I have a 2003 Chevy avalanche. 5.3 four wheel drive z71. I just put a new fuel filter, cat converters, oil sending unit, new alternator, new battery, new plus and wires. My check engine light keeps flashing. My truck dies on me every time I stop or let it idle. The code reads that it has had several misfires. It has 127,391 miles on it. Somebody please help.
You changed all that but not the distributor cap and rotor? (which are relatively cheap)
WAG: Replace those. (Hey, you’ve replaced damn near everything else, might as well! The cap and rotor would be a hell of a lot more likely to cause misfires than most of what you listed.)
Since you did so many service items at the same time, it’s going to be difficult to pinpoint what went wrong and where, but I would start by checking that all the new plug wires are tight, and that none are defective right out of the package. Be sure they’re all properly routed, and not grounding somewhere. Also, since you replaced the alternator and other items, there’s always the chance that wiring somewhere got yanked loose, knicked, or damaged. A thorough check of any wiring associated with the ignition system might be a good idea, particularly where it runs beside any components you were working on.
Stop driving it until you fix it. A flashing CEL means the engine is misfiring.
Misfires can destroy cat converters in very short order.
So unless you want to buy another set of converters fix the misfire.
Since you changed both the plugs and wires you could have a bad new plug, a bad wire a cap and rotor issue or a internal engine issue.
Was the CEL flashing before you did the work? Did you route the new wires EXACTLY the way the old ones were routed? If not go fix that first.