bruce7

I previously posted about replacing the SAI check valve and then cleaning out
the SAI air passages. But yesterday, one week later after doing the port clean-out,
the CEL returned with the P1411/P0410 codes.

I looked into what I could find about the SAI system and saw that there are
2 more valves, a cut-off valve and a shut-off valve connected by a vacuum line
that I needed to inspect to see if they were functioning correctly.

The cut-off valve sits directly above the check valve under the MAF sensor.
A short distance away to the left is the shut-off valve.

When I removed the air cleaner assembly and the MAF and looked back there
with a mirror, I found that the vacuum line between the two valves was missing.

I hiked up to the local NAPA store and picked up some Goodyear vacuum hose
in 5/32 I.D. for $0.75 per foot. I only needed about 3 inches though because the
connectors are very close together. Unfortunately, I wasn't able to get a good
photo back there showing the 2 barbs coming from the valves.

I also picked up a 2x3 inch inspection mirror that helped to show what was
back there. Very handy item to have.

I reset the codes and did a cold start. The pump could be heard to run for
2 minutes and then shut off.

Time will tell if this finally kills those dreaded SAI codes but I feel pretty confident
now that I've isolated the problem. Who knows how long that vacuum line
has gone missing. So all this time it never was blowing any air into the exhaust.

-bruce

eddie_993

Thanks for the continued update. I'm planning on starting all of this next month on mine and your info should come in handy.

JDHertz11

It just dawned on me but I installed an air injection bypass kit on a 2005 Toyota Tundra 4.7 V8 a few months ago. They're known to have air injection problems that throws CEL's resulting in reduced power, erratic automatic transmission behavior and failed emissions (due to CEL). I wonder if something similar can be done to the 993's? I can post a link to the $100 kit that I used if anyone is interested. I'm sure it would have to be reengineered but the thought process may translate?

nine9six

Bruce,
Nice work, well documented. Thanks for the update and info.

Garth S

Link please .... my Tundra would like to meet your Tundra ...

bruce7

Just a thought about how that vacuum line could have gone missing.

When I replaced the check valve, I was unaware that there was a vacuum
line back there. When the rubber hose was removed from the top of the
check valve, it was pushed up a couple of inches to give room to work and
at that point it may have dislodged from the change-over valve and dropped
down into the nether regions never to be seen again. Not sure it was there
to begin with, but this scenario could have happened easily.

Still looking for a good photo of that area to confirm the positioning of the
vacuum lines. Adrian Streather's book has some photos but they don't match
my 97 and I think some changes were made over the years.

-bruce

nine9six

I like your deductive reasoning...Sounds very plausible to me.
P.S. Bruce, could you post the photos of the area you are discussing, regardless of whether they match your 97? PLEASE!

JDHertz11

PM sent... no more hijack...

bruce7

The photos I was mentioning are in the book Porsche 993 : the Essential
Companion. I can get the book tomorrow and scan the pages and post.
It's a couple of pages in the book.

-bruce

bruce7

Here is something from the 996 forum on Renntech I found that explains how
it works. The 996 system is similar to the 993.

http://www.renntech.org/forums/topic...l-p0410-p1411/

-bruce

bruce7

The photo below is what I was looking for:

http://www.pcarworkshop.com/index.ph...101_-_0033.JPG

Looks like from this photo there is no straw connecting rubber elbows
together between the two valves. Just the single elbow connects the two
valves.

So the elbow simply popped off when I replaced the check valve most likely.

I'm going to update my previous DIY to include this note.

-bruce

bruce7

Hi, I scanned the two pages from the book and attached it as a pdf file.
In the photos you can see how the change-over valve is mounted differently
from my car. On my car a single rubber elbow connects the shut-off valve
and the change-over valve. On the car shown here, due to the distance,
2 elbows and a straw are used to make the connection.

P.S. I've update by DIY on changing the check valve and included some new
diagrams and a reference photo. See it here: https://rennlist.com/forums/993-foru...eck-valve.html

-bruce