Good morning all! I have a 2003 ram 1500 4x4 quad cab with the hemi. It has just over 105,000 miles. About a week ago going to work it ran fine as usual. When I was about 50 feet from my parking spot it just started running like it had some bad gas, then stalled. I was coasting, not even going 5mph when this happened. It had just over 1/4 tank. I put 2 bottles of dry gas in it and 6 gallons of premium gas in it and it still won't start. It will only start if you pump it and you have to keep working the pedal to keep it running. It threw a generic code P0300, random misfire. I changed the cam sensor, crank sensor, pcv valve. We checked the coil packs for a short and they are fine. The fuel pressure is good also. There's no water in the oil. If there is an EGR valve, it's well hidden. I am going to change the upstream O2 sensor. But I think it's the computer. I highly doubt that it's a broken valve spring. That wouldn't take the whole motor out and make it run like it is. Any suggestions? Thanks

 

Random misfire means two or more cylinders are not firing right so i would start with the cheapest thing that had to do with the firing and thats spark plugs, Champion Coppers are what Dodge Put in and also what the truck likes best(read any thread on spark plugs Champion Coppers rule overall with hardly any problems). And they say they only last 30,000 miles so looks like your over due

 

Thanks, but I just changed them last summer with champion coppers. I changed them at 90,000. And it was running fine then.

 

Sorry you didnt say you changed them.
Upstream o2 is a good start make sure to only use The original MFG for the o2, i think its NTK thats who made mine, I say this becuase the other brands tend to not work.
ROCKAUTO.COM has o2 sensors at half the price of parts stores.

And no you dont have EGR isnt it nice!!!!! I dont care enough about emissions to ruin my truck by putting something in it that dosent burn!

 

Sorry, I forgot to mention that I changed them. It only took 3 hrs. Thanks for the info on the O2 sensor.

 

Yeah i figured it would help on saving some money

 

Well, I changed the o2 sensor the other day. Still no good. I guess the computer is next.

 

That's a big leap of troubleshooting..... I would do a compression and Leak down Test before I replaced the computer, you might just have a headgasket/piston ring problem causing a loss of compression thus causing a misfire condition.

That would be my next step before spending big $ on a new PCM....

 

Yeah no kidding... 50 bucks for a compression test or 500 for a new computer,
btw im changing the haed gaskets now on my 03 hemi and because of the head gasket leak i had a o2 sensor code, lean condition code, random misfire code and a #4 cylinder misfire all at different times before i changed the gasket so think about the little things before you spend big bucks that end up not fixing your problem.

 

It just seems like the way it's running, that it would be the computer. If 1 cylinder is out, I don't think it would make it run like it is. It's running like it's running on bad gas. But, I forgot to mention that when I was checking stuff before, a message popped up on my dash. It said "buss error". This came up after I first connected the code reader up at the beginning, because the engine light came on. The code reader picked up a generic code, P0300. When I looked it up on the internet it had a list. A code P0300 may mean that one or more of the following has happened:

Faulty spark plugs or wires
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector(s)
Burned exhaust valve
Faulty catalytic converter(s)
Stuck/blocked EGR valve / passages
Faulty camshaft position sensor
Defective computer

I've changed the plugs, cam sensor, crank sensor, upstream o2 sensor. There isn't any EGR valve. The funny thing is, it was running fine. When it died, I was coasting maybe 5mph in the parking lot at work about 50 feet from my parking spot. It just started spittin & chuggin & that was it.
The only thing left to check is the catalytic converter & the computer. I checked everything else. Does a repair garage have the equipment to check the computer? Or is that a dealer thing to do?