Spun rod bearing??
 

Last night I was driving my 1999 Miata and I noticed it started making a loud chatter/knocking sound between 2,000 and 3,500 rpm on accel and decel. I stopped at a red light and the car died. When I tried to crank, it was cranking very slowly, like it was struggling to spin. Now when the car starts, it knocks, stops until 2,000, and starts again. Is this a spun rod bearing or something else?

Sounds like something very wrong in the motor. Pull the valve cover off to make sure it is not something catastrophic in the valvetrain first. If it looks normal, I would think it is in the bottom end like a rod or main bearing.

Please do not start the motor again. If it is making loud noises, you need to shut it down as soon as possible. Continuing to run a motor that is knocking will eventually cost you a whole lot more money to fix. If something comes apart, you will end up losing your block and or cylinder head as well.

Before you pull motor do this

look at harmonic balancer

look at alternator bolt

test battery voltage

look at your pulleys and shit on front of motor

I know it sounds stupid, but do you have oil in it? Sounds to me like it ran dry, spun a bearing and is knocking. It's having a hard time cranking because of the terrible amount of friction on the crank. It sounds like you are perfectly describing what my car did when it ran w/o oil. Look at it as a way to upgrade the bottom end.

Oil level looked good on the dipstick. But I haven't drained it yet. I haven't really bothered since I've got a fully built 1.8 motor built by Gas Head Motorwerks on the way lol.

By the way, what's the selling policy on here? I know on some forums you need to be a member. I have some Eagle forged h-beam rods I need to sell. Brand new.

Spun rod bearing with be easily evident throughout the ENTIRE rev range. From idle to red line. When mine went, it sounded like a card in the spokes of sorts. Could easily be heard at idle all the way to red line, no difference in volume, only speed of click obviously.

What the fuck, I meant to reply to the other thread.