Steve Weiner-Rennsport Systems

For the most part, "Brother" Matt is correct.

This can be fixed properly with the right guides, correct fitment, and the enlargement of the passages in the heads and cam housings. This is SOP for ALL the 993 heads we do here in-house. FWIW, I'm happy to provide machine-shop services to anyone needing such things.

Software fixes are very complex due to the enormity of the OBD- II code and how it all interrelates. Some well-meaning software changes have unintended consequences and that creates problems for anyone scanning the car with the Hammer or PST-2. We won't do it anymore.

IMHO, the cars that suffer the least with these issues are ones that came from Porsche with tighter guide clearances than average and not driven much in heavy traffic with a lot of idling.

FYI, we did a set of 993 heads that came from another Rennlister's car with 3K,......3K! The exhaust valve-to-guide clearance was almost .025 with the valve stem wobbling sideways in the guide. Obviously, this one came from the factory with tolerances on the wide side and that would have resulted in premature SAI 1141 issues. All that one needed was our own guides; no other parts required.

Hope this clarifies things a bit.

zone5

Glenn,
Did you let a broad drive your car? My mechanic said that this problem only happens to 993s driven by women. I'm not joking either.

Allen

uhhh.........



Let me scroll down a bit to avoid the flack from the above.

I'd like feedback on a few questions/points: 1 - the ports being clogged, don't cause any mechanic harm...it simply presents an emissions issue (in the mind of the check engine circuit)...correct? 2 - Clogged ports are indicative of either worn valve guides...in which case you would also see "high" oil usage, or a bad SAI valve...correct? 3 - To say that all 993s will eventually have this "problem" is true enough. But, it's also true that all 993s (and any other machine with moving parts) will EVENTUALLY have all sorts of problems...they don't last forever. 4 - Unless you are in a state that requires emission testing...IMHO, it's not a big deal at all...other than dealing with the CEL.

g_murray

The SAI for OBD-ii 993's is certainly the ubiquitous Achille's heel.

Worn valve guides are the supreme culprit for worn valve guides allow 'deposits' to accummulate in the passages. The SAI check-valve, IMHO, gets a bad rap. There have been many cases of other renners yanking out their SAI check-valves, after *tens of thousands* of miles and finding nothing more than them looking a bit beat up and rusted, but still 'functioning'. Replacing the check-valve every 30K miles - as part of preventative maintenance - is good practice - but if your guides are completely worn-to-wobbly -- then no matter how many times you change the SAI-valve, you will STILL get a CEL due to 'blocked passages'.

FWIW, my own personal 'flags' and 'preventative maint.' for the SAI problem are:

i) Remove the engine under-tray.
i) Monitor the OBD-ii system (once a month) for 'pending codes'.
iii) Change the SAI check-valve every 30K miles.
iv) Let the engine/oil 'warm up' before you plant the right foot.
v) Monitor your oil consumption - and I mean monitor it - not just 'wing it'.

My $0.02,
Gerry

Glen

I would disagree with Matt, having owned 8 993's, 3 964's, 6 996 Cups and 1 997 Cup I have had"some" exposure to the various issues of each. I think if You will check Your valve guide wear after they are"worn out" by checking the valve movement(which will be of course outside of tolerance) then drive the crap out of the car for another year You will find it has not changed from that point much if any at all....just my experience, having had 3 993's with WAY over 100k each (all still had original clutches also ) that was my experience. I think they are getting old enough now to pass inspection in many states. Also most states dont have a AWD dyno so if You have a AWD its irrelevant as long as they pass the sniffer test. I think You will find they will all pass unless the inspection is kicked back by the CE light. But if You do the"fix" make sure to put RS cams in while You do...lol

Bull

+1

BTW, has anyone ever heard someone who sells the fix for the SAI problem say that you might not ever experience the problem????

Davies

I would tend to agree with that.
Unlike in earlier air cooled flat sixes (like the 3.2) the wear of 993 valve guides doesn't rapidly develop symptoms in the form of huge oil consumption and belching blue smoke. As Glen infers, a 993 with worn guides can go for a LONG time without significant symptoms - except for the breathtakingly irritating SAI CEL, which makes zero difference to performance but is merely - as I said earlier - the canary in the coalmine. It's just telling you something odd is going on in those SAI passages. It also is telling you you ain't gettin' no stinkin' emissions sticker.

How one "fixes" the CEL is up to the individual, but IMHO whatever small amount of crap that is getting past those guides and clogging up the SAI passages indicates a valve job is in the cards at SOME point in the future.

glenn993

Don't be an ***... Of course not! I had my mechanic run the standard check for any "chick miles" during the PPI - he found zero in the computer.

(sorry all, I couldn't resist the bait )

autobonrun

I think although material from valve guides could plug the ports, any carbon buildup could do the same thing. The problem is not limited to 993's and the BMW's issues appear to be all carbon buildup.

http://www.m5board.com/vbulletin/e39...t-attempt.html

http://www.m5board.com/vbulletin/e39...q-summary.html


I don't see this as a major problem unless you live in a state where it impacts emission testing. For those that do live in such a state, I feel the pain. Personally, I see three solutions:

1) Rebuild the heads so the path intended by the manufacturer is clear
2) Fool the electronics where it thinks more dilution air is available than there actually is
3) Bypass the SAI ports and pump air downstream through another path

Option 1 is expensive. Option 2 is questionable from a legal standpoint. Option 3 seems to make the most sense to me. Personally if I ever have this problem with my 993 or M5, I plan to install tubing from the air pump into the exhaust header upstream of the O2 sensors that detect the rich condition. To me the entire problem stems from placing a path through the heads. If the system wants air, give it air; but I don't see why that path needs to be through the heads. I could be wrong, but I think 1/2' stainless steel tubing could pass enough dilution air into the exhaust to satisfy the sensors.

H2NO

"Unlike in earlier air cooled flat sixes (like the 3.2) the wear of 993 valve guides doesn't rapidly develop symptoms in the form of huge oil consumption and belching blue smoke. As Glen infers, a 993 with worn guides can go for a LONG time without significant symptoms . . . "

Really? This is news to me. I was under the assumption that so long as my car didn't consume too much oil and didn't smoke my valve guides were probably okay.

fbfisher

This is a depressing thread. No surprise that Porsche dodged the issue. If I ever buy another 993, I'll buy a '95 so that I don't have to worry about this issue. CA cares about such things and the anxiety associated with this problem (and the cost to temporarily fix) sucks, it's like a ticking time bomb waiting to go off, it probably will, you just don't know when.

uncle buck

We have a winner!

'95's are the fastest anyway...

Flying Finn

True but bad valve guides are basically all Porsches problems and it only becomes a real problem much, much later than when the clogged ports is a problem for OBD-2 cars (remember, OBD-1 cars don't suffer from this).

Correct, you might have clogged ports, say at 60k but your valve guides need replacing, say at 200k.

I thought about the same thing! Famous last words...

fetus

That might be true for most Women but you haven't seen the way my wife drives. She was 19 when I met her and I needed a car to abuse for sales calls so I took her honda and made her drive my home made 914-6 to and from work. The carbs were jetted wrong so i told her to never let the revs get below 4k or it will load up and die. Sad to say she now drives every car that way. Never below 4k and always to red line. She is now a Soccer mom and drives our Toyota Sequoia that way as well as my Porsches.