck is flex-fuel and misfires on both gas and ethanol. i replaced cylinder 4 injector not 2,000 miles ago and there was alot of gunk in the back of the fuel rail. do you think i need to clean out my tank. i plan on replacing the fuel filter soon. i also replaced the plugs, wires and one coil about a year ago.

Good Ac -delco plugs and wires?
I would go over secandary ign system first.
Check all ground and power feed.
Any plug wires close to computer wiring or wiper motor?
What is your fuel pressure readings?

sooooooooo... there is nothing wrong with my wipers and nothing close to the motor or anything. i have gone 2 tanks (700 miles) without it messing up until i turned on my wipers because it was raining... and it messed up... for about 30 minutes, which wasn't bad... i put in some injector cleaner and it seemed to help... could it be a voltage dampner or something eletrical messing up? i can't do eletrical, only mechanical so this is pissing me off!!! :banghead::banghead::banghead::banghead::banghead: :banghead::banghead::banghead::banghead::banghead: :banghead::banghead::banghead::banghead::banghead: :banghead::banghead::banghead::banghead::banghead:

Also check both ignition coil primary connections and grounds, as well as the injector connectors and harnesses. My gut tells me this is something electrical, not a mechanical problem with an injector or fuel pressure, but a quick check of those will verify that.

well... for 4 tanks now my truck has been running great! but i have yet to use my windshield wipers... i looked all around the motor, lines, etc... can't find anything wrong with them or any shorts at all... guess my truck is just retarded...

UPDATE!!

got new tires on the back, P235/75 R15 goodyear wranglers... and im getting around 28 miles to the gallon going about 60-65 and keeping it in 5th pretty much all the time... yippy!!