I know this is the Intrepid forum, but I like this site and my 300M is similar enough to the Intrepid that I hope you'll forgive me for my question about my 3.5 motor:

Our son was driving our 2002 300m today, when he started to hear a "banging" sound and the check engine light started flashing. He drove it home (ya, I know) and parked it. I was able to pull a P0300 code (multiple misfire). I started the car for about 30 seconds and heard a horrendous banging sound coming from left cylinder bank. What was particularly interesting was that the sound seemed to occur intermittently - like something was going on every second or third firing sequence in one of the cylinders. The sound was similar to sharply rapping a hammer on metal, since it had a slight ringing tone to it. Though I could imagine (hope) that it was a serious case of detonation.

The car has 140k on it and has been well maintained (we're the original owners). I'm pretty much thinking that something in the valve train is shot. However, I'm still holding on to the thought of it being detonation. Any suggestions on how I might diagnose this issue?

Thanks in advance,

Larry

 

Some guys suggested that the rocker assembly was the problem they were correct: One of the rocker arms was broken.


I know I said it sounded like the left bank, but it was actually the right. Judging from the design of the air box-intake-thingy that sits on the top of the engine, it seems like the noise would be heard on the left.

The roller dropped in between the cam and the spark plug tube. On occasion, the cam would come around a strike the roller, pushing it up an out of the way. When the roller dropped back down, it would slap it away again.

Larry

 

Now that the diagnosis is complete, onto the repair:

1) The rocker is obviously toast (see photo #1 below). Do you folks recommend replacing just the rocker, the whole rocker assembly, or both rocker assemblies?

2) One lobe on the camshaft looks a little chewed up (see photo #2 below). However, it doesn't look like the area where the roller rides is damaged. I really don't want to replace the cam. What do folks think about my just cleaning up the damaged lobe?

3) The head doesn't look like it too damaged (see photo #3 below). However the spark plug tube does seem dented, and there is some damage where it goes into the head. I really don't want to mess around with the head. What do folks think about just leaving it as is?

thanks again in advance,

Larry