Rough Running Need Ideas

[monkeydude3]

Hello all~
I have a 1994 XL, 4X2 with 4.0L v6 OHV pushrod and 5 speed manual trans. 135k miles. Right now my problem is the engine is running really rough. Starts up fine and it drives, but when I hold the shifter I feel it shaking really bad. Also when it idles I hear this popping "spitting" sound out of the tail pipe. When I rev it up in neutral to say about 3000k rpm, I hear it running and making the same popping noise but louder...Not sure of the cause. I'm suspecting either my timing chain or my ignition coil. SO FAR it has a new trans and clutch (6k miles on those), new front and rear brakes, new plugs, wires, new fuel injectors, all emissions parts are new except the cats, new muffler and exhaust... front end all tight... Running rough and aggrevating me... I figure the coil is starting to go because a lot of people tell me it is a misfire, which seems logical. I wonder could the coil be bad, or could the voltage to the coil be bad (a short), or could my timing chain be starting to get some significant slack, causing my valve timing to be off.... anyone who's had this problem or knows of this problem let me know!! I will end up checking all these ideas. I'm at a point where if I give up all the previous work will be wasted, and also it sure is a nice truck! thanks

take care
GEORGE

 

[MrShorty]

If I suspected a misfire like that, the first thing I would do is a cylinder balance test, to see which cylinder(s) the misfire is isolated to. On a '94, the computer is capable of performing a cylinder balance test for you (see cylinder balance test at www.dalidesign.com/hbook/eectest.html). If the computer's test doesn't indicate a bad cylinder, then run the cylinder balance test manually by pulling spark plug wires, just in case the fault is one of the injectors.