Im new here so please be kind. lol
I have a 98 ram 1500 with a 5.2L that is about to put me over the edge. This truck defies everything I know about engines, I actually am an old school guy, carbs, headers, heads and cams to make engines run. This computerized stuff is somewhat new to me. Anyway here go's.....When I start it up cold all is good, runs great. But about 20 miles down the road it starts to miss, always on cyl. 1, 2 and 3. At first I didnt know which cylinders were missing so started out by replacing the plenum gasket. It needed to be replaced but didn't fix the prob. So replaced crank pos sensor, cam pos sensor and IAC valve. not all at the same time just one at a time to see if it was the magic bullet. None of these did a darn thing. Also changed distributor cap, rotor wires and plugs. I know its getting spark since when I pull a plug cap off to isolate the dead cylinder its gitting a nice strong blue spark. I stethoscoped the injectors and they are all clicking and I put a fuel pressure tester on and am getting 50 psi. Any Ideas? I really like this truck but I swear Im about to go buy a Ford :-(

 

Disconnect the front O2 sensor, see if it runs any better. If it does, replace it.

Welcome to DF!

 

codes might give a clue, got any?

 

Mileage on the engine and possible some compression #'s would help. How do you know it's misfiring on 1,2 and 3? Checking codes? You should reset the pcm and clear the codes/memory after putting in new parts.