redfrog

Hello comrades,

My CEL came on recently with code PO410. I know this means insufficient air flow cylinders 1-3. Before launching into air passageway cleaning, I was considering replacing the check valve. This car has 48,000 miles, I am the third owner and I don't believe the check valve has been replaced. The CEL came on after 9 miles of driving on a 65 degree day. I thought this error code would present sooner after startup, while the air pump is operating, which would suggest maybe that the check valve is not the cause.

Any thoughts or recommendations related to check valve and code PO410 appreciated. I have read the lengthy SAI recap and do not see any discussion about why the check valve might or might not be related to an error code in the conditions I describe - 9 miles after startup.

Thanks all

pp000830

Hi Red Frog,
Yes, replace it first, clear the codes and see if it comes back.
If original you may need to use the heroic removal method I used.
See "Air Injector Pump Check (SAI) Valve Replacement" on the 2nd half of this page:
https://993servicerepair.blogspot.co...horror-of.html
Andy

redfrog

Hi Andy,

Thanks for this. I spent some time browsing your blog, lots of great stuff there.

David

redfrog

Andy,

I replaced the check valve. Was not too hard, I bought the crow foot from Pelican. Drove the car about 300 miles over the last year, no CEL. Thought I was done. Today after driving ten miles the CEL came on and the code is the same, PO410. I thought the "normal" presentation of 410 was very soon after start up. Today, and the last time it came on the car was fully warmed up. Reason I m thinking this is odd is because if I understand correctly, the SAi pump only runs for a few minutes upon startup. Any suggestions on what next?

Thanks

GJSPIN

How's your oil consumption been? I ask because the valve guides on these are notorious for wearing prematurely.

PRSWILL

There is a SMALL vacuum line next to the check valve that is VERY EASY to miss or disconnect. Make sure it's plugged in properly. I missed it after my SAI valve clean-out and the Engine light comes on- plugged it in and it was gone. It's only about 2 inches long and elbowed- There's probably pics out here- but it's right next to the SAI valve.

pp000830

Here is how I would proceed.
--If you are using Durametric make sure you are using the latest software from their site. If not uninstall what you have and reinstall the latest version, clear, and rerun the code. Durametric had a known issue related to oxygen sensor derived codes on earlier software revisions and also with their old cable and software.

Then detach the hose to the new check valve and with the engine dead cold have a friend start the car when you are behind it. If the air pump is working and the vacuum-controlled valve attached to it is opening you will hear what sounds like a jet engine sound for just a few seconds coming from the hose and strong air movement which is the pump running. It should be reasonably loud but if you want to make sure you hear it use a short length of hose as a hearing aid directed into the area where the hose is detached. This test can only be done once at an initial cold start or again much later from a dead cold engine. if your OBDC reader features actuations one can turn the pump on manually as well.

If the pump & valve check out then buy the two oxygen sensors for that side of the car, bank 1-3 is the left side of the car, and replace them. Many cars have older sensors that can contribute to an erroneous SAI CEL. If purchased in the Bosch branded box they are not expensive and are easy to replace.
Here is a page that describes how to replace them in your driveway:
https://993servicerepair.blogspot.co...anagement.html

-With new oxygen sensors, a new check valve and verification that the pump and vacuum control valve is working the next step is to clear the code and see if it returns.

If it returns you probably need to have the ports cleaned.
Andy

m32

Check out my journey to figure out my SAI CEL code. Hope it helps

https://rennlist.com/forums/993-foru...cel-codes.html

Edwin

redfrog

Hi All,

Thanks for the responses guys. I checked that the SAI air pump is working well per procedure above, robust air flow, rushing air sound, ran for two minutes. I checked that all the hoses around the check valve are in good condition and connected. No signs of corroded plugs. Oil consumption is not high,

So its off to the O2 sensors. Will do both upstream and down with Bosch. Neither Pelican nor RockAuto differentiate between left and right. Is there a difference, like the wires are different lengths?

This car has 49,xxx miles and of course is 26 years old but everything I dig into reveals good condition, good maintenance, etc. Really nothing out of whack, so far!

Andy if you could opine on the left right question would be much appreciated.

Thanks

David