Loud pop, now high idle

[1slow95]

I just turned my key on and heard a loud pop from under the hood. The car didn't want to start at first and took about 6 or 7 rolls more than normal to fire, then it was idling at 1300-1400 rpm instead of the normal 900-1000. I was able to move it into the garage without touching the throttle.

I just got home from a short cruise and shut the car off while I moved my bike out of the garage. This happened when I went to start it back up a few minutes later.

I had just changed the IAC response time from 303ms to 250ms in the computer. That's the only thing I changed other than the tip in/throttle accel pump settings. Did I blow up the IAC??? TPS is working like normal, and the MAP sensor looked right so I don't think it's a vacuum leak...

 

[HISSIN50]

Mike, any codes?

Did the MAF pop off the inlet tubing? Any vac lines blow off or pop off? It could have just been some weird backfire and now the high idle is from a vac leak...............

 

[1slow95]

AEM computer so no codes. No MAF either. The car wasn't even running when it happened. My first thought was a vacuum line popped off but they were all still on there. The car was still pulling 17in hg vacuum idling at 1400 so I figured it's not a vacuum leak...

If I can find my old IAC I'll try it tonight and see what happens.

 

[BlackVert]

you probably blew a vacuum hose with a small backfire.

 

[1slow95]

Well now I'm thoroughly confused. Swapped IAC's, same problem. Unplugged the IAC, idles fine at 850-900. I did have the IAC set at 50% for an idle of 950ish, but now I have to set it down to about 15% for it to idle below 1000..... And with it set that way, after fixing my timing which somehow was a couple degrees advanced, it idles perfectly at 950 with no surging or hunting which is new... Any ideas?


Oh yeah, I checked all 3 of my vac lines and they're fine. Vac at idle is the same as it's always been, which is bouncing between 10 and 12in hg at 950 rpm.