My 98 Ford Ranger4.0 is having an issue when it's cold starting it's hard to start and has extremely rough idle it sounds like it's only running on 4 cylinders then after about 30 seconds to a minute you hear another cylinder kick in and then all of a sudden all of them kicking it runs smooth and never have a problem. I have replaced IAC valve,mass air flow sensor, clean the throttle body replace spark plugs and wires and it's still acts up I'm at a loss as to what it can be. I do have a check engine light that reads code 1451 which is the canister solenoid I replaced it and the problem still persists once the engine warms up and all cylinders fire it never misses a beat and she goes down the road just fine.any idea