There are some useful old Threads here for diagnosis and repair of the Secondary Air system. For a system that only runs for a few seconds ,it sure gives a lot of headaches !
http://986forum.com/forums/performance-technical-chat/51166-secondary-air-injection-veterans-needed-post597891.html#post597891
One of the many complications is that the diaphragms and valves may deteriorate slowly so the problem is hard to find/replicate in the car. Not to mention most of the system is buried and adjacent to brittle AOS parts!
The other is that if you fail Smog you may be unable to register your car and you may end up at the Referee.
I am still struggling with the "Not Ready" but no codes problem years later and came up with a diagnostic tool /hack to help pinpoint the problem.
That problem is that everything I can check has been verified or replaced but still "Not Ready". Reassembling everything without having found the cause is a lot of tedious work.
Previous hacks/emulators have not always been successful. I encourage thoughtful criticism of my hack below. I'm NOT selling anything.It is for diagnosis only for the benefit of 986 Forum members only..
My hack is just an accessible,reversible,manual over-ride. Can you improve on it ?
"Before you refit the Intake Manifold you can't test the whole SAI system.So you just refit and pray ? Maybe there's an alternative.
Here's the only way I know of testing the S.A.I for flow/vacuum with the engine running at cold start. Why is this significant ? - because suppose all the components tested 'good' but there is a weird electrical problem supplying voltage to the Change Over Valve at start-up . If so,the SAI pump may run correctly ,any vacuum test will be normal but you'll still have a SAI code because the Shut Off valve 'sees ' no vacuum and fails to open .
To allow testing for vacuum before the ShutOff Valve/after the Change Over Valve with the engine running, add 1, 12" long vacuum hose via a brass Tee.
One Tee anywhere before and a second Tee after the Change Over Valve(before you refit the Intake Manifold!!). Yes, fit one Tee on the output and one on the input side of the Change Over Valve. Run the new bypass hose UP between the runners of the Intake Manifold. When you don't need it just plug it. Now you have a hose end ON TOP of the Intake to connect a vacuum pump or to a manometer(or your finger tip) to measure vacuum and test the system.
The Manometer should show strong vacuum
at cold-start only, on the output side of the Change Over Valve.. Vacuum should collapse when the SAI pump stops running(60-90 seconds). If there is no/insufficient vacuum, the Shut Off Valve will not open to allow SAI air flow from the pump to enter the exhaust stream.The input side of the Change Over Valve should always show vacuum with the engine idling.
HERE'S HOW TO USE THE new vacuum HOSE to hack-fix a silent problem .
Temporarily connect the hose to an existing vacuum line .Add an extra Change Over Valve on top of the Manifold and fit a discrete , MOM switch .Connect the Hack-fix vac line to the output from the extra Changeover valve. That way you can manually turn on the SAI vacuum and Secondary Air flow for 60 seconds at start up for 3-4 times to prepare for the Smog Test.Once you've passed Smog, ignore the MOM switch and use the next 2 years to fix the problem correctly. But please let us know how /if you fixed the problem?
Check your repair by monitoring the sine/flat wave for the O2 sensor voltage at cold startup."
A Changeover Valve for my 2001 is $60 Pierburg 7PP906270 or 7.22280020. Recommend Pelican to verify your selection/fitment.
Brass Tees and silicone tube -online ,inexpensive.
[B]
There is one BIG flaw in this hack.[B]. The old parts "tested good". Good compared to new ? or just seemed to work? I suggest the Shut Off Valve #99711324990 $100, should be replaced regardless of any positive tests. If you test it up to 10"Hg you will see the piston move and you can blow through it. BUT if you clean out the carbon and swill some PB Blaster around the cylinder walls and top land of the piston &
retest - it moves more ! So maybe it was
restricting air flow from the SAI pump ? You need very bright light and almost dental tools to do this cleaning.It is so difficult to reach this part that imho ,don't even test it. Replace it.
The Change Over Valve is more binary but there have been superseded part numbers so I'll change that anyway. Yes my original works but the little foam air filter underneath the black end cap was deteriorating. Consider relocating the new replacement it to a more accessible and cooler location per my Hack above. Then if you have problems it is easier to diagnose/test/replace. The new version is lighter weight(more plastic/less metal??) so may be more vulnerable to engine heat?
Hope this helps you and others who follow.
Linear Mode
