Backfiring above Idle

[Elevator Man]

I started my blazer sunday morning after driving it all saturday night without any problems. It is really cold natured and I probably should have let it warm up but I was in a hurry. I got a little ways down the road and it started backfiring really bad, and alot. I havent had a chance to look at it yet, but I was looking for some advise on where to start. THANKS IN ADVANCE!

 

[Disciples Performance]

how old is the motor? check timing again? dizzy might be messed..

 

[Elevator Man]

I don't know how old the motor is it was in the truck when I bought it 3 years ago. It was crazy that it just started all of the sudden.

 

[Disciples Performance]

does it go away when the engine is warm? also is it still doing it currently ?

 

[Elevator Man]

It warmed up pretty good sunday I have't had a chance to look at I left it at my farm 30 miles away. I was just thinking about where to start and what kind of parts to take with me.

 

[Elevator Man]

Did I mention its backfiring through the carb? (If there is anyother way)

 

[dbabicky]

I started my blazer sunday morning after driving it all saturday night without any problems. It is really cold natured and I probably should have let it warm up but I was in a hurry. I got a little ways down the road and it started backfiring really bad, and alot. I havent had a chance to look at it yet, but I was looking for some advise on where to start. THANKS IN ADVANCE!

If your timing is good to go, go to www.bob2000.com/carb.htm That is if your carburated. I for got to look @ what year your driving.

 

[Elevator Man]

Its got a q-jet and its and 80'ish 305

 

[dbabicky]

Yea, check that website, he's some good info on Q-Jets and just carbs all together, and it's free!!!

 

[Elevator Man]

Thanks a bunch I'll check it out!

 

[Disciples Performance]

def timing issue sounds like... 180 out

 

[bigbadchev84]

choke? was it running fine before? did you do anything?

 

[mxfireman]

If your timing is good to go, go to www.bob2000.com/carb.htm That is if your carburated. I for got to look @ what year your driving.

Thanks for the web site, I think I found my carb problem.

 

[dbabicky]

def timing issue sounds like... 180 out

Could very well be a timing issue. Don't see how he could be 180 out since he didn't touch it. He just went out and started it. Could have jumped a tooth,COuld be ignition, dead plug,wires, ect.ect. Just the carb is a place to start and they're easy to check . Alway's start cheap and simple then progress down the troubleshooting tree.

 

[K5dreamer]

yeah, when something goes suddenly like that, my first impulse is to check the plugs, then the wires, then the cap and rotor. if the plug wires burn, or crack, they will short to anything metal near them. look for discolored spots on the wires near metal surfaces. look at the cap and rotor for excessive carbon build up, or black lines indicating cracks that could lead to shorts. same thing on the spark plugs, look at the white porcelin insulators for black lines. cracked insulators will cause shorts and lack of spark.

 

[Elevator Man]

I have checked out everyting. I checked plugs, wires, timing, rotor, cap, everything I could think of. Someone told me that it could be sucking air between the intake and carb so I put a new gasket on. There are not any vacume leaks that i can find. If I slowly bring up the throttle it does not backfire. If you give it throttle fast it backfires like crazy. There are alot of vacume lines pluged on th carb and there is not much vacume if any. I'm wondering if this could be a vacume advance issue??? Or maybe its a carb issue. Please help. I'm out of my mechanic boundries.

 

[Elevator Man]

backfiring/leaking gasket???

Could this issue be an intake or head gasket, could it be sucking air and making the fuel/air to lean??? I gotta get this thing running please help!!!

 

[Thunder]

Timing gears/chain? How mant miles on the engine?

 

[onetonbb74]

If I slowly bring up the throttle it does not backfire. If you give it throttle fast it backfires like crazy.

judging from this statment, im gonna say accelerator pump in the carb, either dumping fuel, or has a plunger leak with debris and is not pumping enough fuel. Plus the timing is off and the vaccum advance probably is stuck or not working at all. Pull the cap, and see if the vac. adv. is hooked up and is not all jammed up. Put a vaccum guage on the carb near the baseplate and it should be around 18 with a stock 305. Adjust the carb until you get the most vaccum as possible. if your vacumm still sucks, like at 6-11hg, then there could be a possible intake vacumm leak or a head gasket compression leak by the 2 middle cylinders.