Hello,
I have a 1990 300zx TT that I got probably a month and a half ago after selling my 350z. Now this car was sitting for a few years so it required a decent amount of work and I am still trying to get this car to 100%. Now I am currently having an issue with my engine.. It has around 100k on it(swapped out to jdmtt-car was originally a tt) and before it sat the timing belt was changed probably 1-10k miles beforehand.

The car drops and rises and drops in rpms when i first start it. It takes a few seconds for it to even out and it smells of gas when it's started.. There are no noticeable gas leaks. The engine also sputters or putters whatever you want to call it. It go bumbumbumbubmubmbumbumbubmubmubmbumb like it has a huge cam in it. (The car is obviously missing) And it also backfires after I let off of full throttle at certain rpms in certain gears or after I'm 3+psi of boost. So the a/f ratio is probably wacked. I am wondering what might fix this problem so my car can regain full power. It has clogged cats (which are being removed this week) and my passanger side o2 threw a code once and failed the ecu test. I am replacing that tomorrow morning(hopefully fixes it) Now this is what I have replaced so far. Also cleaning the MAF soon.

-Spark Plugs
-Fuel filter
-Fuel PUMP
-Starter(blew out on me)
-Throttle position sensor(was all corroded)

Also has 15lbs boost jets already in it when i got it.

Could it be my CAS? Would that fix my issue? I am not sure if it is an injector problem or not.

PLEASE HELP!

Any advice is appreciated, thank you so much! (Can provide video if needed)

 

Check injectors first. Pull out plugs from injectors to find out which one is not good.

 

I had this same problem when I first got my z. People tend to break off the tabs that hold the plugs that plug into the coil packs in place. On my car, most of the tabs were broken off, causing a dead cylinder on each one of the coil packs that weren't plugged all the way in. Try pushing on all the plugs and if they push into the coil packs then that was your problem! If not, it looks like you'll have to dig deaper. I hope this helps you out! If your tabs are indeed broken off, you can order a new set from Z1motorsports.com for fairly cheap.

Good Luck!!