P0300 Trouble code and SES light

Hey guys, I did a search on the TC that I am throwing, and didn't find anything that was JUST a P0300. :banghead:

'99 Blazer LS 4.3L 4X4, 4 door, 125K ish.

Here are the symptoms -
driving into work today, up a slight hill I noticed hesitation and sputtering - did't act like it was going to die - just sputtering and bucking a little.
turned around - called the boss, "not showin' up today, nah nah" - drove to Advanced and got the code scanned - P0300
Picked up some new AC Delco Plats and I will be changing them out

I recently did a tune up - about 20K or so ago - and replaced plugs, wires, cap, rotor, fuel filter. Plugs were Bosch Plats, because I didn't know about the problems with them at the time - thus the purchase of AC's today ($6 each!!!)
Did a coolant flush 4K ago.
Cleaned MAF when I got home, just to see if it would help, not much.
Oil is clean and recently replaced, no signs of coudiness or milkiness.

My question is, in your knowledgable opinions (much love for this group) does this sound like a plug problem, or should I start expecting something more??? Possibly beginnings of fuel pump problems (I would have expected it just to die)? EGR clogged or blocked - is it cleanable in the '99s?

Help me please!!! :banghead: :banghead: :banghead:

Hey guys, I did a search on the TC that I am throwing, and didn't find anything that was JUST a P0300. :banghead:

'99 Blazer LS 4.3L 4X4, 4 door, 125K ish.

Here are the symptoms -
driving into work today, up a slight hill I noticed hesitation and sputtering - did't act like it was going to die - just sputtering and bucking a little.
turned around - called the boss, "not showin' up today, nah nah" - drove to Advanced and got the code scanned - P0300
Picked up some new AC Delco Plats and I will be changing them out

I recently did a tune up - about 20K or so ago - and replaced plugs, wires, cap, rotor, fuel filter. Plugs were Bosch Plats, because I didn't know about the problems with them at the time - thus the purchase of AC's today ($6 each!!!)
Did a coolant flush 4K ago.
Cleaned MAF when I got home, just to see if it would help, not much.
Oil is clean and recently replaced, no signs of coudiness or milkiness.

My question is, in your knowledgable opinions (much love for this group) does this sound like a plug problem, or should I start expecting something more??? Possibly beginnings of fuel pump problems (I would have expected it just to die)? EGR clogged or blocked - is it cleanable in the '99s?

Help me please!!! :banghead: :banghead: :banghead:


You are headed in the right direction with the AC-Delco plugs.
When you pull out the bosch plugs look real close at the ends of them you may see your missfire.
And be sure to drop the bosch plugs in the trash can or take them back and demand your money back on them.
A code P0300 just says you have a missfire.
Get the plugs in and clear codes and see what it does.
Let us know how it goes.
If it still does it post back.
Good Luck

Thanks for the quick response MT. I was hoping to hear something like this, I just hope that it clears up the problem. I will be changing them out, and I will let you know if it clears up the problem - because if it doesn't it's right back on hear to solicit more help!!..

i know the 96+ blazers also have some sort of spider injector that can leak/fail (like the damn cpi's :banghead: ). if changing your plug along with a computer reset doesn't do the trick, then i would check that spider. FAQ section has this thread about replacement if thats turns out to be the problem; http://www.automotiveforums.com/vbulletin/showthread.php?t=559014
another suggestion; a bad O2 could also cause a PO300 (i had it happen). Have u replaced them previously?

Swapped out the old (24K) plugs and put in new AC Delco Plats, properly gapped to .060. I am still having the same problem.
Is it possible that this is the EGR valve getting clogged with some carbon build up? I will pick up a gasket for the EGR this afternoon and pull it to check.
Still a little frustrated, and I hope I can find the problem soon.:banghead:

Finally found the problem!! :biggrin: :cool:
There was a misfire being caused by my "new" distributor cap between the four and five cylinders. Looking at the cap there was no sign of a problem, but had someone check it out with a full diagnostic scan and there you had it.
Lesson learned, as with Spark Plugs and getting the AC Delco's vs any other crap, go with the top shelf distributor cap from someplace like NAPA instead of what you get from Advanced or Autozone - as MT - 2500 says "do it right the first time"....:grinyes:

Finally found the problem!! :biggrin: :cool:
There was a misfire being caused by my "new" distributor cap between the four and five cylinders. Looking at the cap there was no sign of a problem, but had someone check it out with a full diagnostic scan and there you had it.
Lesson learned, as with Spark Plugs and getting the AC Delco's vs any other crap, go with the top shelf distributor cap from someplace like NAPA instead of what you get from Advanced or Autozone - as MT - 2500 says "do it right the first time"....:grinyes:

Billibong
Thanks for posting back and letting us know how it went.
Glad you found the problem and got it going good.
And a big 10-4 on the parts. Always get the good stuff.
The good oem or oem quality type parts only hurt one time.
That cheaper stuff can bite you in the rear many times.
Good Luck
MT

Yeah, I guess I learned my lesson on this one. I figured to go cheaper on a critical part and it bit me on the a$$!!