This vibration can't be right.

[alfadoc]

Subject vehicle '89 944S2. I bought it non-running, with the chain tensioner damage to the cylinder head. My single car shop space is tied up with an immobile restoration project, so I had a local mechanic do the head swap. He's not a Porsche guy per se, but a competent wrench who works on European stuff, mostly Saabs. We get the thing back together, and the vibration at idle is to me unbearable. I know it's a big whoppin 4 cylinder, but this couldn't be acceptable when the car was built.

The car has 122K on it, and I do not see motor mounts in the service history. An S2 did get the uprated turbo mounts from the factory, right? Don't they last fairly well?

Had the mechanic pull the balance shaft belt cover back off. I didn't crawl underneath to check the TDC mark, but he assures me it's on the mark, and the reference mark on the cam pulley is aligned, as are the balance shafts. Even though he didn't take the pulleys off of the balance shafts, I insist that he remove the bolts and washers, certain that a previous mechanic had installed the lower gear 180 out. No dice, O mark aligned with the woodruff key on the top one, and opposite the key on the bottom.

So now I'm really stumped. My old '86 944 N/A is all I have to compare it to; there is a significant difference between the two in terms of this vibration. Otherwise the car runs great, with bags of torque and power. What did I miss?

[Phantoms]

Im not sure if the S2 received turbo mounts from the factory but mine were shot at 89k when I bought my car. I would say that is a good place to start.

[flash968]

are you sure that both woodruff keys were pointing upward? this happens all the time- it's not about the O on the washer - it's about the key itself, and because there are 2 keyways, it gets people mixed up

everybody does it too - i just saw this on a car that came from a great shop

[alfadoc]

Absolutely certain.

[Rasta Monsta]

25 years old, 100k+ miles, it seems very unlikely mounts are still good.

[alfadoc]

New mounts are going in, but if it fixes it, I'll be shocked. I guess it's hard for me to imagine that they could do that thorough a job of dampening vibration.

[flash968]

hmmm - i have now had 3 experiences where people have pulled the cover more than once and thought things were right, only to do it again and realize they weren't, largely because they didn't actually pull the washers off to see the keys - might be worth a second look

[Makis]

From my experience misaligned ballance shats cause higher pitch vibrations making the engine sound busy. You can tell something is wrong as the interior trim rattles making the car sound like a banger. As you swapped the head, is possible that the cams are not aligned correctly, or even the cam belt itself is not correctly aligned. When this happens, at idle there is too much air fed back into the inlet upsetting the air flow meter and the car idle badly. Also similar symptoms you can get from a vacuum leak, so recheck your vacuum lines.

[alfadoc]

I appreciate the response, but as my original post states, I insisted that the mechanic pull the bolts and washers, even though he hadn't taken the gears off during the head install. Upper shaft, woodruff key to "O" mark. Lower shaft, woodruff key opposite "O" mark. I was there when it came apart. That's why I'm so baffled.

[flash968]

re vibration - nope - it will show up immediately at idle

re keys - it has nothing to do with the "O" - it only has to do with the key itself - the "O" can actually be in 2 locations, because there are 2 keyways, so you can have the lower key opposite the "O" and still be 180 out - the keys both need to be pointing up, not the "O"

[rick13]

balance shafts. next...cracked exhaust manifold. ask me how i know

[rick13]

[flash968]

you cannot see the woodruff keys in those shots, which is exactly the problem - it's not about the marks on the pulleys - it's not about the "O" - it's all about the woodruff key orientation, and both of them pointing up at the same time

[rick13]

hmmm...the shaft has only one key position. does the pulley have multiple slots?

[flash968]

yup - they did that so they could use the same pulley in both places

[rick13]

yikes! i guess i will find out soon enough if mine are correct. im gonna fire her up this weekend. i still say alfadoc's problem is a balance shaft. i've been there.

smith out

[Aenyone]

Not sure if you changed out the mounts yet, but I can assure you that when I did mine.... I couldn't believe the difference.
Honestly, it was like a different car.

good luck

[flash968]

i think it is a balance shaft too - i think the lower one is out of position - i've seen this too many times now, and for reasons like people using the "O" as the marker, instead of the woodruff key

[HondaDustR]

My engine mounts are more than likely original with 170K on them and, although it feels a little like a racecar at idle, the vibration is never bothersome or concerning. Most likely balance shafts. Even Porsche shops get it wrong sometimes. I've somehow managed to not screw it up yet, so I don't know what it should feel like when they're off.



Here's what they mean. Make sure both keys face up (which I believe they tend to settle in that position anyway), then install each sprocket in the slot that makes the respective alignment marks line up. The U on the sprockets are no longer present.

[bazar01]

Most likely the balance shafts, been there.

Bad or collapsed motor mounts will not generate a unbearable vibration that you described.

I zip tie both balance shaft pulleys when I take them out to keep them from getting out of position.