where to begin? My 97 ram 2500 5.9l started misfiring and showed a code 11. changed out the cam sensor, crank sensor, complete distributor, cap, rotor & wires. Coil is new as well. checked timming and reset sync and all is with in range. Still missing. still showing code 11. traced all wires looking for shorts or bad grounds with no luck. Any clues out there other then pcm? has 230k on it and timming chain and gears were changed two years ago.

 

Is it random misfire, or limited to specific cylinders? If its just one cylinder, swap the injector on that cylinder for the one right next to it, and see if the miss moves with the injector. If it doesn't, time for a compression test.

Have you done anything with your plenum yet? (see stickied post at top of this forum.)

 

Random misfire. starts fine and idles for about a minuet or so perfectly. then begins to mis. then will idle fine, but at 2k rpm it begins missing. tac jumps around. injectors seem fine and compression is good. have a tech friend that is helping and says its not fuel related.

 

Given the symptoms, I am thinkin' it is indeed fuel related..... just for giggles, unplug the pre-cat O2 sensor, and drive the truck. If the problem goes away, replace the sensor.

I am guessing here that you have a fouled sensor, due to the blown plenum.

 

hey thanks, It's worth a shot. I'll let you know. FYI cat was punched out few years ago. don't know if that matters or not for your suggestion but i will try anything at this point. Need to get the old girl on the road.

 

Clogged cat is another sign of a failed plenum. Might wanna pull the air filter housing off, and have a gander down the throttle bores.... see if you see any oil pooling in there. Does the truck go thru oil at all?

 

or the sign of a cat with 230k on it.... I just resolved my misfire issue and I have no idea what actually fixed it since it went away after putting the original injectors back in and changing the oil which had fuel in it and adding engine restore when changing the oil.... I replaced all tuneup parts as well as a cracked header and still had the misfire up until putting the original injectors back in.... I guess its possible some of the white smoke I was getting with the original injectors was from a leaking head gasket and the stop leak just started to work coincidentally when I put the original ones back in? in any case I'm not complaining its running great at the moment...

 

double post

 

Okay, plenum is fine. started tracing 5 volt system to look for short. unplugged map sensor and the engine ran fine. replaced map sensor and kept missing. definitly an electrical problem. unplugged 02 senors with no change. checked wires for damage at map sensor. no such luck. it's in 5 volt system somewhere. any suggestions or folks out there who have experienced similar problems?

 

OK. If MAP Sensor (do these have MAP?) is unplugged and no misfire, then when connected again, misfires, then I would suspect MAP sensor. But I am sure that on 99, it is MAF sensor.

At any rate, that would be suspect and not necessarily electrical problem.