My 1996 ram 1500 4x4 has a serious drivability issue that I have been unable to nail down. I have a misfire on 1, 4, 6, 8 but have fuel and spark an the compression appears to be fine. The tester I used wasn't exactly up to snuff, but it read the same for the known good cylinders. It was converted to a standard a few years ago, well done job and ran great until someone climbed in somewhere and did something that I haven't been able to figure out. I replaced the automatic brain with the proper 5spd brain so that it wasn't looking for sensors that no longer existed and that did nothing to help the operation of the motor. Problem occurs any time the engine is running, idle to 3500rpm and up doesn't change.

Any help is greatly appreciated as this is the only vehicle I have to drive and its not doing itself or me any good in current status.

 

How's your plenum? Has that been fixed yet? Has it had this problem since you have had it? Or is it something that just cropped up recently? Do you know if they changed the crank position sensor when the did the auto/manual conversion? Hows the cat? How old are your O2 sensors?

Might try removing the front O2 sensor from the exhaust, and take it for a drive, see if your miss goes away.

 

I don't honestly know much about it. I have only had for a few weeks and it has done this since before I got it. the computer never registered any DTCs for anything. the downstream o2 sensor is smashed and missing. The problem started a few months ago but I haven't been able to get any more information on it. I don't know anything about the plenum or where to locate or how to change it but I have noticed some oil in the air cleaner box. Can I have some information on the plenum if you have a good source?

 

Check the be-all, end-all, plenum sticky at the top of this forum. More information than you really want.

Rear O2 really shouldn't have much to do with it, but, it SHOULD set a code......

Might try pulling out the crank sensor, and see what it looks like. I don't recall if the manual version was longer, or shorter, than the auto version though. (Though the information is here on the site, in some of the conversion threads we have...) Either way though, if it is the wrong one, it will cause issues.

 

Thank you for the help. That's more direction than what I started out with. I will post the results here when I find something.

 

Just curious how you determined this? Are you getting codes? Did you try to reset the pcm?

Exactly what happens? Does it stall, Run rough?

Take the air cleaner off and open the throttle blades then look down it and see if you see any oil at the bottom. If you do then you need the plenum fixed.

 

Runs very rough, replaced the pcm with the 5spd. Found no codes on either the auto or 5spd pcm. I unplugged the spark plug wires while it was idling and it doesn't run any different with those specific wires disconnected.

 

But you are getting spark on the cylinders that are missing??

 

HeyYou: Yes I am getting good spark on those cylinders, and even went through and double checked the firing order to make sure I didn't screw it up when I did the tune-up

 

Actually we had a code for the upstream o2 sensor short to voltage.