running rough, any ideas ?

[rab]

started running rough today after a 30 min run home from riding trails .. usually sweet as hell but felt like it was running on 5 cylinders(is running on 6 just feels like 5), but checked all plugs and all getting strong spark and no untoward noises (tappets/valve train etc).. plain weird.. any idea's ? are there any common issues ? it never misses a beat and starts off the button first hit every time no matter how long its been sitting..

4.0L fuel injected 94 Xg ute

any ideas on sensors or what may cause this ?

[stav50]

i would suggest a vaccum leak, check the hose to the map sensor.

[rab]

actually turned out to be a broken blade on viscous fan ! was making it unbalanced and causing the bibration... strange but true !