Stumped on hesitation problem

[matt sorrentino]

hello guys my 94 c1500 350 TBI keeps having hesitation and stumble problems under light load with a cold engine. When taking off from the light it wants to choke and bucks bad.

I have tried to tackle this issue with research of common issues but no luck.

So far I have replaced/checked:

New IAC
New TPS new cap and rotor, new coolant temp sensor(by the thermostat),new MAP, new wires and spark plugs, new fuel filter.
Tested egr valve, fuel pressure, tested injectors, rebuild the TBI unit(rebuild kit) checked for vacuum leaks.

What else could I check?

Any ideas help is greatly appreciated

 

[skylark]

Check your base timing. Sometimes as the timing chain and distributor gear wear causing the base timing to shift.

 

[matt sorrentino]

Check your base timing. Sometimes as the timing chain and distributor gear wear causing the base timing to shift.

Thanks buddy I'll check that as soon as I can!