93 gmc Sierra 1500 4.3 vortec misfiring after warmed up

[Benji]

So I replaced my intake manifold gasket on my 93 4.3 vortec, after doing so it started to run really weird once it’s warmed up, when I first start it it’ll run completely normal until it’s warm and I start driving. Then it will start misfiring so bad. I timed the distributor to 0 degrees at 750 rpm’s. I checked the code it was code 34 and 42. I assume it’s a sensor or something, but I’m not knowledgeable enough, I’ve tried pretty much everything I can think of, I just need some tips on this, thanks

 

[Schurkey]

Download the factory service manual set from the links in the Sticky threads section of this forum.

Look up the diagnostic procedures for codes 34 and 42.

 

[Benji]

Download the factory service manual set from the links in the Sticky threads section of this forum.

Look up the diagnostic procedures for codes 34 and 42.

Thanks I’ll try that