I have a '93 PonGP with the 3.1 V6. Approximately 15 seconds after starting the engine there's a growling from under the hood. The sound is just like the growling you typically hear from a failing bearing on an accessory like an alternator or power steering pump. Doing the test I'm used to of placing one end a metal screwdriver on each accessory in turn and placing my ear at the other end listening for the familiar bearing growl reveals nothing. All sound OK including the Air Injection Pump - hereto referred to as AIP to reduce effort in this post due to primitive typing skills.
So I drive over to my local garage for some diagnosis assistance. By the time I get there the sound has all but diminished. "Not a bearing probably the AIP" he says - "not to worry forget it." So I return home , let the car cool down a bit. Start it up and Growling resumes.
The sound does indeed seem to be coming from the AIP area as far as I can tell but its not consistent - it disappears after a while. I know there's an ECM function to control a valve to output AIP air to the exhaust ports or the atmosphere.
So my questions are based upon the symptoms and the sound:-
Does the problem sound like the AIP itself of the valve?
Are the AIP and ECM controlled valve one unit?
Am I completely on the wrong track?
I don't want to stert replacing parts unnecessarily. Incidentally the engine seems to run fine and there's no check engine light illuminated. Any help or experience would be welcome. Thanks in advance.
