aprotogerellis

Hi there,

Quick question... recently I've been getting a lot more vibrations at idle than I used to. Actually, this has only started happening now that the weather is cold and mostly goes away when the engine warms up properly...

Is there anything I need to be doing about it or is it normal (or could it imply I need to retention the balance belt by any chance?)

Many thanks,
Alex

Scott at Team Harco

Motor mounts are a more probable cause of this problem. I would look there first.

Makis

Balance belts don't cause additional vibration at idle even if misalligned. As said engine mounts or the engine is not running properly when cold.

aprotogerellis

Great - thanks a lot Maki (Greek by any chance?)

Any ideas or tips for:
a) figuring out if the engine is having trouble when cold
b) doing something about it?

Thanks,
Alex

Makis

Alex, you are right I am greek.
Now for the engine trouble I would expect if there is a problem it is likely a misfiring issue when cold caused by faulty ignition and/or fueling. A misfire will cause the engine to rock more then usual thus giving the impression the mounts are shot.
I would check condition of leads, plugs.
Depending on which 944 you have you may have problems with fueling mixture when cold. Not familiar with early 944 as I have an S2 though. S2 fueling problems when cold usually only caused by faulty coolant temperature sensor. Fueling is then controlled entirely by ECU.
In general if you have a cold fueling problem the car will also be difficult to start.

joonas

You can find how to check balance shaft alignment and motor mounts and lot more at following link
http://www.clarks-garage.com/shop-ma...ure-index3.htm
+1 on motor mounts

ilikepinkcrayons

what is the idle speed? if it is a cold start issue, it may be idling too low, and roughly vibrating. Is there a cold start system on this car?

aprotogerellis

Its idling at one notch under 1000 (which is 800 from memory).

Not sure what you mean by a cold start system to be honest... its an 86 turbo... I'm not aware of anything specifically for cold starting.

Thanks!
Alex

951jamie

There is a water temp sensor that send info to the DME,if faulty during cold weather it sends incorrect info to thr DME causing misfiring and rough idle.

jamie@944online.com

jdgunn

Makis, allow me to disagree. I have anecdotal evidence from this weekend that mis-aligned shafts can make the engine feel like it wants to jump out of the car. The 924 I picked up last week ran terribly at idle. The previous owner thought it was an ignition issue, changed everything out, then gave up. I popped off the covers, aligned the shafts and the car runs like butter.

Makis

Well, in my experience this was not the case. The engine felt more busy and I could feel more rattles in the car when the engine was running at higher revs (2-3k) but at idle there was no obvious extra rattles. I believe the balance shafts are meant to reduce higher harmonic vibration induced by the large 4 pot engine. They achieve this with little counter torque. I can't see how they can cause the engine to rock hard at idle. On the other hand misalligned cam timing can cause bad idle. But this can only happen if the cam belt has not been replaced properly or the belt itself has skipped a teeth or two. In this case I would check the cam belt condition, timing and tension ASAP.

theiceman

I Think I may know ths solution to both. oOn my 944 I had similar vibration at 2-3k , extremely bad. This was because the moron that worked on it had one of the shafts out 180 degrees causing the 2-3k vibration which is quite common.
If the shafts were out at different degrees ( not necesarily 180 degrees ) will casue vibration at diffferent rev ranges including idle.

jdgunn

That makes sense. I guess a recipe for vibration at idle is lower shaft off by about 315 degrees and upper shaft by about 30.

smac951

If the vibration does not decrease after about 3000 then I would say the balance shaft is mounted wrong. Cold weather aggravates vacuum leaks though.

aprotogerellis

Hmm... interesting points. The issue of course only started when the weather got cold and only at idle without anyone messing around with anything in between...

Is there an easy way to check whether vacuum leaks have something to do with this?

Thanks!
Alex