I have a 1996 Dodge ram 1500 4x4 5.9L 360 with 161,000 miles. I started having trouble one day when i fired it up then the next it ran fine then has never ran fine since. You can feel the misfire at idle but its not real bad. when i get to overdrive it shakes so bad you feel as if you was going to wreck. The cat was gutted before i bought it two years ago and has run fine till now. i replaced the distributor and the rotor and the cap and wires it ran fine the first time i started it up but the next day went back to the same way. so i replaced the coil and still no difference. i don't want to through more money at parts i don't need. i was told it was the lower intake gasket but i just wanted more opinions before i did all the work

 

My wife's 2002 Buick recently gave off multiple random misfire code's. The fuel filter was clogged, and now I think the pump is dying but anyway, the new filter cured the misfire problem on her car.

So you could check your fuel pressure.

If you haven't already done the plenum yet that be a good thing to do, there's a thread stickied at the top of the 2nd Tech Section.

If your sure the misfire is all cylinder's then check all your plugs if you haven't already, with a blown plenum the #8 plug tends to foul out pretty bad, it happened to me before too, same symptom's too, shaking and I couldn't get past 45 (clogged cat I think)

 

Edit: my phones too slow...you beat me to the reply, but oh well...

If your cat needed to be gutted, then it's more than likely because of a blown plenum gasket. Which can cause random misfires. Read the stickied plenum thread for ways to confirm its the gasket.

Also check the fuel pressure, 49PSI is what it should be around. How long ago were the plugs replaced? Pull em out, check the gap and condition.

 

+1 on plenum just fixd mine truck runS nice and smooth canT even tell its on if you have the radio up

 

The plugs were done about 20,000 ago but wouldnt see how they would all go bad at once. They are all misfiring i had it scanned and showed every cylinder plus multiple misfire. i can smell the fuel while its running at the exhaust, thats why i ruled out fuel pump and filter. i asked one of my dads buddies who is a very talented mechanic and he told me it was either to much alcohol in the fuel or it was that gasket

 

It's unlikely all of them will go bad around the same, however if they were recently replaced and un-correctly gapped, there's your problem. But that's probably not the case.

Peek down the throttle body and look for oil. See none? Take the throttle body off and check again. If there's definitely no oil leakage, vacuum test the intake. Blown manifold gaskets I'm sure would cause a misfire problem.

 

it looks like there is oil there. i am planning on tearing it down tomorrow any advice

 

I'd also vacuum test the manifold to make certain that its the gasket, or test it other ways. Oil down there can be caused by a bad PCV valve as well so...

You're replacing the plenum pan as well, correct? Changing out just the gasket will result in another blow-out down the road. You need a 'hughes engines plenum kit' or the one sold on ebay. Or the other route (not sure if this works) of cutting the old plenum pan bolts down and replacing the gasket.

Make sure to get a new PCV valve from the dealer only-they have the correct flow rate unlike most aftermarket PCV's you get at autozone, etc.

A lot of users here replace the water pump, engine coolant by-pass hose, fan clutch, timing chain/gears, thermostat, ect sensor, things of that sort as well. So I'd look into replacing maybe some of those while everythings torn down.

Advice, Uh...Don't break any intake bolts, make sure you torque the plenum pan bolts correctly following the procedure, don't drop anything (dust, debris, etc.) into the top of the engine, not sure what else.

 

I dont want to put a bunch of money in it just want it running soon cuz im getting of it

 

Should of said that in the first place lol.

I guess you can just throw in a new gasket and let the next guy take care of the next blown plenum.