Loud knocking sound started suddenly. It seems to be coming from top/front of the engine. The engine ran fine, started easy, no missfire, idled, accelerates. Knocking speeds up according to RPM's. I ran the motor for about 30 seconds with the valve cover off. Plenty of oil squirted everywhere, the motor still knocked. I ran the motor for a few seconds without the front cover and serpintine belt, still knocked, just louder. Made a pretty good oily mess.

I thought it must be the timing chain so I changed the entire kit. I found the old tensioner was all the way extended, and the chain had a little slack. I thought that was the problem. Sadly not, the knocking persists. The new chain ect. looks good, the motor still runs fine, starts easy, idles smooth, accelerates normally, no missfire. I'm satisfied with that. I ran the motor for about 15 seconds afterward without the serpentine belt, it's not anything belt driven. I can't find anything that appears to be a place inside the front cover or the valve cover where they are being struck by anything. Right now I'm ready to assemble everything that runs off of the serpentine belt.

When I first took off the front cover, there wasn't a top chain guide. I've seen them in some of the videos, that might be important.

I think it's something simple. I'm convinced the motor starts and runs too well to be anything major. It just knocks loudly. I think I could drive the car down the road, but I haven't since the knocking sound started. Since electronics, sensors, and diagnostic machines I don't consider myself much of a mechanic anymore. In any case I'm out of practice. But I think with a little help I can figure this out. Your help is appreciated.

I need to get this car on the road, it's in excellent condition.

 

Kill one cylinder at a time and see if you can change the noise. If you can, pull it out and take it apart. It is still a mechanical engine like you worked on before.

 

That sounds like a good idea.

Let me tell you what I've already done.

My first thought was it's thrown a rod. Before anything else I took the spark plugs out one at a time and stuck one end of a soda straw down on top of each piston. Then I turned the motor over by hand and watched the straw go up and down in every cylinder. Plus the motor doesn't miss, so I don't think it's thrown a rod.

 

What was oil level prior to disassembly?

 

Full of oil, still is. Hasn't overheated. I drained the oil yesterday and there were no particles. Put it back in.

 

You can't check for a bad rod bearing by piston movement. You need to drop the oil pan and plasti gauge the rod and main bearings. Sounds more like a rod bearing to me than anything else. Of course, I'm not a mechanic. I've just worked on my own and various friends cars for about 50 years now.

 

Started the car this morning. Easy start, choke function, idled smooth, accelerated normally. I removed and replaced one spark plug wire at a time. Other than creating a misfire every time, no change. Knocking sound continued.

 

Back in the 80s GM 4 cylinders in the x body cars carbon knocked like crazy. A piece of carbon broke free and got taught between the piston and the quench area of the head. A top engine clean solved the problem, you might consider trying some top engine cleaner. If not just pull it out and tear it down. If it is a nice enough car to justify the effort and you have the skill set. I say that because I am saving a 1960 Rambler Super Six and it is worth it.

 

Do all of your parts homework before you tear it down. 91 + 92 are unlike 93 to 2002 in many ways. From injector types 2 vacuum EGR s to Pistons two valves to heads.... Us became oil burners within the first 50,000 miles.

Just saying