My truck has been running very well, but I have been getting intermittent misfire codes. The SES light will be on for awhile, then not be on for awhile. Truck runs fine either way. I had the fuel injection system replaced, but got the same SES light now and then. I had plugs, wires, and distributor cap replaced....still same deal with the SES lights. Latest code check showed all 6 cylinders misfiring. I noticed no performance issues, despite that code check.

Does anyone have an idea of why this code would keep coming up, even though the truck is running fine?

Thank you!

 

It's not running fine if you're getting a misfire code, you might not notice it, but there is a problem. P0300, (random cylinder misfire) is almost always caused by a fault in the secondary ignition system: Spark plugs, spark plug wires, distributor cap, distributor rotor, and ignition coil. It can also be caused by low fuel pressure and worn distributor bushings. Without using expensive test equipment, the first step is to check fuel pressure and leakdown. Most auto parts stores rent/sell fuel pressure testers. When you have the tester, let us know and we can walk you through the tests.... takes about 15 minutes and no special tools, (other than the tester) are required.

The next step is make sure that it had a good tune up using AC Delco parts: Plugs, wires, cap & rotor. Don't go cheap here, aftermarket parts don't make the grade on this engine

 

I am having the same problem with my 01 blazer xtreme,random misfires , and intermitting loss of power.Changed spider injectors,tps sensor,ac delco wires,cap,rotor,double plat. plugs,cat converter ,flow master muffler ,fuel and air filter and still the same issues. My fuel pressure is 50 psi with key on and 50 psi runnning and leaks to 25 psi in 5-10 mins after turned off. Tomorrow i will replace the fuel pump with a Carter assembly. I brought the blazer cheap so i have a couple grand i can put in it.

 

If you have "a couple grand" why waste money on an aftermarket pump that will give you nothing but problems & won't last? Get an AC Delco or Delphi. Won't cost anywhere near 2K, and you'll have a quality pump.

 

If you did you home work you would see carter is made by Federal Mogal aka Moog. And if you pull the pumps from a ac delco and a carter its the same. And i paid $600 for the 01 blazer xtreme so i have some $ to put in it . I also get huge discounts for parts. As for $2000 fuel pump replacement who said that and where did that come from? Good Day to you and god bless.

 

i just had a miss fire code happen to my blazer replaced cap rote ect with delco parts still did it turned out to be my catalytic converter the insides had all fallen out replaced and all the hesitation/random miss fire went away. not saying thats your problem but give it a light tap with a hammer and if you hear rattling it could be your problem

 

Meh. I'd never buy fuel delivery parts from a company that is really best known for their suspension and steering components. I think the point that is trying to be made by Captain is that most of these trucks hit 200K or higher on the OEM pump. There is no data supporting that kind of longevity from an aftermarket pump in THESE vehicles specifically. My 98 has 200k and the OEM pump is still going strong. With that kind of proven durability, it's a no brainer as to why we replace these pumps with the same exact part that was put in them from the factory.

 

Plugs and wires are AC Delco ... fuel pump was replaced at 180,000 miles, but I don't know the maker of it. I'll look into the fuel pump possibility as well as the catalytic -- that is a part that has never been replaced or dealt with. Thanks everyone, good discussion about part quality too.

 

I tapped the catalytic with a hammer as per prior post, and there was no rattling. I have not gotten the fuel pressure test equipment, but I have been noticing it whining like crazy when it is hot, whether the tank is low or full. Two code checks in the last week came up cylinder 6 misfire.