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helmstetler
Novice
Dec 14, 2010, 7:43 AM
Post #1 of 2
(3849 views)
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96 S10 Blazer Backfiring
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I have a 96 Chevy S10 Blazer, 2w drive, 4.3 L SFI with 132000 miles on it. It has been backfiring. All of the symptoms pointed to a fuel pressure regulator as it would start after a few tries and would not backfire at the higher speeds; eventually, it stopped starting all together, but would start instantly with starter fluid sprayed into the a small hole I drilled into the plastic air duct above the throttle body and after it started I plugged the hole with a small screw. So, I then replaced the fuel pressure regulator. It now starts up after just one or two tries and idles better, but it still backfires, especially on deacceleration. 1st question, after I replaced the Fuel Pressure Regulator, should I have the computer reset to default to relearn or align with the insertion of the new fuel pressure regulator?
After I reach about 30 miles per hours it purrs like a kitten, unless, of course, if I deaccelerate. Before replacing the fuel pressure regulator, previous codes showed the possiblility of a blocked cannister vent valve and an EGR with the pindle at only 10% of where it should be. 2nd Question, all my reading tells me that an EGR valve or evap system will only affect an engine at idle; can the evap system actually cause the backfiring and stuttering that I am experiencing? 
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Sidom
Veteran
/ Moderator
Dec 14, 2010, 9:16 PM
Post #2 of 2
(3841 views)
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Re: 96 S10 Blazer Backfiring
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It's really kind of hard to give a guess due to pretty much all the info provided is conclusions drawn from test data we can't see. Personally I like to be able to draw my own conclusions.
Backfiring is usually a timing issue meaning that the combustion is happening (or happened) at the wrong time. This could be electrical or mechanical.
A few basic tests would be in order to check the mechanical condition of the engine and to make sure the secondary ign is in decent shape.
A vacuum reading @ cranking, idle and cruise would help to make sure the engine is in good shape. scoping the secondary would help verify the ign. I realize most folks don't have a scope at home so you would be limited to a visual inspection of the plugs, cap & coil. If there is any question at all change them out. Due to the poor cap design I would be tempted to put on an OE right off the bat if I didn't have a scope just so there would be no questions about it and a ton of time wasted.
A fuel pressure reading is really needed on this one as well due to the poor design & problems with the fuel system....
Also pull the codes to see if there is any help there....
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