Although this doesn't explain the low sensitivity with injected stuff I think I may have the same issue as James Ball with the calibration valve closing during tune.
viewtopic.php?t=46621#p223251I ran the tune again today. The vacuum went from 2E-5 to 4E-5 and the first couple tune screens were good. Then it went back down to 2E-5 the ions went away. I got the the usual small noise peaks.
I tuned my 5975 and the vacuum stays at 4E-5 throughout the tune.
The question is why would a calibration valve close during a tune as opposed to just sticking closed. Do you think I can take it off and try rinsing/sonicating it with some methanol if it is gummed up?
BTW it always clicks and sometimes the vacuum reading doesn't change and it doesn't show good tune screens at all. Thanks for staying with me through this thread btw.