eratic rmps

[buddthorn]

i have a 94 ranger with a 4.0 its driving me crazy heres why my rpms bounce all over the place causes check engine light to come on and extreme loss of power. have replaced maf o2 sensor and throttle positioning sensor has new plugs when rpms are normal runs great or if rpms are at 0 runs ok but when bouncing around it runs like crap it jurks and lunges forward even had motor replaced still does the same. also checked fuel psi was fine took it two 2 ford dealers to have dio run wont read my codes wtf. dont know what else to try i thought cam sensor but it starts just fine and was told cam sensor is eather good or bad .please help me bout to become former ranger owner

 

[Kroeter]

My 97 ranger had idling problems. RPMs jumping all over the place. I replaced the IAC valve and haven't had a problem since.

 

[06RangerXLT]

you have a vaccum leak / torn brake booster bladder.