engine speed vibration

[mcneilbmx]

i have a 93 talon es and when i accelarate up to 3000 rpms my car vibrates. once i pass about 3300 rpms it goes away. it happens on accelaration and decelaration. if someone can help me find out what is causing this it would be greatly appreciated.

 

[brute]

You may have loose motor/transmission mounts (as for the acceleration, anyways). On my car, it shakes really bad when i decelerate because my brake rotors are warped. You can either buy new ones or hope your local machine shop can resurface them level.

 

[mcneilbmx]

i just put on new rotors and pads not to long ago. its made the vibration before then also.

 

[Mr4G]

Also make sure to see if you lug nuts are loose. If this is so your car will vibrate at lower rpms and it will go away at higher rpms. It will also rebrate when you get off the gas. good luck

 

[mcneilbmx]

the lugs are at factory specs. it makes the vibration when the car isnt moving also.

 

[VelocitàPaola]

Do you have a CEL? You could be misfiring... check the plugs for fouling - replacing them couldn't hurt in any situation.

 

[mcneilbmx]

im kind of a newb what is CEL? but ill try replacing the plugs.

 

[VelocitàPaola]

A check engine light (aka MIL [malfunction indicator light]). Replace the plugs and see what happens.

 

[mcneilbmx]

ok thanks that was kinda a blonde moment but nope no CEL

 

[VelocitàPaola]

Is it vibrating at idle too?

 

[mcneilbmx]

nope its only when the engine is reved up to 3000 rpms

 

[VelocitàPaola]

That makes it sound less like fouled plugs... but change them anyway just to be able to rule them out. Other than that... are your tires in good shape? How about the motor mounts? Could also be the balance shafts if you've replaced your clutch and flywheel (your profile mentioned it...). Check out this thread, it seems similar to your problem.

http://www.dsmtuners.com/forums/showthread.php?t=210859&highlight=vibration

 

[mcneilbmx]

well if it is an out of phased balance shaft wouldnt removing them cause a vibration also

 

[mcneilbmx]

i also forgot to mention that my rpm needle bounces around in the area between 3000 and 4000 rpms

 

[VelocitàPaola]

Removing them would eliminate the vibration.

 

[mcneilbmx]

so what would cause my needle jump around in those rpms

 

[VelocitàPaola]

I'm not sure, this one's got me... perhaps you've got a few things that need replacement/cleaning. Look for vacuum leaks, and clean the throttle body if you can. I'm not sure if that'll help though. Good luck.

 

[mcneilbmx]

well my car has been sitting since august becuase i blew the transmission so maybe i just need to clean some things up. ive also noticed something weird about my alternator belt whenever i put a new one on it gets shredded up and it throws it off. ive done the break in and let the car run for a bit and then check the tension on it agian. but after it throws the new belt i can put the one that came with the engine on it and it stays on. i ways starting to think that i might have a bent pulley but when i watch them when my car runs but i cant tell. could this be the source of my vibration?

 

[VelocitàPaola]

Very possibly... I'd look into the crank pulley first, then check out the alternator pulley. Damage may not be apparent, so if possible, replacement would be the best bet.

 

[mcneilbmx]

should i get a underdrive pulley or should i just go with oem

 

[VelocitàPaola]

Underdrive will help performance a little, but obviously they're more expensive as well.

 

[Defiant]

Your rear balance shaft is out-of-phase.

 

[mcneilbmx]

so does that mean that i have to replace it or is there something else i can do to fix it?

 

[Doug99RS]

You may have loose motor/transmission mounts (as for the acceleration, anyways). On my car, it shakes really bad when i decelerate because my brake rotors are warped. You can either buy new ones or hope your local machine shop can resurface them level.

I'm with Brute and Defiant on this one. I don't feel as though it's a misfire condition based on the limited information provided. Sounds more like there's a vibration in the engine that, at the 3k rpm range, is most pronounced. It could be worn motor mounts (put in some eurethane mounts and really get your teeth chattering) or as Defiant said it could be a balance shaft out of time. This will cause a bit of a rough idle and then depending on position of the balance shaft you could have a vibration at one or more locations in the rpm range.

A balance shaft out one tooth or so can cause up to 8-10 lbs of out of time rotational mass. Get it out too bad and that weight can turn in to as much as 80 lbs which will shake the engine to bits.
Doug