Alpine951

Just pulled the car out of hibernation.. Last year I developed a lumpy and very lean idle. It all happened last year after a wide open throttle run on the highway in 4th gear. I previously installed a new Vitesse maf and the car had been awesome but never had I gone WOT. Everything pointed to an intake leak but I have yet to track it down. Today it started idling high and then would drop., then high then drops. Took a video of the tach on my phone . hopefully it will work. what would cause this?


http://i130.photobucket.com/albums/p267/alpine951/Mobile%20Uploads/tmp_441-VID_20160430_113945791-2120811900.mp4


http://i130.photobucket.com/albums/p267/alpine951/Mobile%20Uploads/tmp_441-VID_20160430_113945791-2120811900.mp4

Tom M'Guinn

My guess is a vacuum leak. When the throttle switch is closed, the injectors shut off above about 1600 rpms. So when you have a leak, the engine starts to rev until it gets to 1600, then fall back down when the injectors shut off, then starts climbing as soon as the injectors turn back on -- over and over. The boost gauge also show the vacuum dropping (less vacuum) when the rpms drop, meaning airs getting in. Could be other things for sure, but if it happened right after going full boost, something probably popped loose from the pressure, like an intercooler coupler or other larger intake hose.