So couple months back I got a 2003 350z. It's extremely nice and sounds nice but the engine is all stock. It's also a automatic.(ya I know) we'll I know people say autos are slower but my Z is running extremely slower then others. It tops out at like 116 an takes ages to get to that mph. I've jokingly raced many friends in 4cylinder cars and slow trucks and still manage to lose or accelerate the same. Everything looks and sounds right I have no idea what happend. If you could throw some suggestions tha would be great,
Thanks!

 

Has it been a gradual loss of power? Are you getting terrible gas mileage? What cars are you comparing to? There are some 4 bangers and trucks out there that will seriously embarrass a stock Z.

 

tune up
bolt ons
transgo shift kit
3.5 or 3.7 diff
uprev tune

then go beat all your 6mt friends

 

I get like 10-15mpg... And just like Toyota camrys, civics and like just old trucks that trust me are slow. And I don't think it's getting slower at all it's just always been since I got it.

 

Have you taken the car to a mechanic? Any check engine light on issues?
Is the air filter dirty? Are you up to date on maintenance?
Is everything OEM on the car? Things could have been modified and returned to stock in a way that makes the car not perform properly.

 

Something is seriously wrong. 10-15mpg? that's not right, majority of us see 21-22, hell some slow roll it to 25mpg.

Have you replaced the transmission fluid? Diff fluid? replace the two cam sensor and crank sensor? Have a factory reset on the ecu and see where that goes.

 

Your MPG alone proves something is wrong. I drive with a lead foot and don't ever worry about mileage and still average 18-19 mpg.

Take it to a good shop and have them look if you're not mechanically inclined.

 

Full maintenance including changing out all of the fluids. Check compression, might be a busted up tired motor thats been turdbo nossed suparchraggered overheated ***** of a z. Never know.

 

I drive with a lead foot and get 17.8 mpg with city driving...

The engine could be in bad condition. How many miles ?

 

124k miles I bought it at 120k miles. If I drive it with a lead foot I can sometimes get like even 9mpg ha

 

Hmmm I don't know what you tried yet but..

-Clean the MAF sensor
-Get a new air filter

-------------- Reset the ECU and then see if that helps.

My z was feeling sluggish because the MAF was never cleaned.

 

I've bolded what is a major problem. If it takes a long time to get up to that speed, you definitely have a problem that bolt on upgrades will not fix.

I would try replacing the air filter, clean the MAF tube, and add some SeaFoam with your gas. With mileage like that, it's a good idea to clean out a lot of things in your engine bay and maintain the car more often.

 

I'm thinking a tune-up won't help him much. I'd start with a compression check (doesn't cost much) and go from there. I wouldn't be surprised if his compression is pretty far off.

 

You need to do a compression test. Look for some consistency among the cylinders. If compression is good, you should change your spark plugs since you'll have to take the old ones out anyway for the compression test. Also, sometimes a weak knock sensor won't throw a code but it'll rob your power. One of my buddies changes his knock sensor out every year regardless of whether he gets a code or not.

 

And a +1 to what pbn posted.