99 expy 5.4 start up

[rampcrawler]

when the truck is cold we have an intermitemt ruff start. This also causes the brakes to not work for about 1 min. then its good! The next day just a little sputter and were all good. maybe once a week the brake thing happens. replaced lots of vac lines still have problem. if you think of several things for me to check i would be most greatfull thanks

 

[metaldrgn]

When's the last time you changed your spark plugs? That is a likely cause. I don't know if that year was also susceptible to coolant leaking on the #4 cylinder and degrading the connection on the COP, but that I recommend checking it out. You will see symptoms like that without a fault code since it's firing, just with a weak spark.

 

[rampcrawler]

that a great place to start, I just replaced the coil pack on number 4 cylinder and chose not to do all the plugs there such a pain in the ass but thats where ill start THANKS

 

[splintrcel]

If your not getting brake pressure next time you start try reving the engine a bit. It should get that brake booster pressurizing. Replacing your brake booster will fix any weak brakes upon start up. If you just have crappy brakes in general is another story. If you havent swapped all the plugs you mine as well. Also order all new boots and coils and dielectric grease all the coils and plugs. Coil packs are pricey and redoing all the coil springs usually helps, it worked for me.