Ok so here is whats goin on. I have a 98 Blazer Mark III edition. 4.3L 4x4. 111K miles. Before the winter it drove from Rochester to Buffalo (90 miles or so) with no problems ran like a top. Got parked for the winter due to some licensing issues. Sat all winter at a friends house outside untouched (i know im an *** for not starting and moving it) got everything taken care of and got plates and insurance on her. As soon as I drove out of his driveway it had no power, bogged down around 2K RPM, couldn't go over 30mph. Got it home. Oil changed right away, replaced fuel pump, fuel filter, plugs, wires, distributor cap, air filter. Still had the issue. Found a vacuum line that was flat when the vehicle was running. Replaced all the vacuum lines, ran awesome for about 45 seconds. then same thing, started bogging down right away. CEL is on. Code that came up was P300 random multiple engine misfire. The egr code came up as well. i am almost at wits end with this truck, but refuse to part with it. I am thinking maybe it is time to go and drop it off at either a local shop or a dealership and just have it fixed. There is not much else that I can find to be replaced. Any ideas or hints of what to look for would be awesome. Thanx

 

A couple possibilities come to mind immediately considering the sitting and the code along with what you have already replaced.

Bad gas from sitting all winter perhaps?
Make sure you have filled the tank with fresh fuel and add some fuel system drying agents as you no doubt have some water in the tank after sitting all winter.

Fuel pressure regulator, and or fuel injector spider assembly.
Both are common causes of that code on these engines.

Though it could be a few other things as well considering that you don't have a specific cylinder code.

There is literally hundreds of pages worth of information about that code on the forums here. Including exactly how to test just about every known cause. I would recommend using the search function to find some more information about it before taking it to a stealership.

 

Absolutely YUP!

Get Factory Shop Manaul, or Mitchell's online, or AllData, or go to a local mechanic, and get them to printout the repair diagnostic flow chart for your code.

Read it until you understand it, and ask questions. Then, if you don't or can't do the repairs, you can still tell mechanic/dealer EXACTLY what part to repair, instead of your wallet subsidizing a fishing expedition UH HUH.

EVEN IF YOU DO KNOW WHAT'S UP, YOU CAN GET TAKEN. I told a dealer once to replace the famous ignition solenoid, as per the TSB (which they said they didn't know about - see symbol below), and they asked me for 10 MINUTES A BUNCH OF QUESTIONS LOOKING FOR EXTRA $$$/repairs. I told them if they couldn't write up a service order to ONLY replace one part, then I'd clear out.

They took me for 3.5 hours of labor, bogus related stuff, and a $326 repair bill. The next week, I saw that the TSB by the Factory gave dealers 0 .7 hours to do the repair. I went back, showed it to them, and held out my hand. All I got was the shaft, and a door bushing set. They're professional snow jobbers, and beat me at MY game.

No more of that stuff NOPE...

 

ok so heres what i found out. The spider injector dumped on me. so now I am getting another one from a buddy of mine that blew his tranny, his truck runs perfect cause he just did his so on top of all that, i found out the rear end is bad so i am replacing this as well. (also obtaining from my friend) i am shelling out 250 for everything, plus getting some more odds and ends that i need to make this baby complete. I will post some build pics to add to the thread so that it may help out with someone else who is stuck where I am. i am really aggravated with this whole ordeal, but fixing my blazer is still cheaper than the work i would have had to do on my expedition. (which now is someone elses headache.) thanks for all the input guys and i will post some follow up stuff when I am done.

 

ok so now i have replaced the spider injector, fuel lines, egr, maf, new throttle body, new plentum. she runs great, until i try to step on it or take it above 2k RPM. It just seems like all the cylinders drop out on me. i really dont understand whats causing this, and now on top of it my silverado is acting up, but thats another story for another day.

replaced : spider injector, fuel lines, fuel filter, dist cap, wires, plugs, fuel pump, plentum, egr, maf, new air cleaner, new vacuum lines, new rear end, had the fuel tank cleaned and blown out to get all dirt and grime out. im pullin my hair out. not sure where to look next. anything would be appreciated.

 

What testing did you do that lead you to replacing all of those parts? Surely you did some testing...

Have you tested the FPR? Looked at O2 sensor output with a scan tool? What are your STFT & LTFT values for both cylinder banks? Have you done any live sensor readings while the problem occurs?

 

Try cleaning your Mass Air Flow sensor. It can bog you down when its dirty espesially since it sat for a good period of time.

 

Testing your TPS sensor would not be a bad idea either.
I do hope that you are testing parts before replacing them rather then playing shotgun mechanic.

 

as far as testing, I did a preliminary test of the fuel pump by testing for pressure at the valve, when i first got the truck home there was no pressure. Upon doing research as to what I should look into because the vehicle sat for so long, I came across a friend who had a parts truck, so I replaced what I could with no cost at all. I did have to purchase fuel lines, vacuum lines. When I replaced the injector, I took the plentum off to look inside and #3 was clean (as opposed to the dirty carbon look that is supposed to be there) so I knew the injector was leaking. The egr was really nasty looking, so I replaced that as well. The MAF, was replaced fresh on my buddy's truck so he just gave me everything from the plentum back. His top end looked much nicer than mine. I havent had a chance to do a live value check since I can't get this damn thing to run for that long. Today I am thinking about giving it another try, I have access to a global computer so I may try to snag it today and get things going. I am also going to do a fuel pressure test, ive heard that even if the pump drops a couple pounds, it will idle but not run when pressure needs to be increased. The fuel pump came out of my buddy's truck and is under warranty still. Maybe his pump got clogged because his vehicle sat for the coldest months of the winter, but was in a garage and away from all the snow and crap. If there is anything I haven't covered, please let me know. i am pretty good with the older OBD I blazers, but this new computerized stuff is kinda confusing. The most recent code I got again was the p300 (random misfire) but it only misfires under load after 2K......

 

So heres an update, patched a hole in the gas tank, new filler neck, gas lines are in great shape. Idles perfect, bogs down at 2500 now instead of 2000. Replaced the pick up sock in the gas tank, fuel pressure is perfect, no loss at all. NEW SYMPTOM: upper radiator hose gets hard as a rock within minutes, temp is normal, this truck is really really weird. no coolant in the oil and vise versa. water pump functioning great, compression on all cylinders is good, valves are in great shape, distributor is in great shape, coil is good, plugs are dry. IM GOING CRAZY.....Please Help