rmoleman

86 951 bought with 45k mile currently 58k (one owner car)

I did a bunch long term maintenance since I bought the car 12 months ago:

New trimming belt and rollers
New water pump
New motor mounts
Replaced most of the gaskets in the exhaust system to fix multiple leaks
New plugs
New wires
New distributor cap and rotor
New fuel filter
New Pads
New Rotors
Changed brake fluid

It pulls strong, no oil smoke, almost zero oil consumption but there is one problem.

Lots of vibration at idle. The idle speed is correct and stable. As RPM increases the vibration is less but it can still be felt when driving. There does not appear to be any misfire and all the plugs looked good when I changed them.

Any ideas on what to look for are appreciated.

turboted

Hmmm...I would check to make sure balance shafts are properly aligned, especially if belts were recently replaced. This could be the cause....

rmoleman

What is involved with checking the alignment of the balance shafts?

mortymower

If you pulled the balance sprokets to change the seals, you probably flipped your balance shafts. I did it the first time i did the belt and rollers and it shook like crazy.

read here

clarks-garage.com/shop-manual/eng-08.htm

to see what im talking about, very easy to forget.

mortymower

god i have to type faster!!

rmoleman

Any one have pictures "balance shaft sprocket covers"?

mortymower

its in between the shaft bolt (on the end) and the shaft sproket. Its like a big washer for the shaft sproket, ill try and get a pic in a sec

turboted

The balance shaft sprokets are the gears on which the belt spins. Each one has a notch on the back side of it. These notches are supposed to line up to marks on the timing cover. Clark's garage offers a great explanation...I have pics, but not with me now. Will upload later if possible.

mortymower

here, the arrows point to the covers attached to the sprockets

lejams

Motor Mounts can cause this too. Once had a brand new one that was defective and caused significant vibrations at idle. Scratched the head for a while because you wouldn't have thought a brand new mount would be failing.

rmoleman

Thanks for the pictures. This looks like it is going to be hard to get to with the motor in the car. Has anyone checked the alignment of these shafts with the motor in?

NeoRules

is it vibrating at all rpms?
check the above but I had some bad vibration up to about 3K rpm or so and it eventually turned out to be mucked up injectors....
sometimes it seemed better than others...
Good luck JC

mortymower

Yea its not hard to check the alignment of these guys while in the car I just had a better shot because mine is out right now. The top is super easy and if you have trouble with the bottom for some reason, just grab a handheld bathroom mirror and put it down there to get a better look.

Ski

get some white touch up paint. paint the indent on both the gear and cover, bottom paint the line and the indent on the gear.

put the car on TDC and check the upper BS gear. The notch on the back of the gear should line up with the indent on the back cover.

I'm just asking, please don't be offended, you did double check TDC when you put the timing belt on and you do you have the wires in the correct order?

mortymower

but I would take the sprockets off as well to make sure they are even on there correctly. I had mine flipped 180 and it lined up perfectly with the belt covers but the actual shaft was 180 wrong