I've been searching/studying the forums for a few weeks now, but I haven't been able to figure out what's going on here....

97 Ram 1500 5.9

A few weeks ago I went on a 400 mile round trip. When I left the house, I thought it felt & sounded a little weak but figured it was just me. About 100 miles into the trip I started running into some decent hills and the truck could barely make it. I quickly realized that even on level ground I couldn't get it over 75mph and I was only getting 10mpg or so. There is no stutter/vibrations/etc. Loss of power, the "weaker" sound, and bad gas mileage is about all.

I made it to my destination and headed home a couple days later and the issue was still there. About a 100 miles from home I finally got a CEL, code p0306.

So - replaced Plugs, Wires, Cap, Rotor, Coil. Not the cheap stuff, except for the Champion plugs. It ran a bit better, but not good. Checked compression- all good. Also replaced the PCV valve/hose, Crankshaft Position Sensor & MAP sensor. Issue is still there. The injector seems to be working. I've swapped the injector wires between 6 & 8, and unplugged the injector while idling and there was the idling did bog down a bit. So I don't think the injector is the issue. Oh- I also ran some Sea Foam through the manifold... wishful thinking.

About a year ago I replaced the following -
Hughes Plenum Kit
Magnaflow Cat
O2 sensors
Throttle Position Sensor

One thing that really bugs me about this is that I seem to have to put 100-200 miles on the truck before the CEL illuminates. But both times, it's been cylinder 6. Is this normal for it to take so long? Could it be the PCM?

Any thoughts/ideas would be greatly appreciated. Sorry for being so long-winded... Just trying not to leave out too many details.

 

Is compression lowest on cylinder 6? Pull the plug on 6? I would say your PCM is working, it's counting a slight or intermittent miss and throwing a cel when it gets to whatever the number is.

 

Is your cat clogging up again?

 

I'm afraid of that... but I sure hope not. What's a good way to figure that out for sure?

 

remove the front O2 sensor from the exhaust completely, go for a drive.

 

That sound brought back memories!

But... it didn't seem to help much, if any. However, I did get a couple of surges of power... just a couple of seconds each. That was the first time that's happened.

 

What were your compression results? Wet and dry test done?? Maybe good time for a leak down test..

 

I don't have the exact results, but they were all around 120-130. I don't really know if I was doing it right... I just spun the engine over for 4-5 seconds on each cylinder. They were all consistent, so I figured that was a good sign.

I'll have to look up a leak down test... I'm not familiar with that one.

One more thing- I just realized that I didn't replace the plugs after running the sea foam through. I just went and popped a few of them out and they aren't in very good shape. I'll make another quick trip to the parts store in the morning to pick some new ones up.

 

I have a similar problem with mine, only i have not driven it enough to get a CEL, but i discovered that i purchased some bad gas. I havent had a chance to top it off with fresh fuel, so i cant say for certain that it will fix it, but its worth a try. Did you fill up just before leaving town? have you filled it up since?

 

I thought the same thing initially but I've ran through a couple tanks now.


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