How goes it guys? I have a weird thing happening with my civic. 1994 civic ex has d16z6 with cp pistons and Manley rods as well as a skunk2 cam then has a gtx3076r. But the problem is; when I free rev or accelerate past 4000 or so I will get a vibration sound from the engine bay that stays speeding and slowing with rpm until I completely kill the engine and turn the key all the way back and restart it and it will sound fine again. When this happens It doesnt matter if i am making any boost pressure or not. It also sometimes throws a cel and runs super lean and stumbley until I turn the key all the way off and let it sit for 3 secs and restart then all is fine and afrs go back to normal. I can't get the cel light test to work to tell me what the code is so I don't know if that is an ecu problem or in the wiring. I think I will buy an ebay tuck harness to replace the old harness and replace the plugs with oe ones in the places that are more critical. I will try to get a video of it happening but my open downpipe makes things difficult to hear on video.

 

I'm going to change the waterpump and timing belt this week along with all the various seals from top to bottom and run it without a hood if I have to to find were the sound is coming from. I pulled a 2020 challenger r/t from dig to third gear at 5 psi stayed right next to him and it didn't do it but I free reved it later to around 6k and it did it but I shut the key off for 3 secs and started back without the vibration and cel code.

 

I dont know a thing about turbos, but with that being said, what about a bad bearing in the turbo. My theory is, a bad bearing: its not building boost until about 4000 rpm, thats enough pressure to make the turbine conk out of alignment, which would cause your vibration sound. Oil pressure keeps the turbine in that position. Shut it off, let the oil pressure drop, the turbine goes back to it original position. until the engine gets to 4k rpm.
Just a theory