cstich08

For starters, my car is an 05 gt with about 85k miles on it with only a CAI and brenspeed SCT tune on the engine.
Yesterday I was driving across campus, low rpm casual city driving and all of a sudden there was a horrible noise from the engine bay, almost sounded like I'd run over something that crunched. I can't really describe it any better because it was obviously unexpected. Following the noise the RPMs fell to around 300 and the engine sounded like it was running on one cylinder with very intermittent ignition and a "glug" sound between cylinder fires. It kept running that way until I turned it off about 20 second later. There were no leaks coming from anywhere and no visible damage. When I tried to restart it, it turned over but didn't come even close to starting. After that I tried reflashing the ecu to stock because my car has had issues starting on the new tune before. When I turned it over again it still didn't start. I decided to try once more which is when I heard a metallic thud that resonates through the engine. I left it alone after that.

As a note I've been hearing a clicking sound coming from the bay for a little while now that changes frequency with RPM and I thought it had been getting worse but dismissed it as me just being a hypochondriac. I gues it did get worse.

Sorry for such a long post but any help figuring out what's going on would be greatly appreciated.

JCON

What oil do you use? Last change? Ambient air temp? Did Air temp affect loudness of clicking? Ever have a water pump leak or failure? Any other major systems repaired or replaced? Did said clicking or horrendous noise start after a hard downshift? Still no sign of any leaking or smoke from exhaust? Any other unusual things going on lately?

Open your oil cap, see any metallic shavings or pieces in there?

Take air intake off and look in manifold any in there?

Can you take the valve covers off? Check for damage there.

JRC702

A metallic noise when cranking the engine is definitely a bad indication.
I would start with a compression and leakdown test.

cstich08

I use royal purple last changed less than 2k miles ago. Air temp is around 70. I didn't think to make a connection between temp and the clicking. Never had a water pump failure or leak or issues with the car overheating. It didn't throw any codes. No hard downshift I was very lightly accelerating maybe coasting can't quite remember. Only system I've ever had replaced is the alternator 3 years ago. No smoke ever. And still no leaks. Only thing strange is I thought it may have been down on power lately. nothing else strange.

Didn't see metal shavings on the dipstick. Haven't checked under the oil cap or in the air filter. Maybe I'll try pulling the valve covers off. I had to leave town with a friend this weekend so I'll try to get it done this week

JCON

That is strange that there are no codes and no signs of any engine problems. Test the battery with a multimeter? Should read ~12V when off and ~14V if running (which doesn't seem to be happening)

cstich08

It hasn't been having any issues with weak starts and the failure to start doesnt sound like a dead battery. And a dead battery doesn't seem to explain the rest of the strange behavior. I took a video of it trying to start ill try to post it if I can figure out how to do it from my phone

JCON

I've not seen anyone with a problem but I wonder if your timing chain was clicking on the cover and broke...

moosestang

Have you tried turning the motor by hand?

DTMR

you're the second guy i know who seized their engine with royal purple oil, I don't trust that stuff

cstich08

With what you've heard what do you expect the damage to be? And how realistic is it to fix? Obviously everything is speculative