Hello, I have a Nissan r33 skyline gt manual with 113800 km. It has a shaking/vibration/slow acceleration problem over 6000 rpms since iridium spark plugs put in, and new stock injectors. I also feel horrible issues now at all times, it can't go up to 4k without vibrating on 4th and 5th gear now. Just had the rotors resurfaced, and am had trouble completing 4th gear before and after, and shit acceleration up to high speeds now. It was just working before the dealership put in new injectors, don't know if they beat on it cold or what. Theres a noticable metal noise and wheel vibration when coasting down without clutch engaged. I didn't ever notice that issue until I brought the original driveshaft for inspection from a mexican driveshaft shop and they said my u joints are good. A phony aftermarket one I tried from south carolina almost destroyed the car with vibrations. Had to return that, and make them buy a label for it back. They didn't fight my credit card case.
Is this noise/vibration there if you run the car up to a high speed, then put the car in neutral and turn off the engine and let it coast down from a high speed?
Yes i have a vibration metal frequency coasting down in neutral with no engine or trans engaged
Multiple problems.
Make sure spark plugs are firmly connected. Same with injector wiring...the connectors become brittle with age. They may of broken one and not replaced it.
Metal noise could be bent brake rotor dust shield rubbing. Vibration from improperly reassembling rotors to hub.
Driveshaft...2 piece setup...carrier bearing (hanger bearing) failure, out of balance...look for missing welded on balance weight on steel driveshaft....impact damage on carbon fiber or aluminum driveshaft. Failed cv joint/ujoint.
I have brand new injectors, a rotor resurfacing, and I'm no noob with a rubbing dust shield. It's got a vibration problem coasting down in neutral, and accelerating. I installed a new center bearing, tore down and reassembled again, the u joints are non servicable. Should I just order a new $900 shaft or find a shop that can do non servicable u joints better than stock to last?