tam993

I tend to agree with Loren. had a problem with SAI at around 70K. I cleaned out the passages.
the check valve was rusted open half way which I suspect help the issue. the car still uses about 1/2qt
of oil in ~2k miles. I looked at the exhaust valves 3 of the 6 were clean. To pull an engine with a factory build and have the top end done would have been a complete and total waste of money.
the compression was in spec. so was oil consumption.
haven't seen that SAI issue since, it's been 10k miles. total cost less than $200.00

g_murray

Hi,
Google it and you'll 'see'.
Oils HIGH in phosphor tend to be for motorbikes - Amsoil comes to mind.
Those for cars *nowadays* tend to be medium-to-low in phosphor because of the cat-plugging problem. However, up until a couple of years ago they were 'reasonably high' in phosphor -- so those of you who 'stashed' your oils may still have some in your garage (lucky you!).
G.

trojanman

I must say that my specific experience doesn't support this theory. My car was chewing through a quart every 500 miles before my rebuild, and now only gets maybe half a quart between oil changes (5k miles). My primary use of the vehicle is an 18-mile round trip to work every day, mixed driving with freeway and stop-and-go.

I'd be worried if my car were plowing through a quart of oil every 1,000 miles or less, regardless of how it was driven.

TCallas

I think everyone is going too far with this Valve guide issue. When your check engine light (CEL) comes on, it does not mean it's automatically worn valve guides. You have to go to a shop that utilizes the Porsche Systems Tester 2 (PST-2) and the most important thing is that they know how to use it. I cannot tell you how many shops that don't really know how to use their PST-2 completely. When you get a check engine light, you determine if you have a secondary air injection (SAI) problem by checking the pattern of the Oxygen sensors mainly before the Catalytic converters. Now, here's the key. You activate the Smog pump by bypassing it electronically. You manually turn it on while observing the Oxygen sensors to see if they are getting the oxygen from the SAI ports. If they do not respond and the complete system is working properly including the check and control valves (the check valves rust and stop working and the electronic control valve usually gets disconnected), at that point you most likely have clogged SAI ports. The next thing to do is remove the left SAI pipe on the top of the cam tower and try to blow compressed air into the left cam tower. The reason I have chosen the left side of the engine is because we have seen that the left side (Cyl's 1-3) seems to clog more often. If you cannot blow any air into the SAI port then the tests are showing more so of a clogged SAI port issue. Now, the last and confirming test is to remove the left lower valve cover, rocker arms and shafts including valve springs and check the valves for wear. This usually shows the suspect worn valve guides. You can even measure the valve guide wear. You can also remove the left heat exchanger and look directly at the SAI ports and see if they are clogged with oil burnt carbon. It's that simple, no hidden maybes or possiblities period. I have had so many shops contact me in regards on what to do and how they should handle an SAI or PST-2 issue I cannot tell you.

SwayBar

Excellent post.

Droops83

Good discussion here. The posts by Tcallas and Steve @ Rennsport mirror the experiences at my shop closely (great posts about procedure for checking if ports are clogged Tcallas and about the valve guides Steve!). The head tech at my shop always told me that the valve guides Porsche used for the 993s (and 3.2s/964s) are too soft for the type of driving most Americans do, ie short trips, lots of cold starts w/out warming up the car, etc. We are in Santa Barbara, where everything is like 5 mins away so we see this A LOT! The customers who baby their cars and keep them in perfect shape, but hardly ever drive them and are 15 years old w/ 30k miles of short trips on them are shocked to learn that they need a top-end rebuild. The key is to warm the cars up properly, and drive them like they were designed to be driven. This is NOT to say rev the crap out of em and rag em out, but give her a little bit of poke!

It is true that the clogged SAI issue seems to be caused by the valve guides most of the time. Cleaning out the ports alone is basically a band-aid, but I suppose if you just got it done every once in a while and your oil consumption isn't bad you'd be OK. As loren mentioned, other german cars have this issue. We also work on BMWs, and just did a valve job on a '00 E39 M5. the SAI ports were clogged solid, and in turn one of the #5 exhaust valves burned up. This guy seemed to do mostly puttering-around-town type driving too, but I am not sure how much the valve guides themselves contributed, but I wouldn't be surprised if they did . . . .

So the moral of the story is, warm up your car properly, change your oil, monitor your oil consumption, and have fun!

---

Chris Andropoulos
Schneider Autohaus
Santa Barbara, CA

Father of 3

When oil consumption comes up, nobody ever talks about rings as a possible culprit. If rings are worn or cylinder wall scored could that also be a source of oil consumption? Would that necessarily mean huge plumes of smoke out of the tail pipe or would oil usage by means of worn guides and worn rings produce the same symptoms?

