My dad has a 98 c1500 with a 305 that has 220,000 miles on it. It has brand new intake gaskets, newer distributor gear, new cam position sensor, plugs, wires, dist. cap & rotor, fuel filter, etc. After driving for 15 minutes or so every morning, it starts to misfire, it doesn't throw a code, but it is def there. What could be causing this? Were stumped. Thanks

It doesn't do it till after about 15 minutes of run time.



Could this be a coolant temp sensor going bad?

 

What brand plugs are you using? I had this on my 4.3L and had to put the original delco plugs back in. Ran much better. Otherwise make sure you're running a delco cap/rotor as well and make sure the coil wire is good and not worn through. The vortec motors are notorious for burning through coil wires.

 

new wires, new delco plugs, new delco cap & rotor

The rapidfire delco plugs that I replaced were in good shape too

not sure whats up

thanks for the brainstorming though

 

my dad says it tends to do it more in the morning, so maybe its something to do with humidity?


I noticed when sitting idling today the temp guage was only reading 160* after the engine had been running for a while. thats why i wondered about the temp sensor

 

Very common injector failures.

 

yes but if it were the injectors wouldnt it run bad all the time?

 

How old is the cap and rotor? There's a TSB for when you replace the cap and rotor you're supposed to drill out the dust filters at the base of the distributor. They plug up otherwise. I had a bad cap and rotor in just 3 months after replacing it since the distributor couldn't breathe.

 

got a link?

something in my mind seems odd though since it takes at least 15 minutes before it starts doing it. Maybe it has something to do with the transition from open to closed loop?

 

Check the cap and rotor again when you perform this TSB. If it has any carbon in it, it's crossfiring again and put a new cap and rotor on. I found the best way to remove the screens was just to drill them out with my cordless drill from the top. There's plenty of room.

http://www.aatecusa.com/obdIIpro/mem...06_04_041A.pdf