Help! What's gone wrong? Horrible noise, then cut out

[Trevor68]

Hello everyone,

Looking for some help and advice - My '86 944 Turbo developed a horrible rattling that sounded like it was coming from the front cam housing/distributor area at idle. It would rise with engine speed until about 2k-2.5k rpm when it would disappear. The noise is what I'd imagine a spanner in a washing machine might sound like.

Being only 1/4 mile from home I limped back and popped the bonnet to investigate. As I was investigating the noise ceased and the engine died. It hasn't started since. It turns over, with the alternator and power steering belts appearing to turn as normal.

The weekend previous it had done 200 miles in the Lakes without drama and I'd used it the day it occurred but the noise wasn't evident until I started it pretty much from cold the second time and had traveled about 200 yards.

Initially thinking the noise was dizzy, rotor arm, possibly the dreaded DME relay and so proved spark to the coil lead, swapped the dizzy cap and inspected the rotor, at the time hoping it was the rotor screw or rotor arm bolt I'd read about but no joy all looked good and solid, a look through the little hole on the cam tower cover and the the belt 'looks' OK and a new DME all to no avail. Cranks but no start. Good smell of fuel when cranked too.

Back to the forums and read all about timing belt slips and breakages, 'spun rods' lifters failing' and other terribly expensive to repair problems as well as easier to palate, reference/speed sensors, heat shield and exhaust rattles etc. So now I'm a little scared and confused and don't know what to do next!

What should I look at or do next in order to diagnose?

Apologies for war and peace! [8|] and thanks in advance for any help

 

[PSH]

Hi Trevor..

Sorry to hear of your woes...[&o]....

Was the noise still there when trying to turn the engine over or has it now gone completely?
You say you have spark at the coil but make no mention of the plugs?.. I would take out all the plugs and examine them closely. The noise you heard could be a stuck tappet, it could also be a damaged plug or worse, however if the noise has now stopped I doubt it's something in the worse category however it can not be ruled out.
Was there any other signs before this happened, running rough or any other unusual noises?
Also what plugs are you using?


Pete

 

[Trevor68]

Hi Pete,

Thanks for the quick reply...

No sign at all of the noise when the engine's turned over.
I haven't checked the plugs, I'll do that soon as, probably tomorrow now and check for spark at the same time.
No obvious signs although it would idle a little rough occasionally which was fixed by reconnecting a vacuum line
Not sure what plugs are in, think there NGK?

 

[PSH]

Not sure what plugs are in, think there NGK?

I was wondering if they could be Iridium plugs,, NGK do make these as do other makes, I had an NGK iridium plug fail myself which at first I thought was a stuck tappet as the noise was very similar. I would check the plugs first before checking for spark, in particular for any signs of missing ceramic around the electrode. iridium plugs are known to fail here so much so that I know of a dyno that refuses to run any cars that have these plugs fitted.

Pete

 

[Trevor68]

I'll get them checked out and report back - what's the fix if it is a failed plug?

Thanks

 

[PSH]

depends on the damage.. mine put small dents in both the piston and head plus a very small score on the bore, having said that this had no effect on the cars performance.
It happened the morning of a dyno day , the engine sounded terrible when started in the morning.. I thought it was a stuck tappet ( sounded the same as a friends 944T when one of his tappets got stuck which then cleared on the way to my sons garage to be looked at, so I am familiar with the sound that a tappet makes) I kept the engine running in an attempt to get it moving ( normal practice) it took longer than I expected but did eventually clear( the ceramic that broke of the spark plug was either pounded to bits or flushed down the exhaust). I say it had no effect on the cars performance as the car achieved 368bhp on the dyno which was exactly the same as when it was mapped a year before. I only found out about all this when the head gasket blew a few months later and on stripping down the car the damaged caused was discovered.

One of my many sargers of Porsche ownership...[]

 

[Frenchy]

Pete,you have got me checking plugs tomorrow, sure i have just fitted irium plugs to my car (Turbo S) ,just dawned on me i will have a look at the invoice and see if that tells me first !
Jim getting the 220 t looking right !

 

[Frenchy]

Trevor ,
Forgot to add to the answer with what you are looking for, with all honesty sounds like something with mettalic rotating parts, cam,balance cams,tensioner,rollers, has let go.........................certainly hope not !
Check for fuel at an injector first, take each plug out 1 x 1 then check for fuel at each one tells you that each injecter as ok.
Have a spare dry plug ready and check out each plug lead firing if they are OK you need to get the sensors at the back of the engine and check them out, they sense correct rotation speed of engine then switch the dme relay to switch and provide fuel and ignition.
Still no clues, then start stripping down from the top cam housing etc, good luck and keep us posted.
Jim.

 

[robsangster]

Pop the cam cover and check those springs, possibly dropped a valve?? Very short term running problems prior to engine dying was what I suffered with my S2 (although I wasnt running it at the time - she was!) broken spring, leading to snapped valve, leading to punctured piston.... wrecked head.... the list goes on! Obviously I certainly hope that is not so in your case. Will be interested to know the result on this one!

 

[xenon]

Remove the cam belt cover too. It's not unusual for the belt to fail by shedding teeth without actually snapping. A cursory glance all looks ok but the crank pully spins without turning the belt.

Good luck.

 

[Trevor68]

Thanks for all the responses everyone!

I didn't get chance to do... well anything car related over the weekend but I'm poised to start hopefully tomorrow after work.

First, remove the spark plugs, inspect (noting if they are Iridium or not) and shine a torch into the cylinders. If nothing obvious I'll move onto the belt cover, remove it and give the all the belts a stern looking at. Next the the cam cover, how easy is it to 'pop the cam cover'?

Actually, first I'll crank it hoping it's cured itself! Ever the optimist! []

 

[Frenchy]

Trevor,
As such it is not a cam cover in the traditional sense but a cam housing by that i mean the cam lives in there along with the hydraulic followers, turn the engine round on the crank pulley a couple of times with the covers off to enable you to see everything pulley wise is moving as it should.
Take the engine to TDC visible on the flywheel inspection hole then loosen the cambelt to allow you to start taking the cambox off, fuel rail and injectors to take off first, be careful when you lift the cam box off as the hydraulic followers will want to fall out and possibly get damaged at 50 odd quid a pop ! lay them out in order so that they go back in the right place.
Just a tip before taking the cam belt off the top pulley mark the belt and the corresponding tooth on the cambelt with some paint to make sure they go back together in the right place.
When replacing the cambox put a thin smear of grease /vaseline around the edges of the followers to help them stay in-situ.
Do keep us posted.