Engine knock/slap/tick?? I've check almost everything...

[99gst_racer]

The engine is a stock 7-bolt.
In the middle of a spirited drive last week, my car jolted and bucked similar to hitting fuel cut. Then a large puff of black smoke rolled out of the tailpipe.

The car still starts and drives, but I am know experiencing a knocking sound. I'll try my best to describe the sound. It's a third of the loudness of rod knock, but 3 times louder than lifter tick. Sounds like lifter tick on roids. The noise is very consistent and RPM dependent, and it amplifies with RPM.

I immediately pulled the valve cover, but nothing was out of order. Cam caps are tight, lobes look great, lash adjusters and rocker arms are in place, and oil is circulating throughout the head like normal. I also have good oil pressure. We turned the engine over by hand, and verified timing. The marks line up correctly, and tension is still correct.

The engine does not leak, burn, or push any fluids at all. We drained the oil , expecting to see metal shavings, but we were wrong. The oil was still clean and free of any foreign material.

I did a compression test a few days prior, and I got 175-170-170-165. I'm going to do another compression test in a couple hours on my lunch break, so I'll report back with that.

A few days prior, the car was throwing a code for "cylinder #3 misfire", and I never did trace the problem. I could clear the code, shut off the car, and restart, and she ran like a champ - no more misfire.

One more notable detail - when turning the crank manually, it seemed to hit a "hard spot" that required much more energy to turn past.


What else should I do or look for? We're probably going to pull the head soon if I can't figure this out. Anybody else got any advice or tips? I'm thinking there could be a problem with a valve, but I can't understand how it could have happened.

 

[95GSXBLUR]

Wait on Pulling the head - If I were you, I'd pull the PAN first.

When my 7 bolt walked, and spun 3 main bearings, I had a loud Knocking noise. Was very consistent @ idle, like BAM BAM BAM BAM and would increase with engine speed. The car ran and drove, with out burning or losing fluids.

I hope that's not your problem, but before you waste a head gasket, Pull the pan. Permatex is a lot cheaper than a head gasket.

There wasn't any metal in my oil either, but when I opened the pan up, there was a lot of copper.

Make sure you check your crank pulley for separation as well. Sometimes those make weird loud noises when they're about to fling apart.

That's all I can think of - I hope that helped. Check your crank pulley first, Obviously... then I strongly suggest you pull the pan.

 

[Strm Trpr]

Yeah Paul, hold off on pulling the head.
I'd pull the pan first.
I'm sure you've done a BSE already, so it couldn't be a balance shaft bearing.
Unfortunately, it sounds like perhaps a you had another misfire, possibly
loaded the cylinder with fuel, and then it exploded when the cylinder fired
again possibly bending a rod, or damaging the rod bearing.

Good luck and let us know.

 

[toybreaker]

Man, that's a bummer!!!

Knocks/noises are really hard to diagnose long distance, but there's a few things you can check to narrow things down. I hate tearing a motor down to diagnose an engine noise. I certainly wouldn't drive on it, but running the engine a bit in the shop might enable you to determine which cylinder, or what area of the engine is the problem.

How does it respond to temperature? On a cold start the oil is thicker, and will ~somewhat~ cushion a rod knock. After a few minutes run time, the oil will begin to thin enough to run away from a rod with clearance issues, and the noise will become more pronounced.

If you hold the motor at ~1500rpm, and then give it some revs, can you hear it get worse, (on accell) and then fade, (on decell) and then come back again at idle?

Your comment about a "tight" spot is very interesting! Can you pull the plugs, (to eliminate compression as a factor), and then roll the motor around by hand to find the tight spot consistently? I would look at the crank dampner, and maybe mark it at the tight spot and roll the motor over by hand again. If it's getting tight at the same spot, and it happens to be tdc, one (or both) of the pistons at tdc may be kissing a slightly bent valve, or the head.

Can you disable the injector at each cylinder and find one that makes it quiet down? If removing the combustion event doesn't change/eliminate the noise, it starts to get harder to pin down the source.

It's an interesting anomoly that a couple of the 2g motors brought into my friends shop for a "rod knock" have shown evidence of the pistons kissing the head. During machine work, if the block is decked substantially, the piston height starts to get a little close to the head at tdc. All it takes is a rod big end loosening up some to give you a funky rapping noise. If the knock seems too high in the motor to be a "real" rod knock, this may be your issue. The combination of a short block deck height, a forged piston with it's slightly larger side clearance, and a rod clearance beginning to open up lets things get a little too close for comfort when the piston "rocks" at tdc. This will really be noticable on the exhaust stroke, as there's no compression load on the piston. This noise will not change appreciabbly with that cylinders injector or spark disabled.

Checking the drain oil for particulates is always a good thing, but the oil filter will catch most, if not all, of the beginnings of a bearing failure. This lack of metal in the drain pan can be somewhat confusing at first. Even though the pan may be clean of metal, I've found that the oil in an engine with bearing distress will have a "coppery" tint to it. It may be hard to see, but if you stir your drain oil in the pan with a screwdriver, whilst shining a strong light on it, you'll see a coppery shimmer to the oil.

You can also cut the filter open, and that will tell the tale. If it's full of silver and copper, that's a bad sign that things will have to come apart.

Good luck, and please let us know what you find!

 

[99gst_racer]

Pulled the pan last week - it wasn't pretty. My overboosting rampage left the #1 and #4 rods bent.

#4 Rod

I pulled the engine and tranny yesterday. The build begins.
Thanks for the posts, gentlemen.

 

[GSTeclipse]

yep been there done that ....thats about the point where they give up

Good luck and have fun !