I am having a vibration problem. I am getting a strong vibration from 4500RPMs on up when under hard acceleration in 1st, 2nd, 3rd gear (possible 4th as well, I just have not checked it out). This is not dependant on speed, just engine RPM and does not do it much when I am not accelerating hard. My car does not vibrate when I am holding in the clutch and I rev the engine.

I am thinking of 2 possible things: One is that my flywheel is out of balance and/or is in need of a resurfacing. I was stupid and I didn't get it resurfaced when I replaced my engine a few months ago. I am thinking this could be causing the clutch to vibrate and transfer vibrations to the car.

The other posiblity I am considering is some sort of engine problem. I am wondering if maybe the two rotors arent getting an even fuel or air delivery distribution, causing some sort of bad harmonics but only under hard acceleration. Perhaps only one of the auxiliary port actuators are working, or maybe my computer is going bad, or bad wiring to one of the injectors? I know the injectors are still good, I bought all new ones when I replaced the engine.

Any input, suggestions is greatly appreciated.

 

I put my money on an unbalanced cooling fan...

remove the fan and go for a quick drive (not too long. don't wanna overheat) .. if the vibratino is gone, getyourself a new fan..
the smallest bit of play with the fan can create alot of vibations at certain engine rpms

 

I'd say it's the drive shaft.

 

Thanks for replying, but I dont think it is driveshaft because it doesnt do it unless I am accelerating hard. And it doesnt do it below 4500 RPMs regardless of speed. Also I was under the car today and I checked it, was stout as ever, no play at all.

I will check the fan to see if there is any play, maybe I will remove it as well and see. But again, I can rev the engine and get no or little vibration, so I don't think the fan is the culprit.

Thanks again for the replys so far.

 

Well if your flywheel wasn't balanced, then wouldn't the engine vibrate with the clutch disengaged? My old 83' would have a throttle sensitive vibration, turned out the be the driveshaft.

 

if it does not vibrate when the clutch pedal is depressed then it must be in the driveline, trans, driveshaft, rear end, half shafts, or wheel hubs or bearings. my guess would be drive shaft or u joints especially if it has high mileage. get under the car and check for loose or sloppy driveshaft or half shaft. then check the rear hubs and bearings

 

I would check your secondary injectors>It sounds like your problem starts when your secondaries kick in.Had a simmilar problem one of mine wasn't alowing enough fuel around 4000 rpm.

 

I recently got a rebuilt engine that came with a NEW flywheel

I have the same problem at lower RPM's..... I had a post on it earlier and the rotary gods said that it could be the U-joint on the driveshaft... but you said that's ok..
so the next thing to check after teh drive train is the engine mounts... loose/overtightened ones can jerk the car as teh engien moves......
Just a thought

 

I'd put money on half shafts.

 

I know this is probably too simple and easy a solution but when the car is excelerating hard the engine actually moves or twists a fair amount. Since the exhaust is hooked to the engine it does as well; check and insure you have lots of clearance around your exhaust. This happened to me when I moved my exhaust up when I lowered my car trying to get more road clearance.

 

Drive shaft U joint.


Mike

 

Problem solved. (finally) Chris Ng was on the right track. It turned out to be a bad water pump bearing causing too much play. I never would have thought that the fan could have caused that much vibration, now my car is smoother than it has ever been. Thanks to all who replied.