goingboeing737

The main issue with the new car is a bad vibration right at 4000 rpm. PO said it started right after the water pump and belt job.

So, logic would lead one to think balance shaft belt.

Geo, Jenkett944 and me pulled the covers today and went exploring.

Alas, the belts, rollers and timing seem to be right on.

We buttoned it all up and went for a test run. I had not run it up to anything near 4000 rpm before this, as I wanted to check the belts beforehand. Sure enough right at 4000 rpm it shakes big time. Gear shifter, gas pedal, whole damn car, you can feel it in your bones. Feels very mechanical, not like a fuel or electrical related issue and only does it under a load, not when you rev the engine in neutral.

I just drove it 20 minutes. Runs like a top at anything under the 4000 rpm. Although it feels a little sluggish compared to my other 84, but that could just be tune up related stuff or that it has sat for a while.

SO,,,What next ? Torque tube ? Anyone experience what a "bad" one feels like ?

PO had a used tranny installed. Don't know why. Could something with that process/repair done wrong cause this ? One of the PO's work orders had written on it "Balance Shaft is Bad". We kind of wonder how they would determine that without an engine teardown.

Has new half shafts/CV's, rear wheel bearings and a complete clutch job, Any of those items possibly related ?

We will probably go back in, remove the balance shaft belt and drive it to see if it changes the situation. Before that however, I thought I would post it here to see what y'all might think.

Geo & Jenkett944, feel free to add any feedback from your visual or driving experience with it today to help explain the sensation/problem.

Chime in, think outloud, conjecture or guess....all thoughts and replies welcome

iloveporsches

Balance shafts are out of time by 180*. 50% sure.

edit: the other 50% is I'm talking out of my ***, and have no clue what your problem is

edit-edit:changed statistics after you made your second post

ERAU-944

conjure what? if i could conjure the answer for you i would. alas, i cannot, therefore, i conjecture...

i think a balance shaft is 180 out. its still possible, i think, don't they have two identical markings?

goingboeing737

This was what we were expecting to find.

BUT.....

The "O" and the "U" seem to be in the correct positions and the marks line up exactly.

Wouldn't they be off it it was out 180 degrees?

edit...thanks Erau, spell check only works if I type in the correct word to start with...

iloveporsches

Check this out, if you haven't already:
http://www.clarks-garage.com/shop-manual/eng-08.htm

Cass944

i had my bottom roller on bachwards. the face of the roller was facing toward the engine, an easily made mistake i guess. but it made it so that the roller was about 6 teeth off. and I had the exact vibration you speak of at 4000 rpms.

if not that, in 86 the bottom balance shafts changed so that the O does not go the same way as it did in 85. so make sure that your directions you used were for the same year your car is.

hosrom_951

Take OFF the balance shafts and re-install them

I had that problem (at 3,300rpms) and everything looked fine.

After removing the belts, found that they were not installed properly........

Just double check it.

Geo

Well, that is on the list of things to do. I was certain the shafts were off, but as James said, all the marks line up. How would it be possible to get them wrong with the marks lining up.

BTW, they rollers cannot be backwards if we see the O and U can they?

Luis de Prat

Same here.

Symptoms were like this: Cruising in 5th, downshift to 4th to accelerate, and the car had no pick up at all, plus a nasty vibration.

pete944

To rule out the possibility of the balance shafts, just remove the balance shaft belt and take the car for a quick ride. The car won't idle as smooth but it won't be too bad. If the 4K vibration is gone, it's the balance shafts.

hosrom_951

BTW guys, i have an o-ring leak comming from behind the cap-to-camshaft housing....


Anyway, we took it off today, and found that o-ring needs to be replaced, anyway while looking and taking off the rotor, that allen bolt has chewed threads...........

Now this is a wild guess, but if that allen bolt thread was chewed, could that cause ANY sort of minor play/problem at a certain rpms?

I know that MAY not be related, but just a wild guess, since that bolt doesn't seem 'perfectly' bolted to the rotor..............

Luis de Prat

That's why it's important to replace all front engine seals when a timing/balance/sprocket/roller/waterpump job is done.

hosrom_951

That is what the previous owner said, and the bills say that too.........

Luis de Prat

Not to take this thread off course, but (it's a bump anyway) was your car recently switched to synthetic oil, by any chance?

P.S. Was the PO a fellow from Portugal? He had a car just like yours in the UAE and hasn't posted in a long time. Got a new FIAT, or the like.

goingboeing737

Thanks to everyone so far.

Guess it looks like we'll dive back in there and redo everything from the start.