i just bought my first Z today. its a 1990 N/A 2-seater 300ZX. i hope i can find some good help here! so i got this car, and from the minute i stood beside it i could tell that it was running rich. soot build up on the bumber, fuel smells, and an estimated mileage of 17 mpg out of this N/A with 150,000 miles. i have a few ideas about potential causes. O2 sensor, spark plugs, air filter, and if the car hates me, maybe leaky fuel injectors. i don't really know how to go about tunign the car, seeing as my last was a "78 MG Midget. any advise on fixing this problem would be appreciated. i don't know how to find which thing it is. anythign else to look for on a 150,000 mile car would be appreciated.

 

17mpg is actually whats expected on the NA's believe it or not, you can do spark plugs and O2 sensors, but you cant tune these cars.

 

well i guess i can believe that. thanks for the response. i'll give those a try and see if the fuel smell goes away.

 

low 20s is normal on an n/a.

just go thru the list you have, and hopefully that will fix it.
also, run a diagnostic and see if that brings any problems up

 

To add to your list....a few more basics....new fuel filter and clean your throttle bodies. Just don't go cheap....use OEM wherever possible. I would be willing to a venture a guess that the PCV valves are in need of replacement as well. A little Sea foam wouldn't hurt either.

Other than that....enjoy the ride.

 

yeah, thats what i did on my car when i had teh Z32, ran seafoam through both sides of the plenums something else and carb cleaner to. makes lots of white purty smoke lol. theres a write up on twinturbo.net on how to clean out your junk in the engine/plenum/throttle boddies/valves and what not

 

thanks for all the ideas. what and where are the PVC valves?

 

well i think i fixed it. incase anyone was wondering, the temp. sending unit wiring harness was pretty burnt up. a little dielectric grease and a bend of the pliers and my carbon build up problem is gone.