Okay guys and girls I am new to this forum, but not new to the Dodge Ram. I have a 2000 Ram 2500 5.9l and the other day I was driving down the interstate at 70-75mph when the CHL came on and the truck starting running like crap. I took it down to Autozone the next day to read the codes and it came back Misfire on cylinder 1,6 and 8. There was no other codes just the misfire code. I have replaced the Plugs, Wires, Cap and Rotor early this summer. I have already pulled the Cap off and it still looks good. I haven't pulled the plug out yet, but I know all the Injectors are shooting gas (not sure how good, but they are). I have also reset the computer to make sure it wasn't just a glitch and the CHL came back on again.

What would cause 3 cylinders to misfire at the same time?

 

I forgot to add that shortly before this I had a wierd idle problem where sometimes the Idle would jump around on its own. I replaced the PCV Valve and it seemed to get better, but most of the time it idles fine, but sometimes it doesn't.

 

Your plug wires are not routed properly. There is a TSB out there with the proper routing of the plug wires. Search the 2nd Gen forum and you'll see references to it.

 

The wires are routed correctly, I isntalled them early this sumnmer and the Truck has ran good up until a couple of days ago.

 

OK, if you are positive about the plug wire routing then I would have the cat presure tested at a local muffler shop. There's a good chance they'll test it for free. If the cat is plugged, get it replaced and replace both O2 sensors while you're at it. O2 sensors should be replaced ~ every 65K miles. If they go bad or are not functioning properly, then the engine O2 levels will not be properly regulated which leads to the cat getting plugged.

 

Help me understand this, how would 3 cylinders misfire because of a clogged cat?

 

The cat getting clogged will create excess heat wich can crack the heads and cause misfires but, that is usually cylinder 8.

 

Okay so it is safe to say that it is not the cat since it is 3 cylinders and both sides of the block, and I know I have good flow coming out of the exhaust. What else could possibly cause 3 cylinders to misfire at once? I am going to pull the plugs and do a compression check this weekend to make sure I still have compression, but I am leaning on some sort of sensor failing.ectors going bad at once or 3 plugs going bad once is pretty slim to none. It just has to be a sensor or something like that.

 

I think it would be safe to assume it's not the cat but, I would still check the cat just because VWandDodge knows his stuff. Just get a temp gun and check the temp at the front and back of the cat. If the front is hotter then it's plugged if the back is hotter it's not plugged. As far as a sensor being bad I would think that would be unlikely because it would throw a code. I would think it is something in your ignition system.

 

I will get the Cat checked, but I still don't think it is the problem. I could understand if it was just one cylinder but not 3 cylinders on both sides of the block. Any other ideas that would cause this?