I been having this problems for about two weeks. When i shift to first gear an i rev it up it would hessitate an when i hit about 2700rpm it kicks in an gains all the power back but when hitting 4700-4750 its start to miss an back firing am it would have trouble gaining speed at this rpm range. When shift to another gear a cloud of black smoke comes out the exhaust an it does it every gear an fuel comsumption is really bad. I have replace a lot of things an still have the same problems things i have replace Timing Belt, water pump, dist. rotor, dist. cap, spark plug wires an spark plugs, fuel filter, air filter. I have check the cylinder compresion on the engine an it all came out around 149 to 152psi all of the injectors are working an i tried pulling the ecu code an only the a/c code comes out, tested the ignition coil an ignition control module an they came out good, also tested the maf sensor an came out good too i have replace all the vaccum hoses an the pcv valve i just ran out of ideas fuel pressure is good an fuel pressure is working good. Some one suggested me dat it might be the cat-converter clogged up but i havent checked dat yet any help would be appriciated.

 

timing sounds off or fuel pressure could be wrong.

 

the ignition timing is set to 20 degress BTDC ill double check everything an the fuel pressure again. thanks ill keep u posted about it

 

What heat range plug are you using?

 

I have NGK Iridium spark plugs its says heat range 6