Hey guys, new to the site and having some problems with my car. I used the search feature and found similar problems but nothing quite the same. Here's a little background on the car:
2004 G35 Coupe, bought it mid February with 134k on it. Everything was in great shape mechanically and the previous owner said the engine was recently rebuilt. He claimed to have lost the receipts, but the aluminum on the block looked brand new, so I'm not sure if it was rebuilt or not. Anyway, the car has been running great since the day I bought it up until today. When I left for work this morning it started and ran fine, but as soon as I pressed in the clutch to stop at a red light off the freeway, the rpms dropped all the way to zero and the car wouldn't start, acting like it had a dead battery. I figured it was a faulty alternator so I had it towed home and replaced the alternator, had the battery checked, and put it on the charger. Still wouldn't start, even with jumper cables. After going through some wiring for the alternator/starter motor we got it to start, but it had a loud ticking noise and a very rough idle, sometimes stalling. And whenever I rev the engine, when the rpms won't stop at idle speed, they just go all the way to zero. I'll attach a video to what it's doing. The car never overheated, has no check engine lights, and is not going into limp mode. The oil was a little low but only about 1/2 quart.
Edit: just re-checked the oil and it was quite a bit lower than I originally thought. The oil pressure light never came on though

 

Anyone? I've got nothing at this point so any input is appreciated

 

sounds like rod knock.sorry

 

Does sound quite a bit like a rod knock, was it low on oil then? I had a similar noise and was also very low on oil, but I changed and filled the oil instantly and it has been gone for quite a few months now.

typically once the oil light comes on you are too late, I'd look into sourcing a rebuild kit or a good shop depending on your mechanic skills

 

swapping an engine is often times cheaper than rebuilding.

You can pick up a 100k and bellow non rev DE for $1200 and bellow. Anything over 100k is $700 and under.
I sold 2 motors all under $500 with 170k, 84k.

 

It was low on oil, but like I said the oil light never came on. I added oil but haven't changed it. Would rod knock cause the rough idle/stalling issue?

 

As far as rebuilding or replacing the engine, I'm a mechanic so I would be doing either myself. I'm leaning towards rebuilding, for a little bit more I can upgrade the internals and essentially have an engine with "0" miles on it. For about $2500 I can get eagle rods, wiseco pistons, acl race bearings, a full timing kit, new water pump,new rev-up oil pump, and a new clutch while I'm in there

 

how low was it? When I changed my oil I was about 2 quarts low and have had the engine inspected and everything was fine, luckily, although I have no idea why it didn't explode. I can't answer whether or not it would cause the rough idle question with 100% certainty. I'd try cleaning your MAF sensor and see where that gets you.

If you're a mechanic then rebuilding the engine is probably the best option. plus as you stated you'll have a virtually new engine, and know it's relative history.

I wish you the best of luck and if you do an engine build start a thread! I'm debating on building my engine this summer as a bit of a project

 

if it's an option it's the best one.

Will get rid of oil consumption for good.

 

If you're a mechanic, why would you just blindly assume it was the alternator and replace it when the car didn't have any symptoms of a weak alternator? You could have just checked the battery voltage when you got home to determine if the alternator had caused it to die and if it was putting out 11.5+ volts, it's safe to say that your alternator was not the problem, or at least tried to start it using a jump or a recharged battery first.

I am not trying to make you feel bad... but I bring it up because you're talking about doing an engine rebuild yourself when you don't even know how to troubleshoot simple problems on a car. Are you sure you really want to spend all this money on expensive parts and maybe risk messing up the install?

That being said, have you tried lifting the front end, and listening from underneath the car to see if you can tell whether or not the tick is coming from the top or bottom of the motor? Could be a failure in the valvetrain.

 

As I said, the car died and when I tried restarting it, it was acting like the battery was completely dead. This lead me to believe that the alternator had failed and thus completely drained the battery as I was driving. I have raised the front end and it's very hard to tell whether it's coming from bottom or top end. I've got a stethoscope I'll be putting on it this weekend. If that doesn't reveal anything I'll be removing the valve covers and oil pan to see if it reveals anything. I've rebuilt engines before and I'm confident I would be able to get everything back together and in spec without any issues

 

Also, just to clarify, i don't work as a mechanic, but I took auto mechanics in high school and college and have been working on cars for nearly 10 years. I was also thinking valve train because the rough idle seems like a vacuum leak, something a bottom end problem wouldn't cause

 

You think that would be the best route to go, then?

 

all depends if the car is a keeper.

if it's something you going to sell a few years later, might as well pick up a used motor with low millage and put that in. It is much simpler of a job and cheaper. It will start consuming oil later on (as all of them do).

you build the engine, you get rid of oil consumption for good. It cost more and more time consuming. You will probably not get that extra money back when selling the car, but it's defiantly an investment if you plan on keeping it for long time.

 

I think the low oil ticking is valves tapping until they get lubed.