Bigddiesel

Couldn't find any bad vacuum lines. Pump is noisy though. I disconnected the hose to the pump and there is a little bit of suction there. Pump makes a loud humming noise. Not sure how it should sound though

Bigddiesel

Is it possible the check valve is bad. And how can I test it

silverd2

Also check the pods for the intake manifold changeovers. I had one crack, losing vacuum, which produced SAI code ... all in the same vacuum circuit.

Bigddiesel

So I tested the pump out of the car to see if it's working. Put power to it and it fires right up. Relay and fuse are both good , but there is no power going to the pump. Checked it with a meter and the harness is not sending power to the pump. Any ideas

jfrahm

Check into testing the SAI system with VCDS:
VWVortex.com - How to test Secondary Air Injection pump with VAG?

Offhand I do not know if the SAI runs if the car is warmed up but restarted. If there is some logic like that you might have another problem where the ECU thinks the car is always warm (or you did not test it when cold and just started).

Bigddiesel

I don't have vcds as of yet. A mechanic told me it might be coolant temp sensor. Does that sound possible ? If it's not working properly it could be what u said , that the system thinks the car is warmed up

jfrahm

My 2001 A8 is warmed up, I will try to see if I can hear the SAI running when I restart it. If SAI only runs when the car is cool then yes I suppose the CTS could fool the system into thinking the car is never cold. However I think you'd also have some other codes, maybe really fat running when cold, etc.

jfrahm

I could not hear the SAI pump running with the car warmed up so I think the logic is to only run it when cold. Someone please correct me if I am wrong.

If you can find the specs for the CTS you could bodge it with a resistor to set the temp, or just replace it. On some years it is a common failure point. If you replace it I suggest wrapping a thread around the retaining clip and keeping track of both ends, I dropped one into the engine and it was a pain to fish it out. I think I bought a spare and dropped both of them. It was not my best day ever.

silverd2

The SAI only runs for 90 secs on cold start up ... will not run if engine is warm.

The CTS is a dual sensor in the same casing ... two independent sensors that can go bad one at a time. If the sensor sending signal to the ECM goes bad, reading high, hard starting should occur and the engine could sputter to a stop when cold (too lean). The other half the sensor sends signal (code 102 on the CC secret code readout) to the cluster processor, before it dumbs it down to an idiot gauge.

Bigddiesel

Thanks for the replies. The car is cold when I start it and the pumps not running. I guess I'll try to test relay again and check voltage coming from the harness that triggers the pump