Any guidance on this would be much appreciated. The aecondary air injection ("AIR") pump My 98 Golf (A3) has started coming on when it shouldn't. I've read up on the subject in my Bentley manual and according to that, the AIR pump is supposed to come on for about 65 seconds during cold starts ("cold" defined as 58 to 95 F) and otherwise "briefly" (for about 5 seconds, it says later) as the computer goes through its diagnostics during warm starts.
Mine also has started coming on at random times when the car is running. I was guessing 3-4 seconds, so it might be the warm start "brief" time the manual mentions for warm starts. It happens like clock work some time after cold starts, before the engine is fully warm, when I'm sitting at an intersection about 3-4 minutes after leaving the house. But it also happens at other times when the engine is at normal operating temperature. l only notice it when sitting at idle but wouldn't be surprised if it is happening randomly at other times as it wouldn't be noticeable over road noise. It's always the same 3-4 seconds, the idle roughens a little, I hear the pump spinning, it stops.
Has anybody seen anything like this? Any ideas? It seems like the computer must be making this happen but why it would do that, I have no idea.
Thanks in advance for any help you can offer.