'96 Tahoe - P0305 code

[amack23]

I took my '96 Tahoe (V8, 5.7L) with 170,000 to Auto-zone to have the engine codes checked after almost 2 years. I got P0135, P0141 and P0305. I checked out and wound up changing out the O2 sensors indicated by the codes and the codes were cleared. I changed the plugs (AC-Delco) and wires (OE-type) but the P0305 code stays. I was checking around for leaks and I noticed a whistling sound from the right side of the fuel injection (facing the truck). My next thought was to change out the distributor cap but I didn't want to keep throwing parts at it without getting some feed-back from you guys. Your input is always appreciated. Help...! I need to pass emmisons or face having my tags suspended. Thanks again.

[MT-2500]

Check for a vacuum leak on cylinder 5.
Any vacuum lines or hoses off /unplugged?
Find that whistling sound and you may fix the problem.

[amack23]

Thanks, MT. I changed the distributor cap and rotor and the whistling went away. I didn't notice any vacuum leaks. I took my truck back to Autozone to clear the code (again), and on my way home, the SES cam back on. I'm pretty sure it's the dreaded P0305 codes again. I think I'm going to take it to my mech. tomorrow to take a look at it. Thanks again for ALL your help. Thanks to you, I was able to change my O2 sensors, clear those codes and learn some stuff in the process. Thanks again MT...!!!

[MT-2500]

You are welcome and thanks for posting back with how it went.
And let us all know how it goes at the mechanic.
Good Luck MT

[amack23]

I took the truck to my mech. (gulp) and he replaced my intake gasket. It was pretty cracked up. I guess after 11 years it was time. I drove around for about an hour once he was done replacing it and NO SES light as of yet. Also, I can feel a difference in how she starts and rides. She's rides and idles extra smooth now - like she did when she was new. Thanks guys (MT) again for all your help...!!!