SAI CEL FAQ

[Don Plumley]

Here's a quick FAQ on the SAI CEL issue for 96+ 993's:


Q: What is SAI?
A: Secondary Air Injection

Q: What does it do?
A: In 993's, the SAI system is a small electric pump which blows air through external tubes and internal passages in the heads into the exhaust ports during startup to reduce emissions. It operates for 1-2 min on cold starts and does not affect the performance of the engine except as regards cold start emissions.

Q: What is the issue with the SAI system?
A: The passages have become problematic for some owners - becoming internally clogged or externally leaky (transfer pipes rust, check valve malfunction) which triggers a CEL.

Q: What is a CEL?
A: Check Engine Light. Also known as a MIL (Malfunction Indicator Lamp).

Q: Why is this important?
A: If you live in a smog testing state, this CEL is an immediate fail -- which can have expensive consequences.

Q: Are all CEL's SAI related?
A: No. They can be for a variety of things.

Q: Do all SAI CEL codes mean the passages are clogged?
A: No. Many times, the CEL is about the check valve failing or other non-passage related problem. Some unscrupulous mechanics will recommend a full top end rebuild when a much simpler problem could have been fixed.

Q: What causes the SAI passages to become clogged?
A: The most common is a failed check valve or carbon from the exhaust blocking the small passages in the head. The problem is acerbated by valve guide wear. Excessive engine heat, extended stop and go traffic, and lack of high RPM driving also appear to be factors.

Q: If I don't live in a smog state, or don't care, is this a big deal?
A: No. The clogged passages do not impact anything other than smog testing.

Q: Do 1995 993's have this problem?
A: Some do. But their OBDI computer does not log it. So no issue with the smog folks. In most localities only '96 up OBD2 cars are subject to scrutiny of this smog system.

Q: Is this a problem for non-US cars?
A: No. They do not exist on RoW spec normally aspirated engines. Go thank your Senator.

Q: How do you fix it?
A: The definitive fix is a top end rebuild (spendy). Some have success with a flushing procedure forcing fluid/chemicals down the passages under pressure. Some people have luck resetting the code prior to testing.

Q: How can you prevent it?
A: Replace the check valve as a preventative at 30K intervals. Avoid extended stop and go traffic. Drive the car hard, bringing the engine to redline. It sounds good and makes your heart pump faster as well.

Q: Will it happen to all 993's?
A: Unknown. It will probably happen to a reasonable percentage of them, but for every clogged SAI 993 you hear about, there may be 5 to 10 that you don't.

edit: Team effort - Bill V took my few comments and added the technical meat.

[AFJuvat]

I've made this as a sticky for all to read.

Thanks Don!

[Lorenfb]

Read here:

www.systemsc.com/pictures.htm

[Don Plumley]

A member asked:

I live in a Fl where we have no vehicle inspections. I was wondering if there is a way to disconnect the Secondary Air Injection pump and will that prevent the clogging from ever occurring?

As far as I understand, disconnecting the pump will probably have no real impact upon clogging or not, except probably accelerating it. It is primarily the failure of the check valve (downstream from the pump) that causes clogging.

Since there are no smog inspections, then you have zero worries. If it clogged, it would be no big deal for you. However, if you are concerned about SAI clogging on a sale later to a smog state, I'd replace the check valve every 30K miles. And drive the car to the redline every now and then -- plus it's fun!

I sold a 98 C2S and the buyer was extremely worried about the SAI issue. He was skeptical of all 993s and wanted to know if my car still had the check engine light connected because some people disconnect the bulb once the issue presents itself. The car never had the SAI issue or check engine light come on however after reading your FAQs it made me wonder if the pump was disconnected before a potentially afflicted car indicated the CEL would the CEL ever initiate with the pump disconnected? I understand the pump isn't the issue but it is what's getting the air flowing and moving the clogging substance.

If the pump was not working/disconnected, that cause a CEL. Also, disconnecting the bulb would only hide any CEL's from a buyer not astute enough to have a PPI or use an OBD II reader.

Don

[Lorenfb]

"It is primarily the failure of the check valve (downstream from the pump) that causes clogging."

No, it's not. It's the design of the air passages AND the excessive oil
burning (valve guides) that cause the problem.

[Rick Lee]

A lot of the Rennlist guys have had success with the flush method. I think it runs about $200 in parts and tools. Some guys have built a pretty cool template tool for blocking off the exhaust ports on the heads (heat x'ers removed) so you can blast each cyl. individually with compressed air, while the other five are blocked. I get about 1800-2000 miles to a quart of Mobil 1 and have 56k on the car. So I'm not too worried. But I will definitely do the flush method before I tear into the top end. For you LA guys, I think Hergesheimer pioneered this fix and they do a lot of them. Not sure too many other Porsche shops would know about it.

