So last week coming home my check engine light comes on. I do not notice any real change in performance. The on-off ignition test yeilded a code 25 "Idle air control motor circuits" and when I took it to Advance Auto they pulled code P1294 Target Idle Speed Not Reached. I think I have a vacuum leak (I can hear it) I just can not locate it. I have the upstream and downstream O2 sensors to replace, I just have not figured out how best to remove the upstream sensor. Since the code 25 came up I am not ruling out the Idle Air Control is bad, I cleaned it back in July when I replaced the plenum gasket.

I guess I am hoping you guys may be able to help shed some light on what may be cause the check engine light and code (maybe a specific vacuum leak to look for (it sounds like it is coming from right at the back of the engine block). and maybe a suggestion on the best way to approach the upstream O2 sensor.

Thanks.

 

Is it idling too high, or too low?

 

I have not noticed a major change in the idle, if anything maybe a little high. There error just appeared within two miles of the house and I have only driven it up to advance auto since and just did not notice anything different or alarming.

 

Clear the code, see if it comes back.

 

A faulty IAC will make a sucking sound and result in high idle. Normal is about 650 rpm when it's warmed up.