philatnbn

This is on a 87 944S but I have experienced it on a normal 944 also. Sometimes when starting it will make the worst noise you ever want to hear coming from the engine, it sounds like valves hitting pistons. It only happens once, then try again and it won't do it but will be a little harder start than normal. It only happens every now and then. Seems to be more common if it is hot outside. Its not starter noise or clutch bolts hitting the starter (had that happen once).
Some details- independent of that problem, every so often the idle will fluctuate when started, seems like a vacuum leak or a fuel pressure drop due to a fuel leak. Cap, rotor and plugs changed - no effect. Next will be timing belt. Just to be sure ignition isn't bad or too far off.
My thoughts- detonation? Could it be fuel injectors leaking, the fuel vaporizing and heating up in the cylinder, then on a compression stroke, it ignites
Or could it be that while sitting the valves stick and then the piston hits them. I don't know if this is possible, there is a lot of force of the valve spring, so the guide would have to get really tight to hold it down. I don't have experience with thess types of problems, so I don't know what is possible or not, but if this is possible, the noise sounds like this.
Anyway, I think this might be common to 944's (to make horrible noise and not really be a mechanical problem but a FI/ignition problem) so I wanted to ask all the experts here. Thanks.

Der Cupmeister

We have never had this sort of problem with our '84 944, maybe the only one we haven't had ! 8^}

Olli Snellman

Does this sound comes when engine is running ? Or does it come only when starting the engine ?
If it occures when you start, there's most probaply something wrong with your starter or bendix device.
When valves hit the pistons it will cause bent valves.On S & S2 models it can destroy head as well.

Olli
'88 951

Derek H

I have had a similar experience with two of my previous 944 S2's. The first time it happened, the car had been sitting outside for a week or so without being used in cold weather (2 degrees C or so). The car started ok but it made the most horrendous rattling noise imaginable...like the worst London diesel taxi, with every bearing in the engine removed! (no exaggeration...). I immediately shut down after a couple of seconds or so and spent two days checking everything...cam chain tensioner, cam belt, cam timing, etc etc. and found nothing. After all this, when I started it up again, it was quiet. During the course of my diagnosis attempts, I spoke to a couple of respected independant Porsche specialists in the UK and both mentioned that sometimes the 944 hydraulic valve lifters leak oil when left standing for a while and can make such a noise. Anyway, that car ran perfectly for months afterwards and never gave the same problem before I sold it. My second experience was just a couple of weeks ago on my '91 S2. I had left the car at a paint shop while on vacation for 3 weeks. When I picked the car up, it made a similar noise, although not as bad as the previous car. On this occasion, based on necessity and previous experience (and taking a calculated risk!) I drove the car home carefully. The noise gradually subsided until it completely disappeared after about 10 minutes driving. I sold the car two days later (already arranged!!) and mentioned this to the buyer when he collected the car. I have since spoken to him a couple of times and the problem has not recurred.

My conclusion therefore is that it was indeed the hydraulic lifters "drying out" and needing sustained oil pressure to fill up again.

I hope this helps. However, just to be safe, some basic checks such as timing belt/cam timing, hydraulic chain tensioner (16v only) and turning the engine over by hand with plugs removed to feel for any internal contact of pistons and valves would be highly recommended, before running the car again.

cheers

Derek Holliday
Linköping, Sweden
'92 968 black/black

PrerYDoG

I had, what can only be described as everyone else has, a HORRIBLE noise out of my 88 T-S. It didn't happen after sitting awhile though. I drove to The Cinnamon Bear deli to pick up lunch, parked the car out front, went in and paid, brought the food out, started the car and SCRRRRRRR went this noise. I'm almost certain it was not the starter (heard 'em), and I'm almost positive it came out of the passenger side. I let off the key, turned it again, and started just fine.

I was parked on a very steep incline (pointing up), and thought this "may", for some unknown reason, caused the problem. I dunno.

philatnbn

It is a momentary thing that right as you turn it over. It would be in sync with the first firing. As soon as it happens, my reaction is to shutdown, so it only happens briefly (less than 1 or 2 secs). Then I start it up again right away and it starts a little hard, but nothing like the first start. This only happens every so often, like once or twice a month.
I suspect I have leaking fuel lines and vacuum lines on the car, which I will be looking into fixing. But can either of those make a noise like your engine is about to explode.
I had another 944 which I took to a dealer and they said the valve seals were leaking. It ran awful, making similar god-awful noise. Replacing fouled spark plugs would make it drivable. I did timing belt and valve seals and it has been running good since, except in extreme cold winters it seems to foul the plugs, change the plugs and it is ok again.