hi i keep getting p0300 and other cylinder misfires replaced coil like 5 months ago then it started agian last month with cyl. 2 & 7 misfire replaced cap and rotor, plugs, and wires. now i got cyl. 2 & 8 yesterday. any idea of what else it could be. injectors, throttle bodie, timing?? thanks

 

Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.
http://www.obd-codes.com/p0300

 

thanks now i do some off roading and i had sucked in some water. didn't hydro lock , just got her wet. would that clog the injectors in any way?? i'm still used to carbs. havent got the injector thing yet. and if i have to replace an injector i heard you have to bleed the fuel rail, is that true?

 

and also going back to how a carb would act. it seems like the secondaries are not opening up and the mains are ok but studders at idle. only about 2 - 400 rpms thanks agian

 

What kind of condition were the plugs in?Any electrodes look burnt,fouled and what was the gap at when you replaced them.Pull the ones you just put in and look for fouling or damage=also what gap did you set them at=factory ,what type of plug,and are they the right heat range=if you have performance mods or chips or if you set the timing improperly.also do you hear any detonation at say 2000 to 2800 rpm range=like a tin can with some ball bearings in it=if so pull the pvc valve out and the oil filler cap off,put your hand over the filler hole in the valve cover and a finger over the pvc hole in the valve cover=if you feel vaccum you may have a blown plenum or intake gasket.a vaccum gauge works good too=on the lower intake vaccum hose you should have a steady 15hg of vaccum=if it's bouncing it may be timming=how many miles on the engine?also possible a sensor is giving bad info to the comp like Jo wrote above.

 

still haveing the problem. the plugs were decent,but slightly burnt, dry, still on factory gap +/-.001 . but i do hear a detonation or something. scares the sh** outta me. my main missfire cylinder is #2 but occasionally get #7 #2 #1 #8 and only them. just odd why its only that part of the firing order. but its more up in the 2800 to 3500 rpm range i get that. but sounds more like a backfire by the front right, sorta by cyl#2. but no leaks by exhuast manifold or injector and plugs are snug. i had the two piece intake manifolds gasket replaced when i got a remaned motor. less than 10,000 miles ago. trying not to go back to my mehcanic who did the motor. it seems like its minor cause as long as i granny drive it, its fine. except the sputter at idle. when i go to pass someone thats when i have issues. thanks agian

 

ok so today i think its my computer. i ohmed out my injectors and they were within 12.3 to 12.9 . today in jersey it was rain all day. and every time i got behind some one and was in thier mist trail i would start boggin out. i pulled over and my air filter was dry. (10" round filter. look more like a motor to me and needed room for my airhorns!) so i for the hell of it unpluged and reset my computer harnesses. started it up agian and drove fine for like 60 miles. and started acting up agian. does any one think i'm in the right direction with the computer???

 

If you got behind someone in the rain and it started acting up sounds like a vac leak suckin stuff in.
Also IDK what brand plugs, cap, and coil are you runnin

 

Yep!

What EXACLY did you use on the tune up?

 

ok i got a accel coil, accel cap and rotor (brass points), oem wires, not laying onengine at all. champion basic plugs, new pickup coil, put back my oem air intake setup. k&n air filter.