Posting this for a fiend. He just bought a 99 Vette and is going through it all. He has a knocking or tapping noise in drivers side right after the air pump shuts off. We started, stopped the engine many times to conclude this. only starts once air pump shuts down .If you raise the rpms it gets quieter. Its racking his brain cause he just gave $20,000 cash for this car. The only code he has is secondary air pump fault or something like that. Thanks in advance!

 

Might be a bad AIR check valve.

 

Like Al said, it's probably a failed check valve. We could help you more if you provided the actual DTC... So this knocking noise is NOT present with the pump running?

$20K for a 99 Vette? He got ripped off, badly.

 

Yea happens only after AIR pump shuts off, not while its on. Well he traded two vehicles worth over 25000 for both but only had 8000 in them. He wanted a Vette bad. lol. They were asking $20000 for the Vette. Im trying to get the actual code from him.

 

"Secondary air injection system malfunction" is what he says.

 

Id bring the car back and get your money. like said above 20k for a 99 c5 is insane, even with low miles. So unless them car is built out the azz you did get ripped. Trying to fix anything will give the previous owner a reason to say the problems were caused by you. I wouldnt touch it, go knock on the previous owners door and ask for a 20k check.

 

Let's try this again. We need the actual DTC, not the description. It will look like this "Pxxxx", with the 4 x's being numbers. Something like P1415, P1416, etc.

 

Maybe an an exhaust leak where the air tube bolts to the header. You won't hear it when the air is blowing into the exhaust, but once it is off you hear the tick of the leak. You can buy gaskets for those at the GM dealer for a dollar or so, or get some block off plates from a vendor.

-Geoff

 

Finally got him to give me the code: P0410

 

And im quite aware what a DTC looks like considering i have been wrenching on cars for over 20 years and have owned lt1s since 95.

 

P1410 means the PCM isn't seeing the required <100mV output from the O2s with the AIR pump commanded on.

Jump the relay for the AIR pump and check output by disconnecting one of the large hoses to the check valve. Do you have airflow? If not, check for vacuum on the AIR pump shut off valve. If vacuum is not present, check the vacuum line under the battery tray - most likely it is broken from leaking battery. Let me know how that goes and we can continue the diagnosis if necessary.

As far as the noise... It is coming from the engine itself right? Are you sure it's not the typical piston slap?

 

Possible piston slap. I told him it might be that. hes going to delete the EGR and AIR anyway and go from there. Thanks everyone!