RandalJ

I've been looking at a local 1997 993, and have found one with 50k miles that seems outwardly to be in really good shape, and drives well. I've had other 911s, but never a 993, so I've done a lot of searches here to learn what to look for.

But I do have a few questions regarding the plugged aux air issue, and a few other things.

Is the CEL/AI issue only tied to bad valve guides, so that if the better guides are installed, the issue won't come back ever? Or is there more to it than the valve guides?

If it is entirely valve guide related, then would the PPI have to include taking all of the valve covers off, and wiggling the valves side to side to determine whether problems are likely to develop? And is there enough working room to take off all four covers, and do this check with the engine in the car? And is it only the exhaust valve guides that we have to worry about?

I had earlier thought that compression and leak-down would tell me all I needed to know, but it sounds like, while those are vital tests to find other issues, they will not reveal worn valve guides. And that this rule broadly applies even to earlier, 80s Carreras.

For the one car I've looked at and driven, the independent dealer was up front about the car needing guides, and said that he was going to have it done at a reputable indy shop. One that I know of but have never used. He said that the valve guide issue was detected via some code readouts, maybe indirectly via emissions due to the plugged aux air ports. Is that one more way to know that guides are needed? He seems to think so. Anyway, he told me the cost would be $4000 to him, and was included in the $39k price. It sounded as though he was going to just do the minimal to address the guides, not a full top-end.

Another question I have, is if I were to buy this car, would it make sense for me to negotiate any other preventative work on the heads while the guides are being replaced? And I suppose other things could be found once it's opened up, so I don't know where I would be then...

The thing about the car that is attractive to me, in addition to the apparent condition, is that it had new clutch at 45k miles, has 17" stock wheels, has limited slip, and a folder with all service records.

By the way, I do think that the $39k asking is about $5k too high, even with everything sorted. But I'm guessing the dealer was not anticipating this expense...

Thanks.

NP993

Why was a clutch needed at 45K? That's 60-80K too early. And the previous owner didn't do the top end rebuild while the engine/gearbox was out?

If you really like the car, I would try to negotiate a lower price and then you can get the work done yourself, and take care of other issues that should be addressed while the engine is out -- seals, wires, rebuild the LSD, etc.

Dr. No

If you do a search for "SAI" or "valves" in this forum you will find a lot.

The SAI problem is not necessarily valve related. It has to do with some ports that clog, throw a code, and keep you from passing a smog test until you pay a lot of $$$ to clean them out. The car could be fine otherwise.

Valve condition relates more to oil consumption. A good 993 tech can tell from a compression/leakdown test and manual inspection whether there's a problem. Lots of people here have replaced the OEM parts with Jerry Woods guides that are supposed to be much more durable. If you look for posts by Steve Weiner, he's a guru. For $4k, that should address whatever's wrong with the top end. With 50k on the clock, you might go ahead and do the 60k service (plugs, etc) if a valve job is in the cards.

Spend some time with the search function - you will learn most everything you need to know.

RandalJ

Dr. No, I have done quite a few searches, and seen seen many varied opinions. Just trying to confirm the explanation the made most sense to me as to the source of the oil that would cause the carbon build-up at the SAI port in the combustion chamber - whether the port clogging was necessarily due to leaking valve guides. You say they are not necessarily, but I'm not sure of any other potential oil entry point into the combustion chamber that might cause carbon build-up other than the piston rings, and I don't recall rings being mentioned as possible culprits. I assume the clogging would progress from the combustion chamber outward, not the other way around.

But I will do the additional searches you recommend to see if there is anything I missed. Thanks.

NP993, good point. 45k on a clutch does seem way early. I'm not sure whether the top-end problem was known at that point. The first 44k miles were logged by 2004. So, only 8k miles since 2004, and the first code indication may have been since then. I forgot to mention that the CEL is not on.

RandalJ

I mis-spoke above. The SAI port terminates in the exhaust port, not in the combustion chamber itself. So, my question boils down to could you have perfect valve guides and still eventually get SAI clogging?

Dr. No

It's an air/oil cooled engine, so my understanding is "yes."

It has a lot more to do with short trips and low revs, that don't allow the engine to heat up and burn the stuff off - could be an issue for your short commute.

Steve Weiner-Rennsport Systems

The key to preventing SAI clogging issues from happening lies with two main items:

1) Better-than-OEM guides and proper fitment. In many cases, we've found that many engines left the factory with loose guides that were actually beyond the factory's own wear tolerance. These cars used too much oil right out of the gate and that caused premature SAI problems.

2) Opening the SAI ports in the heads for better airflow.

We do all of our heads here in-house and utilize our own guide material to eliminate this problem, once and for all. 993 heads get the SAI passages slightly enlarged as part of the rebuilding process and to date, we've not seen this issue recur with the engines that we've done, to date.

Hope this helps,

RandalJ

Yes, thank you.