After finally getting my APS plenum installed and without leaking coolant in the throttle body passage (bypassed it with a double barbed nipple fitting from a parts store).

I've noticed the idle doesn't sit at 800 like it used to. The lowest I've had it was 850, about half the time I drive the car and slowing down to a stop at traffic signals it'll idle at 1000rpm. The idle doesn't change constantly while sitting still, when it idles it will idle very smoothly and remain at a constant rpm however at different rpm. Also noticed upon engine cranking it peaks at slightly over 2000rpm instead of 15-1800rpm. I still have a CEL from the previous Crawford plenum that was actually warped and creating a severe air leak causing the car to stall at idle. So not sure if this idle is throwing any data trouble codes. I don't know if this is a normal characteristic of the plenum or if one of the seperate pieces to be threaded in for the vacuum lines could have a slight leak, but not sure why the idle which change back and forth still. Any help is greatly appreciated.

 

How long have you had this new plenum on? If it hasn't been long, I would assume that the ECU would just take some time to readjust to the greater airflow. Since the idle is pretty smooth, just too high, it doesn't sound to me like a vacuum leak. Try unhooking the battery for a couple minutes to reset the ECU and see if that helps.

 

I haven't had alot of time to drive the car (busy with work and use the daily beater) But I have put maybe 200 miles on the car since the plenum had been installed.

 

Car idles perfect now, I'm guessing resetting the ECU erased everything on the EEPROM and has no more data trouble codes.

 

Glad to hear that the problem is gone! How does the driving with the new plenum feel? Is there a noticeable difference?