Hesitation When Cold

[4x4chevymatt]

I have a 1999 Silverado with a 5.3L and about 280 000 km on it. In the morning when the truck is cold there is a severe hesitation around 2000 RPM. The engine starts to sputter and shake and If you press the gas pedal down to the floor there is nothing there. The truck does not stall and after 7-10 min of driving the problem disappears. I can accelerate at whatever rate i want and easily pass cars on the highway.

 

I have replaced the fuel filter, spark plugs, plug wires, air filter, and run injector cleaner through the engine.

 

Today I checked the fuel injector pressure and got a reading of 51 psi. I also pulled out all the spark plugs and took a good look at them. There was a slight carbon build up on all of them but nothing too serious, for the most part they appeared normal. Sometimes when the hesitation gets extremely bad I get the codes P0336 (crankshaft position sensor A circuit range/performance) and P0430 (Catalyst system efficiency below threshold bank 2) however I don't always get a check engine light when this problem occurs.

 

any help would be great, thanks in advance.

[ujtruck]

I have a 1999 Silverado with a 5.3L and about 280 000 km on it. In the morning when the truck is cold there is a severe hesitation around 2000 RPM. The engine starts to sputter and shake and If you press the gas pedal down to the floor there is nothing there. The truck does not stall and after 7-10 min of driving the problem disappears. I can accelerate at whatever rate i want and easily pass cars on the highway.

 

I have replaced the fuel filter, spark plugs, plug wires, air filter, and run injector cleaner through the engine.

 

Today I checked the fuel injector pressure and got a reading of 51 psi. I also pulled out all the spark plugs and took a good look at them. There was a slight carbon build up on all of them but nothing too serious, for the most part they appeared normal. Sometimes when the hesitation gets extremely bad I get the codes P0336 (crankshaft position sensor A circuit range/performance) and P0430 (Catalyst system efficiency below threshold bank 2) however I don't always get a check engine light when this problem occurs.

 

any help would be great, thanks in advance.

 

you have bad O2 sensor, and that also will eat your cat.