HELP: My blazer suddenly idles horribly. I dont know why

[zach78k5]

Yesterday my blazer was suddenly idling really rough. It felt almost like a spark plug wasnt firing. However, when I really stomp the pedal all the power is there. Just cruising at lower RPM it sputters and backfires a little. I opened the hood to find fuel leaking from the fuel filter housing, and a vacuum hose had come off the carb. I put the hose back on and replaced the fuel filter and took care of the leaking and the problem is exactly the same. What could it be. Plugs and wires are new and none of the wires melted on the header. Ran fine with new plugs/wires for a week.

 

[k20]

shot in the dark here, if you have headers, start teh truck, warm it up then spray a bit of water on the header pipes, whichever evaps the slowest is the dead cyl, if not, i dont know if that works w/ manifolds or not. Anyway, pull the plugs and see if any are damaged or oil soaked and therefore dead. Something internal may have occured and soaked a plug in oil, killing it. Also just double check and be sure the plug wires are on the cap and the plug good and tight. Ive had em pop off, its like wtf is wrong, o yeh, duh. Hope that helps somewhat.

 

[84_Chevy_K10]

Sounds like a vacuum leak to me.

 

[Blazer1970]

EGR valve is stuck open.

 

[4xrick]

well belive it or not even new plugs can be bad /forums/images/graemlins/rotfl.gif i would check them all and make sure they are good could also be vacume make sure all your vacume lines are good and tight and have no cracks it is usually always something little and stupid so many times I have had the same problem and it been a different thing everythime the trick with the water on the headers workss well to to find if you have a dead cylinder it is alot faster than taking out every plug.