Davies

So a bad pre-cat O2 sensor reading on the PS-2 can actually mean clogged SAI ports? I thought the PS-2 was able to differentiate and inform of Secondary air issues specifically. I just got a bad O2 sensor reading (before cat) and assumed it meant, well, a bad O2 sensor...

Lorenfb

"So a bad pre-cat O2 sensor reading on the PS-2 can actually mean clogged SAI ports? "

Correct!!!!!!!! That's the purpose of the test & how it's done, i.e. by using the front
O2 sensors to check the O2 voltage value when the air pump runs.

"I thought the PS-2 was able to differentiate and inform of Secondary air issues specifically."

No, you have to understand the data which most can't. So having any form of a
tester is useless for many. A tester is ONLY a data reporter! You can use the
PST2 to run a specfic test (Short Test) on the SAI system but it's only a PASS/FAIL
with an O2 voltage indication. It won't tell you the exact problem, e.g. air pump,
check valve, bad passages, O2 sensor, & etc.

"I just got a bad O2 sensor reading (before cat) and assumed it meant, well, a bad O2 sensor..."

Could well be, but more analysis is needed, e.g. could be the heater element
voltage source, wiring harness, intake air leak, MAF sensor (affects both sides) & etc.

Note: The SAI system is only checked during cold start mode,
i.e. no air flow or a bad (slow response) O2 sensor can cause
the SAI CEL (410/411).

Bottom line: It's very rare for most techs to really understand the OBDII system,
which results in very unnecessary & costly repairs on 993s, e.g. valve jobs!

TCallas

Well, unusually enough, this time I totally agree with Loren. Great answer and hope this helps. This is hard enough for the techs to differentiate. I have tried to school many techs on the PST-2 and how the systems work. I feel bad for the lay person trying to get it. Hang in there guys and try to get as much information as possible so hopefully a mechanic will not get the best of you.

Bull

Bad O2 sensor readings is what caused me to find a contaminated MAF sensor on my car. Until I found the cause, MANY were telling me that I had clogged SAI ports, would need to spend thousands, should never have purchased a '96 and '97 "OBD II car", etc. $380 later, no probs for several years.

bugnbox

Very interesting read but its getting a little too technical for my little brain...but that might just be me.

I just had a PPI done on a 96 C2 Tip that Im looking at buying. The tech did a leakdown test and the numbers came up between 2 and 6% which according to him is totally acceptable (is this right?) Im not sure what he oil consumption is, the car was about two quarts low but the mechanic sounded a little apologetic thinking that when he last did a service, perhaps they didnt fill it up all the way. The car has 106K on it so it's no virgin, but I think it has been treated pretty well looking at it closely...its pretty dang clean. The price is right too...plenty cheap, well under priced so I think Im going to go for it.

One question...does synthetic oil make a difference in all this?

TCallas

This is all very easy to understand and it's our fault for not explaining it better to you. Hey, just make sure this car has no clogged SAI ports or\has not been in a bad accident or be prepared to spend quite a bit of money on it to repair it if it does/has. I hope you utilized a good well known Porsche repair shop to do the PPI. It can save you thousands in the future, possibly near future. Please note, an engine leak down and compression test will not necessarily show worn valve guides. This is a key note. Don't jump and make a quick decision based on emotion. There are a lot of these cars out there.

bugnbox

The car hasnt been in any accidents...so Im good there, its all original paint and such, clean carfax, etc. I will have the mechanic check the PPI ports (is this a pretty simple thing?).

Im wildly thankful for all the advice. Its an emotional buy but I cant imagine it not being. The key factor to me right now is the financial parts of things. Ive watched the market on these cars carefully for the past 5 or 6 years and have been waiting for them to come down to my level. Right now I can swing this particular car easily, pay cash for it and start playing now. I dont much want to wait much longer...it's been 10 years, and any of the other 993's that I have seen for sale are at least $5000-7000 higher in price...they may have less miles, but as I have read in the posts, lower mileage doesnt seem to be a guarantee that the problems wont be there.

Im trying to be cautious, ask all the questions, give it deep thought and lots of research. Im buying it knowing full well that there could be expensive repairs in the future...but buying ANY Porsche would be the same regardless of miles or model...it's just the way it is...if you wanna play you gotta pay.

Whenever I get all freaky thinking about it, I pull up my life motto in general... If you live your life in fear, you live dying...if you live your life by joy, you die living. And this car is most certainly a joyful thing...

Davies

Lorenfb and TCallas,
THAT is excellent, eye opening info. I owe you guys a beer. Thanks!