Flashing check engine light, goes away and no code

[Mike Rose]

I own a 2004 Silverado 5.3l and have been having misfire and missing on idle and acceleration? The other day check engine light started flashing and then went away. Put a scanner on it and no code? Any clues

 

[riverbanks]

Missing low in rpms usually means air leak,test the intake manifold with some t.b.cleaner,listen for rpm change

[CamGTP]

You need a live data scanner then. Something that can watch stuff in real time. Misfires and fuel trims etc etc.

 

Check fuel pressure as well.

[Mike Rose]

Just installed a new fuel pump and it was running better for about a week. Then check engine light started flashing and went away as I was driving home. Put a scanner on it and no codes, Im stumped.

[Mike Rose]

Today I pulled and checked plugs and they all looked ok. I performed a spark test on most of the coils and noticed #3 would stop sparking at times so I suspect a faulty coil. It was a Delphi that I bought bought a year ago and the rest are original. 200k on it so I'm going to replace all of them. I did put a live scanner on it and looked a b1s1 and b2s2 voltage outputs and they were both oscillating. It doesn't do misfire data though but can read fuel trims.

[Mike Rose]

I replaced all COPs and running great again

[riverbanks]

Glad to hear,to bad the pcm skipped over individual misfire codes,went right to the 300,got to remember that one