Engine Vibration

[Japtastic-UK]

I have a problem I hope some one can tell me what it is.

The vibration starts at around 2500rpm, but could be there before but no noticable enough, doesn't matter weather the clutch is in or out, moving or stationary, it did happen after doing lots and lots of doughnuts with a diablo in a tunnel, this is when my gearbox failed as well, don't know if it's connected or coincidence?

The vibration stays throughout the rev range and makes the car feel as if it doesn't want to accelerate rather than before it wanted to go.

It was bouncing of the rev limiter quite a lot, I know it's bad but the tempatation was too much. I've heard oil pumps don't like this, but could that cause such a vibration?

Cheers

Stewart

Edited September 2, 2007 by Japtastic-UK

[NUTSGTR]

I had a bad vib around 1500- 3000rpm in my rb26 then not so bad but still noticeable through the rest of the rev range. Turned out it was the harmonic balancer bolt had come loose (or maybe the previous owner didn't tighten it enough). Also a definate lack of power in accordance. Anyway I spun the balancer and chewed the keyway on the crankshaft. Obviously harmonic balancers are there for a reason; they add weight where there isn't enough and take it away where there's too much. When they spin they kinda emphasise the bad and reinforce the good which doesn't work. Well it was kinda expensive...like new crank, balancer and bottom end freshen up expensive. Have also had the oil pump go as well. Doesn't vibrate just gives no oil pressure and starts to get a little sluggish. Check ur harmo bolt for starters i'd say.

[Japtastic-UK]

That's definantly fine as I have just replaced the timing belt and tensioners, so it's all torqued up, the vibration was there before this btw, I changed that lot to see if the vibration would go away but it didn't. Thanks for the input anyway. Can harmonic balancers fail and cause this?

[NUTSGTR]

The standard balancer has rubber mounted v-groove pulleys which i've seen compress on 1 side presumably (correct if i'm wrong) from sitting for years at a time on an engine that has rarely been started, such as in japan pre-export. The belts are obviously still tensioned and are continually pulling in 1 direction on the balancer, the rubber goes hard over time, and you are stuck with an out of balance balancer. Don't know about that if urs failed after doing donuts. Have you done a compression test on ur engine? If 1 of ur cylinders has lower comp for some reason it could be vibrational. Could also explain the lack of power. Just a thought.

[blind_elk]

Are all six cylinders firing cleanly? Because I'm guessing you've pooped a piston, and it's only running on 5.

[Japtastic-UK]

Compression is good across the board, defianantly firing on all 6, it still pulls like a train but not like before, I'm in the middle of changing my gearbox and I'm hoping that will fix it because it was very screwed. I'mm hoping that the gearbox can cause this even with the clutch depressed?

[Japtastic-UK]

Just to let you know changing the gearbox has fixed everything my god I'm glad, she feels perfect in every way now, pulls hard and fast and nice and free flowing Can you tell I'm happy