bluebird71

iTrader: (53)

I have an '03 Silverado with a 5.3 and about 185k miles. Last year I had to replace the knock sensors and I wen ahead and replaced the spark plugs and wires a well. I always noticed a slight stammer at idle, like maybe a very mild miss. It still hasn't gone away, but its barely noticeable. Should I look into replacing the coil packs next? How long do coils usually last on these motors and are they the kind of thing that go out more and more over time, or just fail completely one by one? I really have never had a vehicle with this many miles before and have only changed coils before for performance only reasons.

1FastBrick

iTrader: (17)

When did the issue first occur? before or after the plug/wire change?

If everything checks out mechanically, I.e. Fuel Pressure, Spark, Compression

Then I would look at individual components Like the plugs.

I have had new plugs out of the box be defective or damaged because of how the parts house handled them. They will cause similar issues to what you describe.

IMO, when a coil is weak or has failed it is usually obvious and causes a dead miss which usually occurs under load. The computer usually picks it up as a misfire and reports a code. The only way to condemn a coil that is not obviously failing would be to check it with a scope.

This could also be a failed injector circuit in the ECU but you would need to identify which cylinder is suspect and test the circuit with a noid light.

You might also have a sticking injector but this usually cause a misfire or a lean code

bluebird71

iTrader: (53)

I was happening before I did anything, but it's very hard to notice unless you are looking for it. I think its maybe gotten a little better since I did the plugs/wires and a new fuel filter, but I can still feel it a little if I'm at a stop and I'm listening for it.

1FastBrick

iTrader: (17)

03 should be a return style, Have you checked the Pressure regulator at the rail?

Also have you checked the fuel pressure with a gauge?

bluebird71

iTrader: (53)

No, I guess I haven't checked any of that.