bigbass37

Just bought a mint 1991 944 S2 with 39,500 mi. This is my first Porsche. Seems like vibration might be excessive when idling. Haven't found a local independent repair shop here yet. Any thoughts would be appreciated!

Sami951

Could well be the motor mounts, they certainly don't last forever...

The usual clue is noticeable vibration on idle, which then dissappears once the revs go above 1500 or so...

Another usual source of excessive vibration is the balance shafts, apparently it's very easy to get one (or both?) timed 180 degrees off.

Hope this helps!

bigbass37

Motor mounts were replaced 14 months ago. Would after-market mounts cause this vibration?

Alpine951

I have had aftermarket mounts fail 12 months later.

oi-punx

Yes,

They are most likely toast. I had my motor mounts replaced about 16 months ago. They have less than 3k miles on them and they are already bad.

Based on the price I paid i'm sure the mechanic used aftermarket parts. I think i'll go with the genuine thing next time.

Chris_924s

Sounds like mounts to me...

The motor mounts may well have been replaced with aftermarket units- or even solid mounts. I've heard the aftermarkets last a year or so. best way to check is to measure the distance between the crossmember and the oilpan-
quick check- if your hand will almost fit between the pan and crossmember the mounts are probably ok.

Welcome! Pretty soon you'll wonder why you waited so long to get one!

SoCal Driver

Did the PO have the belts, tensioner pad and cam chain replaced recently?

If not you had better do it now.

When these fail you will see a plus $3,000 bill for fixing the head.

Yeah I see where there is about 40,000 on the O-Do-Meter but these items are rubber and plastic and will age wither you run the engine or not.

Timing belts should be replace every 4 years regardless of mileage. The tensioner pad is supposedly a 90,000 mile item but many replace it at every other timing and balance belt replacement.

Sasha

I replaced motor mounts about two years ago. I bought an aftermarket ones from (it I am not mistaken) Pelican Parts. They are still ok. No being hydrolic mounts, the vibration is still there but much better than with failed stock ones. In my case, just the exhaust side mount failed (I assume due to higher temps on that side). Driver's side mount was fine. Hayes manual (as well as factory manuals) outline how to easily check the stock mounts. It invoves measureing distance between the engine support (top) and chassy mount point(bottom). Replacing the mounts involves jacking up the engine and lowering cross-member.

Hope this helps.


Thanks.

SoCal Driver

Stick your finger between the crossmember and the bottom of the pan. If only your finger tips can fit then you mounts have colapsed.

Should be sufficent room to get your had in up to the knuckes if not more.

bigbass37

Belts and chain replaced about 16 mo. ago by previous owner. I have repair invoice. 1991 944 S2.

SoCal Driver

Nothing said about the tensioner pad?

Might be worth pulling the valve cover and check the tensioner pad.

As to the vibration at idle. Take a long look at the repair order and see if the front seals or the water pump were replaced. This would mean the balance shaft pulleys were taken off.

There is a tendency to get the balance shaft pulleys on about 170 degrees out. The pulley has two keyways so it can fit both the shafts. Will result in a high pitch vibration at idle increasing to very uncomfortable at 3,000 rpm.