I've had my car for a year now. When I bought it, it was consuming about a quart of oil per gas fill-up. Took the head off to see what was up, and saw that the No.2 cylinder was scored badly. Lots of $$$ later, rebuild, oversize pistons, etc, now I'm happy again. I think I've noticed others mention problems with their No.2 cylinder as well. Is this an inherent problem in 944's/951's? Poor oiling? Is there a remedy?

 

Here's my personal theory on bore scoring in the 944:

The 944 seems to have an ECU that gets flaky with age and the ignition part of it fails. So what happens is that the ignition starts to go, the car gets hard to start and requires a lot of cranking. While all this cranking is going on, the injectors are spraying. This gas is going into the combustion chamber where it soaks the cylinder wall near the intake valve. This takes the oil off the wall in this location, and the ring scores the bore because there's no oil there. I bet the scoring you are seeing is near the intake valve, am I right? I don't know why some cylinders are affected more than others except that valve deposits and injector spray pattern might play a role.

That's my theory anyway.

Bryan

 

When you're standing at the front of the car, facing the motor, are the intake valves on the far side, or near side of where you're standing? If they're on the far side, then you may be right, cause that's where the scores were. It just seems odd to me that No.2 would be any more problematic than the other cylinders. That's why I posted this topic, I'm trying to get an idea if it was in my imagination, or if No.2 is the most common cylinder to go bad. The PO had the ARC2 set pretty rich, so that may have been a factor. However, the car has always started up like a charm, so cylinder wash was not being caused during startup.

 

#2 is the achilles heal of all 944s. The route of the evil is poor lubrication (poor design). With that said, some people have decent luck keeping #2 (on the track) by filling the oil to max level or above. I myself actually lost #2 on the street. Hard lesson to learn.

 

I thought the #2 rod bearing was problematic because of poor oiling not the cylinder?

 

Standing at the front of the car facing the motor, the intake valves are on the far side of the cylinders.

It does seem odd that only one cylinder would be affected. Like I said, it's only a theory.

Another theory is that the car had contaminated oil at some point from the oil and coolant mixing via head gasket or oil cooler (on the normally aspirated cars). This created this mayonaisse looking stuff in the oil (emulsified oil) that could clog an oil channel. This would explain one cylinder being affected.

Bryan

 

Come to think of it...when I put my new turbo in, I inspected my stock K26-8. Some of the inlet impeller blades were slightly dinged. Obviously something foreign had gotten in their at some point. Perhaps it got lodged in the No.2 piston ring.

 

Erick - you're thinking of the rod bearing, not the cylinder walls/rings.

Scoring on #2 would make sense if you'd mangled your crank and bearing, though...

 

My 951 had all four cylinder bores horribly scored as well as the crank/#2 rod bearing being damaged. During the rebuild, we had the #2 and #3 rod bearing journals drilled through (cross-drilled the crank) as well as the re-bore and 1st oversize pistons to take care of the scoring.

In my case, the scoring was likely caused by a combination of (a) No air filter, or (b) An air filter that looked like it had several ounces of SAND in it AND (c) Horrible oil change regimen.

I'm happy to say that after pulling out the plugs and checking the bores with a lighted borescope, that all four look great after 10K miles since the rebuild.

Greg

 

I've taken apart a couple 951 motors with over 200k and the original bores were in great shape - both motors had 148-150 psi across all 4 cylinders. I've got a good block, pistons, and crank for sale if anyone is interested (150 psi across all four and no smoke).

From what I have seen top end damage does not seems to be a problem with these cars if they are maintained properly (or even somewhat properly).

With that said, #4 usually runs leaner than the other cylinders and this is usually where the headgasket will fail.

On the bottom end, once again #2 is the weak spot.

As for bore damage to #2 - that could be a really shaky rod bearing, bad air filter, or too much gas (among other things).

Whatever it is though its likely the previous owner abused the car pretty severly to leave that kind of damage.

Its amazing to hear of the amount of abused 951s that show up on this board. People please do a proper PPI including a madatory compression check before plunkering down your hard earned cash.

 

aka: I agree, i just started reading the rennlist boards about 3 weeks ago and through other reasearch I keep hearing about 951's with bad things happening. I'm lucky to have found a 951 with an excellent PO so my chances are high i'll have very few problems. I looked at a 89' 944s2 before and was amazed that the dealership said it was in "great shape" nothing wrong. When I test drove the car the first thing I noticed was the ! light was on. The next HUGE Warning was the fact that the shift know was replaced by an autozone fake carbon-fiber screw on job. In addition the clutch slipped, the rotors were in dire need to turning and a nice constant-with-speed grinding noise could be heard from the tranny. Unbelievable.

 

In case anyone cares, here's a pic of my scored cylinder.



Of note, I did have the car professionally inspected prior to purchase by Weissach in Vancouver. Apart from a few minor issues, they gave the car a decent rating. Compression and leak-down tests were within Porsche allowable limits. There seems to be a lot of fuzziness out there as to what people figure is an "acceptable" level of oil consumption in these cars. Now that the rebuild is complete, I barely go through any oil.