engine runs rough,shakes really bad at certain rpms on 1996 Dodge Ram 1500

my engine was switched out because bearing parts were found in my oil pan during routine change.another engine w/ same miles(95000)was installed.Initially truck ran beautiful. At around 1000 miles, engine SUDDENLY started running very rough and engine light came on.Mechanic checked it out and said p0300 code came up.could this cost more than truck is worth or could it maybe be something simple or maybe put back together wrong?

by in Meredith, NH on December 04, 2010
1 answer 2 comments
ANSWER by on December 04, 2010
P0300 is a random misfire code. Look at spark plugs, ignition wires, etc. This is basic stuff and with a used engine swap, i'm not sure what carried over and what got changed. Tune up items are fairly easy to deal with, so hopefully it will be an easy fix.
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COMMENT by on December 05, 2010
I've now tried plugs and wires. Do you think it's worth it to find someone with a better computer to diagnose or would I just waste my money, which is scarce right now.
COMMENT by on December 05, 2010
You could swap injectors... you have a lot of unknowns here. You could have a wiring issue or even a software issue. P0300 doesn't tell you much - you may want to wait until you get more codes.