[downtempo]

This is all very helpful info for a guy that's trying to buy a 993.

I've been looking for ages and now that I found one I like that's reasonably priced, I'm worried about SAI/OBD2 issues since I live in CA.

The car I'm checking out is a '97 with 70k miles which from what I hear is about when this issue starts raising it's head.

I'm curious if anyone has insight into how often this problem is a result of the valve guides vs just the check valve or some other problem. I'd hate to buy the car only to learn I need to drop another $8k+ into a top end rebuild.

At my PPI, the tech said the car is showing a "Secondary Air Fault at Bank 2." That sounds like it's only reading the fault from one side of the engine...? I wonder is there 1 check valve or 2? If only one then it would seem strange to only pick up the fault on one side....

I'd really appreciate any insight you guys may have....

Thanks!

[CAAB]

Forgive the question but what does OBD mean?

[Paul Crowther]

On board diagnostics, I believe.

Paul

[rcwaldo]

I do these SAI circuit flushes and cleanouts from time to time with very good success. Of the cars I see, most are 1996 models with primarily RHS SAI port blockages, cylinders #4 and #5. I have also noticed more 1996 models with exhaust valve guide wear. Is there a pattern, I am not certain, just an observation.

Here is a typical 50K mile check valve -- notice the rusted and degraded hose barb. Inside doesnt look any better. These are about $60 from the dealer.


Upon flusing I notice the LHS (cyl 1-3) get a bulk of the airflow. I can only conclude this is a result of the nature plumbing layout. Both sides combined, cylinders #3 and #6 receive the most pressure. Initially, I use a modified SAI check valve with a welded air hose quick disconnect.


Tapered rubber plugs are used to isolate cylinders that are blocked the most. Of course, these plugs have to be retained by way of a strap.


I feed a twisted .034" stainless safety wire up into the SAI port, just behind the exhaust guide in efforts to brake loose carbon deposits. But one can only get so far. Squirting foaming engine degreaser and Techron into the SAI ports [with the little red straw that is found on many types of aerosol containers] can help. I use a modified air nozzle that reaches up and around the exhaust valve guide and into the SAI port.


*Note; one must ensure the exhaust valve is closed to prevent solvents from entering the cylinder -- even then, pull the lower plugs and spin the engine before starting, after reassembly.

Once all ports are flowing freely, pouring -some- Techron into the SAI manifold, where the check valve was removed (near the #6 cylinder), and chasing with some airpressure (~80 psi) helps verify the ports are open.

http://www.youtube.com/watch?v=6sQYi3iCMw4

[Don Plumley]

Isn't capitalism great:

Porsche 993 SAI Bypass

[Rick Lee]

Does that thing work?

[Deadeye]

Has anyone had any first hand experience with this tool from Turbowerx? It sounds too good to be true.

[Jascha]

Originally Posted by rcwaldo

...

Once all ports are flowing freely, pouring -some- Techron into the SAI manifold, where the check valve was removed (near the #6 cylinder), and chasing with some airpressure (~80 psi) helps verify the ports are open.

Thank you for posting your perfected approach…

I have one caveat to add: I would not recommend to the uninitiated to use such high pressure. The risk is that you will blow out the thin-walled plugs (x2) on the manifold body. These are plain steel type, they tend to rust and will surely rapture under extreme pressure and solvent use (see image below)


use…

[TRE Cup]

TurboWerx OSD+ Tool

This product is on indefinite hold, pending possible cancellation. No further information is available at this time.

[ship4u]

Hi Don,
Thanks for the great information. I have a 95 with 39K miles on the clock. What are the consequences, if any, if my SAI passages become clogged? Will the performance of the engine be affected? Will there be issues when starting the engine? Will adjustments need to be made when tuning the engine in order to compensate for the clogged passages?
Thanks!
Don

[TRE Cup]

uh.... 95's did not have SAI passages

[ship4u]

Originally Posted by TRE Cup

uh.... 95's did not have SAI passages

Hmmm, my understanding is that the 1995 993's have the SAI as does the later years. But the 95 has OBDI and not the OBDII, so the CEL is not an issue.

Regards,
Don

[TRE Cup]

ok- my bad
you won't suffer any performance issues and there is no tuning to compensate.

[Don Plumley]

Originally Posted by ship4u

Hi Don,
Thanks for the great information. I have a 95 with 39K miles on the clock. What are the consequences, if any, if my SAI passages become clogged? Will the performance of the engine be affected? Will there be issues when starting the engine? Will adjustments need to be made when tuning the engine in order to compensate for the clogged passages?
Thanks!
Don

There are no issues with clogged ports on OBD-I cars. That's what makes this particularly frustrating for OBD-II (96+) owners.