ok,,tonight i was on the highway, going up a steep hill, and as soon as i crested it, and let off the throttle peddle,it back fired through the intake really bad,,but then it drove good for about 10 miles or so, up and down hill, it started sputtering again coming down a hill with a real long straight stretch, i was just barely touching the throttle peddle. tomorrow i am going to clean out the distributor, and check and clean the cps and reluctor ring, and re-clean the maf, and check out the map....i will let you know tomorrow evening what i found out

 

Here is where i am in trying to solve this issue. When i unplug the MAP sensor and drive there is no shuttering, missing or anything. If i unplug the MAF senosr and the MAP sensor it misses and shutters bad. With the MAP sensor plugged in and the MAF sensor unplugged it misses and shutters. I did clean the MAF sensor just to make sure it was not dirt causing the problem. I don't know if my MAP is bad and that is why i am having issues or what. I am going to replace the MAP sensor and see if it works after that. I wish i were better at checking voltages, but i am not sure how to do it with the MAP sensor plugged in. I will let you know if replacing the MAP works for me.

 

didnt fix a thing !! still broke !!
cleaned/inspected and checked all voltages for map, tps, maf,,checked the power to distributor, and coil input/output, everything checked out fine,,,rechecked and cleaned all grounds,,,tomorrow i am going to check the fire at the plug, i have an inline gm spark check tool,,,,so i guess i will post tomorrow,,,the saga continues...lol

 

when was the last time you did a tune up? Plugs cap rotor wires fuel filter air filter? save yourself some grief and buy Ac Delco!

 

2 weeks ago, today,,and yes, all ac delco from the dealership...

 

Changing cap/rotor/wires/plugs is good; check also the ignition module.
I chased these symptoms (no ecu code though) for two years on my g/f's '95. Saw that EGR and IAC valves kept getting clogged with carbon, finally my neighborhood mechanic tested the ignition output and the voltage was way low.
~$35 part fixed the problem (after I spent ~$200 on multiple IAC and EGR valves). Worth checking, at least.

 

my icm checked out fine....

 

Mine did the same thing, but i have found the problem. I cleaned the maf sensor, and the egr valve and the grounds. i have also put in new spark plugs ac delco rapid fires gapped at 0.35 gap and that was the end of the po300 code. i guess these motors like hotter spark. Its runs great now. give it a try it will posibly fix yours too. I have taken mine about 500 miles so far sience and no problems