Secondary air injection system issue

Batman10 · 10-25-2019, 08:41 PM

Hello, my Cayman 987.1 152K miles is giving me a CEL with codes P0491 and P0492, secondary air injection system insufficient flow.

I my AOS failed and was replaced a few weeks ago, and was running great since then, with a smooth idle. The weird thing I got this after the car was already warmed up.

I searched the forums for ways to fix but seen no real clear resolution but replacing eveything in that system one at a time, Also are there two air pumps(one for each side/bank) and how can they both be bad at same time,

I live in CA and cannot just reset the CEL, block off and disregard.

any more insight or experience would be greatly appreciated thanks

Batman10 · 10-27-2019, 03:14 PM

a clue into my issue,

today I noticed going uphill on canyon road the revs would surge a little every five seconds which was weird and new. but was fine crusing on level ground and when stopped...

Batman10 · 10-28-2019, 10:39 AM

under hard cornering the idle is fine,

I did the oil cap test while running and it there was no extreme suction so I am ruling out the AOS for now... but have heard some sad tales of new AOS installs that went south quickly,

my AOS failure was a bad one that got oil into intake, plugs, and probably cats so im thinking the oil must be in a air line or something

gizmofixer · 10-29-2019, 05:14 AM

i've had this same issue for awhile now on my 09.
if i baby it till fully warm, the code wont set.
problem could be the air pump, either of the checkvalves, a vacuum control solenoid or one of the many vacuum hoses.
if anyone has pics of what is what and where they are, please please please post them........
if you solve yours, please post the fix.

Jim & Kim 986 · 10-29-2019, 05:29 PM

2001 Boxster Base 158,000 mi Daily Driver

About a year ago I began to hear a whine coming from the engine compartment when starting the car. It doesn't last very long and it only seemed to occur after the car had been sitting overnight. We have the removable hardtop so accessing the engine compartment takes a few minutes.

After several attempts, I finally figured out where the noise is coming from. The noise seems to last longer now than when it first started. It now lasts two or three minutes and does it more frequently than just after the car has been sitting for a while.

I don't know what this pump does or when it is supposed to do it. I don't remember it ever happening before about one year ago and we've had the car for 12 years. I just serviced the car (oil change, filters, plugs, coils, etc). I did notice that the short hose from the top of the AOS to the intake/throttle body has a bad clamp and doesn't seal properly. It's on order.

Additional Info: We are experiencing hard starting after filling the tank and we are experiencing the whistling/howling sound coming from (I think) the front - fuel tank area OR filler tube area. I have already replaced the vent valve that rides on the filler tube and the OEM cap is only three years old. The AOS is two years old with about 14k miles. I don't know if these are contributing factors to the pump issue.

jlong · jlong's Garage

The high probability fix of the P0491 & P0492 error is to replace the secondary air valve. The valve is prone to fail over time (seize) and not allow the pump to flow air into the exhaust thus causing the P0491 and/or P0492. Use a Durametric or similar on your non-running car, actuate the air pump and check for flow out of the tail pipe. No flow? Blocked secondary air valve.

948 113 203 51 Secondary Air Valve

You must remove the right (pass) side intake and injectors to complete the job so also buy yourself new gaskets for the intake and the injectors for good measure.