I know it is beyond hard to diagnose a mechanical problem via typing words on the internet, but I'm willing to ask anyway. There is a distinct noise going from under the hood when I'm driving (although not all the time). It tend to hear it more so when I hit the gas, although I could still hear it when idle or stopped (but much lower). I can only describe the noise as a clicking type of sound that is intermittent and varying in loudness. I should also say that I have noticed white smoke emanating from my exhaust after I turn the car off. I also prior to this noise had issues with another noise from directly underneath my driver seat where the cat is; I think it is my heat shields rattling though (not sure if any of that is related or not). I should also say that I am due for an oil change, and I have had mechanics tell me in the past that I was low on oil during a routine oil change (4k), and that I supposedly had a tiny leak that would need to be monitored. FYI, I have 187k on my car. I've been the sole owner since 2004. I'm thinking about moving on though since the excessive mileage is inevitably going to be a money pit. Any advice would be greatly appreciated. Otherwise, I have to take it to Nissan and pay $112 for them to try and tell me what's wrong. Thanks!

 

After just purchasing my Z, but being in the mechanic field for the last 12 years (dads a mechanic and I've been in a shop since I was 9) Almost every Z I've seen come in has had one small oil leak or another. And most of the time it's due to a valve cover gasket that did not get RTV'd in the right place or the variable valve timing solenoid gasket had gone bad and leaked down to the front of the engine. There's also been oil drain plug's that are leaking because of gaskets (which should be replaced every oil change), or oil pressure sensors/oil filters that are leaking out of gaskets and mating surfaces. Also high mileage Z engines do tend to consume a little bit of oil depending on how hard they've been run. Depending on your definition of a little bit, is your oil 1/4 quart low? or like 2 quarts low? As for the ticking noise, might be time to pull valve covers to check the valves and lifters. Possibly something simple, or maybe something not so simple. If the tick speeds up when you hit the gas and slows down when you let off I would bet it's valve train somewhere if it's coming from under the hood. As for the noise under your seat.......Have you checked underneath it for loose parts? felt for play in the driveshaft? shake the exhaust around and see if you can re-produce the rattle at a stand still with the car off? If you have 187K and the car is still working pretty well without any MAJOR issues in the past then it's probably a car well worth putting a little money into since it's been so good to you. Checking the ticking with the old screwdriver to ear method never hurts either. Isolate where it's coming from and let us know! Wish you were closer to me, I'd be happy to come help out

 

This is the problem with "typing words on the Internet" and asking for help in diagnosing automotive problems. Problem #1 is that you're describing several problems and all will have their own distinctive solutions. #2 is the sound you're describing as "intermittent" and "clicking" is not nearly descriptive enough. Where does it seem to be coming from? Does it appear at a particular RPM? Is it loud enough to make you think something is being damaged?

Kjfire4life has some good suggestions, but it sounds like he has some wrenching experience and you do not. Have you tried jacking up the car, supporting it on jack stands and taking a closer look at it yourself? As for the 187K mileage, that shouldn't be any obstacle for refreshing a well-cared for Z. Most people LOSE money when they let their own fears dictate when they buy/sell/trade-in cars.