QuestionQUESTION: Hello again. Im still having trouble with my blazer running roughly. I havent changed the oil yet,but could that really be causing it to run crappy? When I take it out to drive it it runs crappy and has no pick up and go. I can get it up to about 35 and then it starts backfiring really bad. I checked the fuel pressure and its only about 50. Is that good for the 4.3l vortec or should it be higher? I am really starting to get annoyed with this truck and just want to get it fixed. Also I did the test where I put it into drive and step on the gas and it does hesitate. I then unplugged each plug wire from the distributor and the only ones that didnt effect the idle was 1 and 3. I checked the plugs and they had spark. I think the injectors arent sending gas into the combustion chamber, so I replaced those two injectors and it didnt really make a difference. I was wondering if there is any other thing that I can replace on the spider injector to maybe get the injectors working completely? I am getting very annoyed and need someones help. Please help
Thanks,
Frank
ANSWER: HI AGAIN FRANK,,WELL A BACK FIRE IS USUALLY CAUSED BY A IGNITION PROBLEM OR A BACK FIRE UP THROUGH THE INTAKE IS USUALLY A VALVE PROBLEM ,SUCH AS A VALVE NOT OPENING AS IT SHOULD. BAD CAMSHAFT COULD CAUSE THIS OR ROCKER ARM PROBLEM. DOES THIS BACK FIRE SOUND LIKE A AUTOMATIC RIFLE GOING OFF,POP POP POP POP,IF SO LOOK AT THE VALVE TRAIN,1 OR MORE VALVES ARE NOT OPENING... AS FAR AS FUEL PRESSURE GOSE THIS IS GOOD. STOP LOOKING HERE...FROM WHAT YOU ARE TELLING ME YOUR PROBLEM IS STILL WITH # 1 AND 3 CYLINDERS. THE FACT IS WHEN YOU REMOVE THESE WIRES FROM THE CAP AND NO RPM DROP IS FELT,YOU GOT A PROBLEM HERE. DIAGNOSE THIS AND NOTHING ELSE. A BAD FUEL INJ WILL NOT CAUSE A BACKFIRE.. IS THERE SPARK COMING OUT OF THE DIST TOWERS ON #1 AND 3 ??? IF NOT, CAP IS BAD. IF THERE IS IS MY NEXT MOVE WOULD BE TO CK COMPRESSION ON 1 & 3. MAKE SURE IT HAS ABOUT 120 TO 150 LBS THIS WOULD BE GOOD.IS THERE IS TICKING GOING ON WITH THIS ENGINE,LIKE LIFTER TICKING ?? AS TO ANSWER YOUR QUESTION ABOUT GAS MIXED WITH THE OIL, YES THIS WILL MAKE IT RUN BAD BUT SHOULD NOT CASUE YOUR PROBLEM..GAS MIXED WITH OIL WILL FOUL PLUGS AND WASH THE CYLINDER WALLS DOWN AS I SAID BEFORE...I DO NOT KNOW THE FIRING ORDER OF THIS ENG OF THE TOP OF MY HEAD BUT IF #1 & 3 ARE NEXT TO EACH OTHER ON THE CAP THIS COULD BE FROM A CRACKED CAP. LET ME KNOW WHAT YOU FIND,, AND GET BACK TO ME,,,TOM
---------- FOLLOW-UP ----------
QUESTION: The backfiring is more like once in a while. How do I go about diagnosing the problem with #1 and 3 cylinders? There is spark coming out of the towers on the distributor and when I take the plug wires off the spark plugs they both have spark. There is no ticking going on. I just realized that the cylinders i was talking about were 2 and 4 not 1 and 3. I had them mixed up in my head. As far them being next to each other on the distributor they are, but the firing order goes 165432. The backfire is also not going into the intake it goes out the exhaust pipe.
AnswerHI FRANK,,BACK FIRE OUT THE EXH IS USUALLY IGNITION PROBLEM,SO IF 2 AND 4 ARE NEXT TO EACH OTHER WHICH I SEE THEY ARE THEY COULD BE TRYING TO FIRE AT THE SAME TIME CAUSING THIS BACK FIRE...REMOVE THE CAP AND VERY CAREFULLY LOOK AT 2 AND 4 REAL CLOSE FOR ANY CARBON TRACKING.. EVEN IF YOU DO NOT SEE IT I WOULD REPLACE THIS CAP..LET ME KNOW HOW THIS GOES AND GOOD LUCK TO YOU,,,TOM..
