96 Dodge Ram 1500 5.2 liter.. Seemed to drive good till you get to 40mph and it starts bucking while the rpms go down, then comes back up and drives normal.. When coming to a slow stop, it seems it wants to cut off but doesn't, it idles ok. I also hear a small tick tick tick while idling but not driving.. Im sure the bucking is a misfire but what could be causing all cylinders to do this ? I read about the plenum gasket, fuel injectors etc, but ALL of my cylinders are misfiring. Haven't done any maintenance but an oil change as I haven't owned it long. Checked transmission fluid and there is barely any. Plugged up the scanner and got codes p300 through p308. Any idea what could be causing all my cylinders to misfire? Can post pics if need be.

 

For the misfires, what plugs are in there? These engines don't like the rare-earth fellers, standard copper plugs work the best. (brand of your choice.) Also check the rest of the ignition system, cap/rotor/wires. An excessively dirty distributor cap can cause the same behavior. Fix that first, and see if some of the other problems don't go away. Wouldn't hurt to pull a couple plugs, and see what they look like.

As for trans fluid, keep in mind, you need to check fluid level with engine running, fully warmed up, (or, at least, close to it.) and trans in NEUTRAL. Checking in park will give you an artificially high reading. And if it shows low there, then it really IS low.

 

Really? I thought P was N just with a mechanical pawl engaged?

As for OP's misfires...yes, mysterious. I'd also look at cap & rotor first and plugs. Also plug wires but there's no way all 8 wires are bad. Maybe check resistance on coil wire, though.

 

Due to the way the stock trans is valved, it doesn't charge the torque converter in park, so, checking fluid in park just doesn't work.

 

Would anyone recommend taking it to a shop like Meineke, Firestone or Jiffy lube to have a diagnostic performed ? This would tell me everything that's wrong with the truck and I could go from there right ? I wanna address the misfires as that's the only problem I have, but I've been hearing people changing their spark plugs , wires , distributor and rotor and having the same problems.. I want to avoid this, as this is my daily driver and I don't have a ton of money to pour in just to figure out the root of problem. I try to take it easy when driving not going over 40mph - 45mph and causing it to misfire but the last ting I want is for the problem to get worst.. Any and all help is greatly appreciated.

 

You can yank a plug or two for free just to verify manufacturer, material and condition. If they're not basic coppers I'd change them regardless and copper plugs aren't expensive.

Likewise a cap and rotor doesn't cost much but pulling it for visual inspection is free.....although I'm spoiled enough these days I personally insist on my topside creeper.

But no, I would NOT go to a Quickie Lube place for an actual diagnosis. But sure, if you want go to a real, reputable independent shop!

 

I would put $$ on they wouldn't be able to figure it out anyway. If they cant put a scanner on it and read the codes they are lost. If the plenum gasket is leaking it will cause the pcm to get confused and that alone will cause misfires. I actually proved this before i knew about all the issues with it. I put a timing light(see how many so called "mechanics" at the places you listed actually have one) on the individual wires and on the coil wire and found under a load(anything off idle) it will cause the pcm to fire the coil when it's not supposed to(causing the misfires). IF you verified the coil ,cap/rotor, wires and plugs are good then replace the plenum gasket(Hughes plate) You can also look down the throttle body and see if there is oil down there. I know you said you had it off but looking at it you really cant tell. When i did mine i could not find where it was leaking but it was.

 

So.. I changed my spark plugs, wires, cap and rotor. Cleared the codes and went for a drive. The misfires were gone !!! I was told that all of my spark plugs were loose so that may have been it as well.. But now I'm having another issue, not major but don't want it to develop into something bigger if possible.. So with the misfires gone, the truck drives better. Idles better, can go 70mph easy with no bucking or jerking.. but when I let go of the accelerator, the rpms dance a little bit.. I let off, they go down a little and come back up a little and do it again ( about 1-2 seconds between each) until I press the accelerator again or reach a slower speed.. Any idea what could cause this ?

 

Check to see if the 'cat' is clogged. Sounds like what you're describing. Remove the upstream o2 sensor n see if the problem changes and/or do an exhaust pressure check.

 

Will it do it while cold in P? If so I'd look at TPS. Backprobe and sweep with a multimeter for smooth movement and voltage range. Otherwise I'd look for vac leaks