Common P0401 DTC code, and random rough idle
I have done a lot of research and looking through the FAQs and other posts looking for similar issues to what I have, but am still looking for further ideas.
Scenario: A month ago my 99 Camry 2.2L began to have a "flat spot" or sudden acceleration noticeable at 2600 rpm. A week or so later the CEL came on, read code and got P0401. I trouble shot, found EGR valve good with hand vacuum, VSV checked out good but doesn't mean its not intermittent problematic, however I borrowed a VSV from a 91 toyota pickup, even though this VSV was opposite (vented in power off state) I just changed the hose routing to rule out that my VSV was not the issue as they want $75 for new one. Still got P0401. Tested modulator and has black burn marks on filter, and no vacuum at the bottom exhaust backpressure port, so thought that was it for sure and replaced it, but still get P0401.
So by disconnecting the vacuum hose directly at the EGR valve this should isolate the EGR system as being problematic, correct?, as I still get the rough idle at random times, even though it seems less frequent than when the EGR valve is hooked up, but I think that is just coincidence.
I know it not the usual but I suppose I may have two completely different issues at the same time?
The only other thing I can think to check is the MAP sensor.
And one thing I notice is the EVAP VSV I believe it is is cycling open and closed at about 1/2 second intervals at times. Not sure if that could be part of the problem or not but doesn't sound normal to me.
I just hope I can figure something out soon. Thanks for any advice and ideas!