I had a problem with a hard start replaced the cap and rotor,truck starts right up now but has a light missfire all the time.thought it was a faulty cap so i replaced it again same problem.Replaced the coolant temp sensor,put new wires on (plugs replaced with delcos 3 months ago) feels more like an ignition problem than a fuel problem,when driving accelerates fine a very slight pinging, just coming back to an idle wants to idle ruff. Could this be a Ignition Control Module or the Coil going bad? Or an intake leak? Im at a loss. When the truck finally started after 5 min., before i replaced the cap it would idle fine. Any help would be greatly appreciated

1997 Chevy C1500 5.7L vortec 118,000 miles

 

It could be a leak in the intake gaskets do you know when and if they were replaced, cuz its about time with 118k for either the second set or even a third my 97 yukon did the same at 120k and it was on its third set.

 

the intake gaskets have never been replaced on this truck, reliabilty wise its only needed a starter (other than tune ups and battery) its been in the family since new. I have to put it on a scanner i guess and see what it comes up with.

 

Sounds good

 

have you checked the timing?

 

I think on that truck there is no ajustment for the timing,that its computer controlled but i could be wrong.

 

yeah, i think your right. i dont have much knowledge for those newer years where its 95% electronic.

 

I am a rookie mechanic but here is my .02

blinking ses light means STOP DRIVING as catalytic converter damage is eminent. Just on is "fix it when you can" and blinking is damage is/will be happening.

this is more than likely due to the misfire. my biggest guess would be your plug wire routing. possibly 2 switched cylinders, the catalytic converter cannot keep up with cylinders pumping tons of oxygen and raw fuel the reaction of that much of those elements is what causes them to heat up and melt down.

so yes your misfire is why your ses is blinking.

Considering the misfire was after a tuneup I would lean towards a cracked/broken sparkplug or switched wires.