2001 RAM Sport 5.9L.

About 9 weeks ago, I put in a new CKS, CPS, distributor cap, rotor, plugs and cables.

As of Tuesday morning (last week), the truck was running fine.

That afternoon, I ran an errand and pushed it pretty hard (lots of sharp curves and hills) and it ran fine.

That evening, was going up a hill and it shuddered really hard three times - like WHAM, WHAM, WHAM.

No more trouble that day, buy shook really bad going up a hill the next day. By Friday, it would barely make it up a hill and top speed was about 45. Any faster and and the engine would start shaking really bad.

Friday evening, the CEL came on with codes 300, 304, and 306. (Misfires on cylinders 4 and 6.)

I pulled the forward O2 sensor to verify that it is not a clogged cat.

Fuel pressure is good.

The only other clues are:

1. If you try to rev it up a little, you will get the sulphur smell of excess gas hitting the cat.

2. I was never happy with the way the replacement distributor cap (or rotor) fit. It felt like it was too short or the rotor was too tall. That is probably a red herring as it has been running fine with it. I ordered another new one and will swap it out just because.

Ideas?

 

Sorry, but. Pulling the o2 does not mean the cat is not clogged. And if you have a problem with the way the distributor cap was installed, I'd check that out too.

 

Let me phrase it this way: Other than the slight volume increase, the symptoms were not lessened at all by pulling the sensor.

The distributor cap is a long shot. My guess is that if it was going to be an issue, it wouldn't have waited 8 weeks to do it. The new cap and rotor will not be here until Wednesday. I will swap them then and see if anything looks weird inside the cap.

I am also thinking about replacing the the forward O2 sensor and the MAP sensor. I kind of hate to just start throwing parts at it though.

 

Nah, don't just throw parts at it..... waste of money. Have a look at the plugs for 4 and 6, also check your plug wire routing. (TSB for that in faq section.)

 

If the plugs are ok and the wires are properly routed, I'd check the fuel pressure, and the injectors on bad cylinders.

 

I will check out all your ideas.

Something to keep in mind though:

Fuel pressure is good. I tested it with a gauge Friday evening. It did bleed down pretty quick, but that is because the connection from the hose to the gauge leaks pretty bad.

I believe I have the wires routed correctly.

I could definitely support the idea that an injector or two are stuck open (based on the sulphur smell).

My other thought was that either the MAP or the O2 sensor might be causing it to run extremely rich.

 

I forgot to mention: I also replaced the coil when I replaced the plug, wires, cap, and rotor.

 

If the O2 is bad, meaning it's giving wacky readings, the PCM will more or less just ignore it and run a preset amount of gas all the time so it doesn't do stuff like you're getting.

I'm betting injector.

 

I pulled plug #4 (one of the misfiring cylinders). Photo attached. It smelled like fresh gas. I also pulled plug #1 for comparison. It smelled like exhaust.

What are the odds of two injectors going bad at the same time?

This truck has been running great, 500 miles a week for 8 weeks.

 

I'd check and make sure cylinder 4 and 6 plugs are firing. If not, go from there. Might be a problem with some of the replacement ignition parts (cap, wires, or plugs). Check to make sure wires are still seated properly, etc. Maybe clear the misfire codes, swap a couple of plug wires, and see if the misfire codes move.