So here is my issue.....I bought a 2004 Durango 5.7L with a blown motor.....threw a rod. I bought a motor from a guy on Craigslist to put in it. I think it was out of a truck...had a different oil pan and timing chain cover. I also think it was out of a 2006 or newer as it had the MDS system installed. I removed the MDS sensors and filled the holes with the dummy plugs from my bad engine. I talked to a dealer mechanic and a Dodge tech and they both said it would run fine this way (with the MDS camshaft and lifters). They said it would run normal on all 8 cylinders. I switched the timing chain cover and oil pan from my engine to the new one. I put my intake on it and changed all sensors.......knock, crankshaft, etc from the old engine to the new engine. I put the motor in and tried to start it. It started, but ran like crap. It was blowing out white/grey smoke and would not idle. Over 2000 rpm's it seemed like it was running fine, but under 2000 it was idling rough. I kept it running long enough to get a code P0174. I did some research and found that this is Bank 2 Lean, and that typical problems are dirty MAF sensor or dirty O2 sensor. Since these don't have a MAF sensor I tried the O2. Went to Autozone and got a new O2 sensor (before cat). They only had 1 so I installed it on the passenger side for Bank 2. It started and ran a decent amount better but still won't idle. I do have a brand new battery as I've read on a few other threads that this could be an issue. Also the car had a K&N air filter installed when I bought it......I read that those can make the sensors dirty. When I start the car I have to give it gas to get it started. If it is the first time of the day it will start easily. But if I start it and let it run for a minute and then it dies when I try to idle. When I try to restart it is more difficult to restart. The exhaust does somewhat have somewhat of a fuel odor. After I installed the new O2 sensor I started it a few times and would let it run for a few minutes (between 2000-3000 rpms). Every time I tried to let it idle it would die. I got the P0174 code several times and would clear it. After the last time it died, I restarted and got the P0174 and the P0172 (Bank 1 rich). I've only gotten that one once. From what I've been reading it seems like the P0174 code is causing the engine to say it is lean and causing the computer to send too much fuel. I'm wondering if that happened to just make the P0172 trip once.

So I plan to test the fuel pressure and compression when I can get a chance. The oil does not have any water in it. It does not seem to be losing any coolant out of the radiator. I thought it might be water in the gas because of the white smoke, so I completely emptied the tank and put good gas back in.

Anyone have any suggestions where to go next? I'm wondering if I need to replace both of the pre-cat O2 sensors even though only Bank 1 had been registering a code. Any help is appreciated. Thanks.

I meant Bank 2 on my last sentence. Other than the one time it registered P0172, it has only been registering the P0174 code, Bank 2 Lean.

 

Well to update this if anyone happens to search this topic......I ended up doing a compression test and on the passenger side, the front and rear cylinders were both reading 0 compression. I removed the head to find that on the front cylinder, the valve seat had fallen into the cylinder and beat up the top of the piston and head and scarred up the cylinder wall. On the rear cylinder, the valve seat was coming loose and the valve wouldn't close all the way. So I have now rebuilt the engine and am back on the road. But the lack of compression on 2 of the passenger side cylinders is what ended up causing the codes above.