1128/1130 code problems

[idrivea]

Hello all,

1997 2.5

I'm having trouble identifying what causes my 1128/1130 codes. Here's the situation:
For about a year, 1128/1130 code would come on and then go off after less than 50 miles. This happened every few months. A while back, the codes came on and did not go off, even after resetting them. I pulled out the MAF and cleaned it, which made the car run better, but it still idles high (~800-1000) and doesn't feel as powerful. The idle hunts in a range of ~100rpm. Cold start throttle response is sporadic, but improved a bit after cleaning MAF.

I don't have a durametric tool, so I can't get MAF voltages. The next thing I suspect is the AOS, so I checked the oil cap. I can get it off while running and the car shutters when off, indicating that vacuum is being pulled through the system. One suspicious thing is that when I change the oil and fill new oil, some spills through, but I'm not sure where. However, the vacuum being pulled would indicate that this is not a problem. With the engine cover off, there is a whistling noise in the engine bay, but I'm not sure where. It is only present at idle or low throttle i.e. it goes away when giving throttle.

MAF sensor is quite expensive and the AOS looks to be difficult to replace. Any ideas?

Thanks

[The Radium King]

The oil fill pipe runs from the trunk to the top of the engine. It is plastic and gets brittle with age. Further, the end at the trunk is fixed but the end at the engine moves with the engine, so the pipe gets worked mechanically on a constant basis. If it cracks you will get oil on the engine when you fill, or during high g cornering. Further, if it is cracked and is drawing in air, it will affect vacuum and Maf readings. Note that another mechanism that will crack this pipe is a failing aos that adds excessive vacuum to the crankcase; the vacuum can try to collapse the fill pipe and cause it to fail.