I just had a new OEM engine installed and am trying to diagnose some issues with idling and missing/hesitating on acceleration. When I fire it off, it idles fine anywhere from 10 seconds to a minute and then starts to drop RPM's and start stuttering. Also, a loud hissing can be heard from the air filter when this happens. If I raise the RPM's by 50-100 the hissing immediately stops and idle returns to normal for 10-30 seconds and this repeats.
I spent a while trying to find a vacuum leak but I haven't been successful yet. The MAF has been replaced as has the IAC valve. An interesting observation is that when the engine is hissing/missing, if I unplug the IAC the hissing immediately goes away but the engine RPM's stay the same. If I plug it back in again, the hissing returns immediately.
Any suggestions?
Video of hissing/IAC disconnect:
[ame="http://www.youtube.com/watch?v=s1MgnuZlkUI"]YouTube- New Engine break in[/ame]
I spent a while trying to find a vacuum leak but I haven't been successful yet. The MAF has been replaced as has the IAC valve. An interesting observation is that when the engine is hissing/missing, if I unplug the IAC the hissing immediately goes away but the engine RPM's stay the same. If I plug it back in again, the hissing returns immediately.
Any suggestions?
Video of hissing/IAC disconnect:
[ame="http://www.youtube.com/watch?v=s1MgnuZlkUI"]YouTube- New Engine break in[/ame]