Error Code P0303 #3 Cylinder Misfiring

[bent]

My 1996 GMC 1500 Sierra overheated and blown out the back of the intake manifold gasket. Replaced gaskets but now getting a code P0303. Replaced rotor and cap also spark plug and wire for cylinder and getting spark. Idling rough but running good at speed. What else could be the problem?

[bent]

Vacuum leak at the intake manifold near the #3 cylinder.

 

I just change the intake manifold gaskets, It was idling rough before I tore it down. Someone told me on another site it might be a clogged injector and I need to have it professionally cleaned because that year has a problem with the poppet vavles sticking closed. What do you think.

 

Thanks Brent

 

Do you have a multi-port injection system or a TBI engine...TBI means you would have a lot more issues than just a misfire on cyl 3.

 

 

They call it a Multi-point injection fuel system so I'm not sure if it is a multi-port or a TBI System.

[Silverado4x4]

On top of your intake do you have what looks like a carb with 2 injectors side by side? If you do then its a TBI. What motor do you have V6 or V8?

[bent]

On top of your intake do you have what looks like a carb with 2 injectors side by side? If you do then its a TBI. What motor do you have V6 or V8?

 

I have a Vortex 5.0 it has 8 seperate injectors like this.

[Nytemare]

Vacuum leak at the intake manifold near the #3 cylinder.

 

I just change the intake manifold gaskets, It was idling rough before I tore it down. Someone told me on another site it might be a clogged injector and I need to have it professionally cleaned because that year has a problem with the poppet vavles sticking closed. What do you think.

 

Thanks Brent

 

Do you have a multi-port injection system or a TBI engine...TBI means you would have a lot more issues than just a misfire on cyl 3.

 

 

They call it a Multi-point injection fuel system so I'm not sure if it is a multi-port or a TBI System.

 

Yeah...mulit port...multi point...same difference....you have 8 injectors...not 2 is what I was getting at.

Yeah you could have a sticky injector.

I would clear the codes, re-torque the intake manifold and try it again to make sure its not just something silly like you forgot to properly torque a bolt or something.

[thearborbarber]

Vacuum leak at the intake manifold near the #3 cylinder.

[bent]

Vacuum leak at the intake manifold near the #3 cylinder.

 

I just change the intake manifold gaskets, It was idling rough before I tore it down. Someone told me on another site it might be a clogged injector and I need to have it professionally cleaned because that year has a problem with the poppet vavles sticking closed. What do you think.

 

Thanks Brent

 

Do you have a multi-port injection system or a TBI engine...TBI means you would have a lot more issues than just a misfire on cyl 3.

 

 

They call it a Multi-point injection fuel system so I'm not sure if it is a multi-port or a TBI System.

 

Yeah...mulit port...multi point...same difference....you have 8 injectors...not 2 is what I was getting at.

Yeah you could have a sticky injector.

I would clear the codes, re-torque the intake manifold and try it again to make sure its not just something silly like you forgot to properly torque a bolt or something.

 

 

Yeah, the new sparkplug in put in number 3 shows that it's not even burning at all but it has spark.

[bent]

Vacuum leak at the intake manifold near the #3 cylinder.

 

I just change the intake manifold gaskets, It was idling rough before I tore it down. Someone told me on another site it might be a clogged injector and I need to have it professionally cleaned because that year has a problem with the poppet vavles sticking closed. What do you think.

 

Thanks Brent

[Nytemare]

Vacuum leak at the intake manifold near the #3 cylinder.

 

I just change the intake manifold gaskets, It was idling rough before I tore it down. Someone told me on another site it might be a clogged injector and I need to have it professionally cleaned because that year has a problem with the poppet vavles sticking closed. What do you think.

 

Thanks Brent

 

Do you have a multi-port injection system or a TBI engine...TBI means you would have a lot more issues than just a misfire on cyl 3.