When I short out A and B to get my trouble codes I get a strange noise from the injectors. Well, some where around the injectors or plenum. It also does this after I start the car, turn the key off it will make the same noise for about 3 to 4 seconds. When in diagnostic mode it does it the entire time the key is on. It sounds like a hollow deep knock but fast like a Tattoo gun fast. It's very strange to say the least and I started noticing it doing this after I installed my Bosch III's I just got in. That's the ONLY thing I have done different to the car is install new injectors. If I go out and turn the key off and on without starting it, I don't get this noise. I have to let it actually fire and shut it off to get the tapping sound. Or put it in diagnostic mode and it will do it the entire time the key is turned on.

It's hard to describe the sound of the knock but it isn't injector ping type sound, this is more like putting a piece of plastic in a house hold fan and letting the plastic blade hit what ever you stuck in there. It's that type of hollow sound. Unless the Bosch 3's make a different injector pulse ping than stock?

Any help figuring out what is doing this is appreciated.

 

your iac is moving

 

Is this normal though? I can't honestly say I have ever heard this before when checking codes or shutting off engine. So I am curious if I messed something up when I put the throttle body back on.

 

go put you hand on the iac/housing and see if this is it. It is normal when in diagnostic mode koeo the iac is commanded in.

 

Yea, it's definitely the IAC. Since you pointed me to the source I put my hand on it when in diagnostic mode and moving the harness around changed the noise and tone. So this is what's causing the noise and if it's normal in diagnostic mode then nothing to worry about then.

The only other time I can hear it is when I shut the car off. it will do it for about 4 seconds or so. I verified it as well by placing my hand on it and shutting the car off and it's the culprit.