isuzu 2.6l wont idle

hey guy recently purchased a 94 model its the 2.6l one it run good but will not idle at all and back fires through the intake manifold, any idea or suggestions??

One of the main problems with these motors is the head gasket, they will go bad but not totally blow out. Check your compression thats how I found mine was bad. Also if you have the stock intake tube on it take it off and check to see if it has a hole in the bottom, it runs across the air pump rail and the heat will burn a hole in that rubber tube, now your pulling air after the MAF sensor. I had both issues on mine and it wouldnt idle worth a shit and if you cracked the throttle it would die or start backfiring. Good luck!

I need to check that on mine cause it runs fine until you go to slow down for a stoplight or something. Then the it bounces from one to two grand over and over and eventually it will calm down. Not sure what it is but havent really checked into it much yet either.

try checking the intake manifold gasket...spray some ether near the gasket area and see if it revs real high...might have a leak there...

Well, I got to messing with it and unplugged this weird looking thing with two big vacuum lines on the passenger side on the inner fender and it is running just fine now so I guess I gotta replace that when I figure out what it is or if I even need it. But so far it runs fine without it so I dont know.

Check this diagram out. If part #19 is what you unplugged, its the fast idle solenoid.   http://myisuzuparts.com/showparts.php 

The diagram didnt open. But yeah thats prob it and its hooked back up cause the truck started doing it again so I plugged it back up. Below is a pic and the red rectangle is what I unplugged.