Auto Revving

[miked]

Engine Model : 4JG2 Bighorn (1995)

Car has been running fine until yesterday, It revs-up by itself up to 2000rpm then down to 1000rpm then goes up 2000rpm...

It emits heavy black smoke while revving up, both idle and running.

what maybe the cause of this problem Pls. Help.

I want to get an idea before have it checked by a mechanic.

Thanks

black smoke means overfuelling. so fuel system siguro. dirty filter, faulty injection pump/nozzles, etc.

kung grayish/bluish e eating up oil usually. oil rings ay pudpod na kung ganon.

ang nakakatakot jan e baka mag-"runaway diesel" iyan.

or baka nman nagoveradjust yung fast idle compensating device nyan (yung idle up sa A/C).