Engine Knock

[syrupninja]

I was driving to work this morning, and just as I pulled into the parking lot, the slight tapping, which I attributed to nosiy valves turned into a serious knock. A metal on metal knock. Absolutely the most horrid sound any car I've ever driven has made. It's been tapping slightly since I bought it, and I've put less than 2k on it. It's a 92 with 120k on the odo.

The only recent changes I've made were changing my oil from 20W-50 to 10W-30, and removing the lower upper timing chain guide. It was running fine until today, so I have no reason to think that I messed up the timing, but possibly I didn't use enough rtv when putting the timing cover back on.

It idles very rough, surging in rpm's and after a minute or two dropping to 500. The whole car shakes while it's running, and the sound damn near breaks my heart.

I find it strange for it to run fine for a week and then just start out of nowhere. It's parked at work right now, as I'm afraid to drive it.

Is it time to scrap the motor or is there a possible solution I'm possibly overlooking?