Weird engine noise
 

Hi, all. Longtime lurker, first time poster. I tried getting some answers on SaturnFans, but haven't received any responses.

I've been trying to figure out what this strange clattering noise is near the #4 cylinder...You can hear it when revving the engine from idle, and especially when driving under a load/shifting.

Funny thing is, it doesn't happen in open-loop mode, only closed-loop. It's not the tensioner, doesn't seem to be coming from the rockers or EGR....It's more pronounced near the side of the block, a little below where it meets the head.

No misfire counts....No knock sensor counts, either. There's also random sputtering from the exhaust (see the 28-29 second mark in the video to hear it best--I held the phone too close to the tailpipe for the rest of the video.)

New plugs (NGK), new ECT, Cleaned IAC and EGR...did a "steam clean" as well.
Scan software says the IAC "failed test" on all available PIDs....Would a faulty IAC cause this? When I pull the IAC connector, the engine revs to about 3k. So I know it's at least responding to the ECM on some level...

The idle is a little rough and shakes the car, but the top mount is shot anyway.

Any ideas?

2000 SL, 1.9 SOHC, manual trans and 165k

Check your computer codes and post them here. If you don't know how, just take it to your local Autozone, Advance or O'Reilly's and ask them to do it for you.

It's not throwing any codes.

Man, that sure sounds like either a collapsed lifter or an exhaust manifold leak to me. Of course, as everyone here knows by now, I'm NOT a mechanic.

Well, that's the weird thing about it.... Runs perfect and smooth when started...No odd noises or anything until it warms up and goes into closed loop. I'm wondering if the injector on number 4 is halfway clogged...I read somewhere that when in open loop, the fuel mixture/spray pattern is richer than what it is when warmed up.. Maybe it's getting so lean in the cylinder that it's causing some spark knock..I suppose I'll have to pull the plugs and compare them to find out....I'm way past due for a fuel filter change too.

If you can't determine the cause of the noise, I would try a little Seafoam "magic". It works well on my 5.7 L chevy with TBI.

Kinda hard to tell what the noise is from my desk. So I'll say it could be any moving part.


SeaFoam sure thing