944 S2 engine problem

[z3944]

The engine vibrates quite badly between 3000 and 3400 rpm. It doesn't affect performance or ride or make the car shake, but I can feel it through, and see it on the gear stick. Up to 3000 it's very smooth, above 3400 it's very smooth - but then I'm also speeding so I only did it once to test the engine! The vibration occurs whether moving or stationary, and with the clutch in or out. Any ideas please? Thank you.

[tertius]

Haven't a clue really, but when were the belts last changed, and have you checked the engine mounts?

If it happens when the car is stationary, and clutch in or out, it can only be the engine itself or its mounts.

[z3944]

Everything has been changed and done when it's supposed to be. The car is well looked after. One owner before me, I've had it twelve months and done 16000 miles in it (because it was off the road for three months). It has FSH, and at 155000 miles has original everything except brakes and tyres. You might be right with mountings.

[stevep2000]

Have you checked the Balance shaft belt is ok? Has it just started or been like that since you've had it? I've heard it's possible to put the Balance Shaft pulley on the wrong way, causing the timing of the balance shaft to be out when everything still lines up.

[z3944]

It's only started a week or so ago. I only really noticed it as I could feel it while accelerating (if I can call it that) through the gears - I usually change between 2000 - 2500rpm, but if I'm feeling daring I will occaisionally go above 3000 rpm.

[Boosted LS1]

I'd look at the belt tensioners to see if they've come loose or gone slack, check the bolts to.

Boosted.

[HAB]

Sound like a possible balance shaft belt failure. That big old four pot vibrates like a b*stard without the balance shafts doing their job.

[hartech]

If a ballance belt is miss timed - or goes out of time - or snaps - the worse revs for vibration resulting is almost always around 3800 - 4000 (and a much smaller vibration at half those revs).

It can be miss timed by one pulley being assmbled on the wrong one of 2 keyways, belts cam come slack and slip round a few teeth - or it is piled up and possibly interfering with the cam belt and might then snap that = big costs.

Get it checked out because the vibration will eventually snap the oil pick up tube = no oil pressure and an expensive rebuild or repair.

Baz Hartech.

[z3944]

Thank you all for your advice. I will investigate and update with findings later.

Thanks again.

John.

[willdew]

My first thought was engine mounts.
My train of thought is that at certain rpm the whole engine/drive train resonates, so the vibration is more evident. Have you revved it through the range with the bonnet open and someone observing if the engine has any noticeable movement at those ranges?

If you have no luck, I very highly recommend EMC engines in Birmingham to have a look for you. They're an engine builders rather than a garage and specialise in 4 cylinder Porsche engines.

[doctorpepper]

willdew said:

My first thought was engine mounts.
If you have no luck, I very highly recommend EMC engines in Birmingham to have a look for you. They're an engine builders rather than a garage and specialise in 4 cylinder Porsche engines.

I'd agree whole heartedly with that....

You could also just give them a call and decribe your symptoms to Kevin and he'll let you know exactly whats wrong with it... 0121 3282225

just tell him me an Will sent you!

[z3944]

Thanks for all the advice. Checked everything out. All the timing was spot-on, but the balance shaft belt was loose. Adjusting the belt has reduced the vibrations, or rather narrowed the range to between 3200 and 3400. Doesn't happen before or after those revs. Any ideas as to what else is a common problem that may be contributing to this (now improved) problem?

Thank you

John.

[stevep2000]

If the vibration is not that noticeable, only through the gear stick as you say, maybe it's just a 'feature' - I notice mine vibrates a bit around those revs. They are big 4 pots after all, so even with all the balance shaft tech they'll never be smooth as a nice six. Also, maybe as the balance shafts / bearings wear with age, they don't 'balance' as well as they did when new? Are you able to compare with another S2 locally?

[nick_968]

They are perfectly smooth if everything is right. It sounds like you have something wrong to me, probably the balance shaft is 180 degrees out of alignment which is an easy mistake to make. This can potentially crack your oil pickup tube which will then lead to oil starvation and fluctuating oil pressure which in turn will destroy your engine. This has happened to more than one 968 owner that I know of. Get the balance shaft alignment checked asap. The fact that your belts were loose probably means that whoever did the belts did not recommend them to be retensioned after 1000 miles or so. This normally means they are not that familiar with the cars. If this is not the problem then check engine mounts but they would have to be really shot to cause that bad a vibe at those revs as its normally more noticeable at tickover.

[hartech]

Nick is right but not explained why. The shafts have one keyway but the pulley has 2. If you take one off and the balance shaft has the weight at the top - then when you are not looking it can turn under its own weight 180 degrees and you can then fit the pulley on again with all the timing marks lining up - but the shaft is then 180 degrees out of phase.

So it is not just the timing marks that must be in line!

Baz Hartech

[stevep2000]

Maybe I have the same problem myself then! Vibration is not really that noticeable unless you have your hand on the gear stick. Just spent a packet on a top end rebuild as well, so better get it checked out.

[hartech]

The 944's had a nylon bush at the front and rear of the gear change shaft and this damps out any vibrations, but the 968 has a ball joint that - when it comes a little bit loose can rattle and allow the gear change shaft to vibrate a bit.

Which problem you have can probably only be determined by someone who is used to the cars and by feeling the amount of the vibration to work out which is the most likely cause - but I have seen a lot of cars with the pully fitted the wrong way round on the shaft, but the timing marks lined up - but then I am used to what that feels like and it is difficult to know how much vibration you have.

Baz Hartech

[z3944]

Nick is right. When they are set up right the engines are amazingly smooth. The belts were fitted by JZ Machtec. They were checked / tensioned at the necessary mileage post-fitting. I said the belt was 'loose', but it wasn't flapping around or jumping - it just needed a slight tensioning. The vibration is now only at 3200 - 3400 (it was 3000 - 3400). Unlike other threads I have read it does not occur before or after this rev band. The problem has only recently started. If the cam had been incorrectly lined up when the belt was fitted then I assume I would have had the vibration from the beginning. The engine itself does not move anywhere when you rev it, i.e. solid as a rock - so I assume the mountings are fine.

[stevep2000]

I may be wrong (again!), but I thought I'd read somewhere that no movement is a problem, i.e. the mount has collapsed & is not insulating the engine movement / vibration from the body?

[johnmaddox]

I had this on a 944 years ago. In my case it was a soft engine mount.

The engine drops slightly and this allows the gear selector shaft to vibrate on the torque tube housing.

Rather than change the mount I raised the gear sector shaft by placing two large rubber washers under the mounting at the gear lever end.

Sounds rather Heath Robinson but it worked brilliantly and was a permanent fix for about 50p !! No more noise/vibration and a completely vibration free gearlever as well. Thinking back it was amazing how much better the whole car felt afterwards.