I have a 1998 2.5 4 cyl dakota with about 90,000 miles. The engine developer a knock about a week ago. It is a loud metal on metal knock that happens all the time the engine is running and is lougest at idle and low rpm. It quites down at higher rpms. My son drove it 30 miles in city traffic after the knock started. From the best I can tell (using a hose as a stethoscope) the noise appear to be coming from right behind the camshaft pulley. I removed the spark plug wires, one at a time, at idle and the noise did not change. The knocking noise is in sync with the spark (ie. half that of the crankshaft rpm).
I have removed the timing chain cover, then valve cover and finally the head and there is no sign of the cause. When I rotate engine by hand everything seems to be moving smoothly and normal. The next step is to pull the engine but before I do, I wanted to check to see if anyone else has seen this problem or has any ideas.

 

sounds like a cam bearing, or maybe even a crank bearing
i've not had to replace mine but you can do it with the motor still in the truck

 

ok, if you pull the timing chain, try to wiggle either the crank or the cam.
and a soild rod works better than a hose for listening, like a wood dowel

 

No noticable play in either crank or cam. I finished removing all the accessories. Hope to borrow an engine host tomorrow. I am going to try leaving the transmittion in when I pull the engine. Its been 30 years since I pulled an engine. Hope I remember how to do it

One major plus with this 4 cylinder... there is plenty of room to work on it. I could use my impact wrench to remove the crank pulley without having to pull the radiator!

 

you might have a bad wrist pin in the no.1 cyl. or a bad rod bearing. my jeep was doing the same thing and it was the rod bearing (the 2.5l is the same motor as a jeep 4.0l just cut down two cylinders). theres really no way of exactlly telling you what your problem except for tearing it down and finding the problem. im sure you got a bad bearing in that motor though.

 

pulling this motor is probably gonna be one of the easiest,

 

i would say that its the only plus...

j/k

 

Finally got around to pulling the engine. It ended up being a broken piston skirt on #2 cylinder. The good news is that it did not score the cylinder wall, so it was an easy rebuild. It needed to be rebuilt anyway. The bearings were worn however the crank was still in good shape and only needed to be polished. New bearings, piston and rings, and it should be good for another 100,000 miles

 

NICE, another dakota on back on the road.