Whats up guys your help is very appreciated. Ive read so many threads to try to find the right direction but with no fault codes i am lost!

2003 nissan 350z 119k on the clock
NO CODES currently
Car just feels very slugish , louder than normal. Gas MPG is down to 11mpg
I did have intermittent cutout while driving a while back maybe 5 times randomly suggesting a Cam sensor or crank sensor symptoms.. But NEVER A CODE for it..
I have only gotten one code for System to lean bank 1 and then it went away.

I have changed plugs
Air filter
CLeaned MAF
Injector cleaner
ECU reset.

Also in relation to the sluggish accel (Feels like i lost all torque) Once i push the pedal passed 60% to accelerate it almost feels as if there is a hesitation like i have my foot on the brake pedal... No idea were to go at this point. FSM has many procedures but i do not have Consult to play with.

HELP!!!

 

What brand and model sparkplug did you change to?

 

NGK Irridium
PLFR5a i believe

The recommended plug

I do have the leaking Valve Covers but i really dont think that alone could make the engine run this poorly.. Also about a month ago i started it up to go home from work and it sounded like it was running on 5 cylinders almost like a subaru.. I drove it and it diminished.. Once again no codes ever popped up

 

Your leaking covers can cause a misfire. Smoke test is your best friend.

Do you have cipher or any datalog capabilities? You will be suprised how much troubleshooting you can do just by datalogging. I was running 16+ afr's with just testpipes and exhaust.

Generally, a louder than normal exhaust is most likely the result of a leaner mixture. Most exhaust leaks won't throw codes, and neither will small vacuum leaks.

A while back I filled up at a sketchy BP (93 oct) and quickly after, cut power/slammed-on-brakes 3 times in a 10 mile stretch. I've seen somewhere on BITOG a fuelfilter packed full of diareha. All it takes is one bad fill-up to cook our fuel pumps and clog the internal filters. I wouldn't rule this possibility out.

 

I had this problem before. turned out to be the knock sensor..

 

Thanks for the input , the only logging I can do is with the torque obd app. I replaced the MAF and it smoothed a tad but still hesitating with extreme power loss. How would I go about checking the fuel pressure? Which vacuum line is best for checking vacuum too.

 

Im getting the exact issues. I replaced all coil packs, knock sensor and harness, cleaned maf and it g p.o. t 90% better but misfire still there. I do have cipher but dont know how to datalog.

 

Poking around under the hood and noticed 3 of my center plenum bolts were loose... Gas MPG went up and car smoothed a bit. Then i put new plugs in again this time plfr5-11's i had AIX-11. Gas mileage went from 18 back to 14mpg.. WTF lol