Brad Yates
Junior Member
Ok, so I have a 2005 Ram 1500 with the 4.7 liter engine. The engine was replaced before I bought it (somewhere around 50,000 miles the previous owner ran the engine dry, he claimed an oil change place left the plug out.) The engine was replaced with a reman so I have no idea how many miles are on the engine. The truck has 130,000 miles on it.
A while back I was getting an intermittent misfire on the 8th cylinder, I was also getting some water in the oil, not a lot but it had progressed from me thinking that maybe it was just some condensation to realizing I definitely had a head gasket leak. Finally, the engine had an audible timing chain slap, so I decided to rebuild the engine.
Upon tearing down the engine I found that the intake valve on the 8th cylinder wasn't sealing very well. I lapped all the valves until I got a good seal on all of them. I also replaced all seals and gaskets, timing chain and tensioners, lifters, crankshaft and rod bearings, piston rings, water pump, fan clutch, pcv valve, and spark plugs. I checked all my tolerances and they were within spec. It already had .5 over pistons installed so I just did a light hone on the cylinder bores.
Once I got the engine all back together it ran fine for a week or two and then it developed a random misfire. At first I couldn't really tell when the misfire was coming I just got the P0300 code. I checked compression, fuel pressure and spark plugs all are good. I checked for vacuum leak, it doesn't have one. I had the battery checked and its good. The misfire has gotten progressively worse until it is now very noticeable. Interestingly enough the misfire comes every time I start the truck. Not immediately upon ignition, but as soon as the engine gets a little load on it, like after I back out of the driveway once I get about half way down the block. I will let off the gas and the engine will level out and the misfire will go away. At this point I can drive around town, get on the interstate, let the truck idle, whatever I want and the engine will run smooth with no misfires. But as soon as I turn the engine off and let it get even a little below operating temp the misfire will return upon restarting the engine.
In the freeze frame, bank one is always normal and bank two is running rich, with the short term fuel trims anywhere from -25% to -35% on bank two. In desperation I have replaced the EGR valve and IAC valve, neither of these have had any effect.
I am out of things to check and parts to throw at it. Has anyone experienced this problem before or have a suggestion of something else to check? Any help would be greatly appreciated.
A while back I was getting an intermittent misfire on the 8th cylinder, I was also getting some water in the oil, not a lot but it had progressed from me thinking that maybe it was just some condensation to realizing I definitely had a head gasket leak. Finally, the engine had an audible timing chain slap, so I decided to rebuild the engine.
Upon tearing down the engine I found that the intake valve on the 8th cylinder wasn't sealing very well. I lapped all the valves until I got a good seal on all of them. I also replaced all seals and gaskets, timing chain and tensioners, lifters, crankshaft and rod bearings, piston rings, water pump, fan clutch, pcv valve, and spark plugs. I checked all my tolerances and they were within spec. It already had .5 over pistons installed so I just did a light hone on the cylinder bores.
Once I got the engine all back together it ran fine for a week or two and then it developed a random misfire. At first I couldn't really tell when the misfire was coming I just got the P0300 code. I checked compression, fuel pressure and spark plugs all are good. I checked for vacuum leak, it doesn't have one. I had the battery checked and its good. The misfire has gotten progressively worse until it is now very noticeable. Interestingly enough the misfire comes every time I start the truck. Not immediately upon ignition, but as soon as the engine gets a little load on it, like after I back out of the driveway once I get about half way down the block. I will let off the gas and the engine will level out and the misfire will go away. At this point I can drive around town, get on the interstate, let the truck idle, whatever I want and the engine will run smooth with no misfires. But as soon as I turn the engine off and let it get even a little below operating temp the misfire will return upon restarting the engine.
In the freeze frame, bank one is always normal and bank two is running rich, with the short term fuel trims anywhere from -25% to -35% on bank two. In desperation I have replaced the EGR valve and IAC valve, neither of these have had any effect.
I am out of things to check and parts to throw at it. Has anyone experienced this problem before or have a suggestion of something else to check? Any help would be greatly appreciated.
