First post here, so please be patient. I have a 1.6L '96 Corolla with 189--- miles on it. 3 or 4 months ago (~5000 miles) my CEL came on - code P0401 Insufficient EGR flow.
Originally, I checked the EGR Valve by applying a vacuum and it caused the motor to stall. The EGR modulator passed a small amount of air when I held ports P and R. Additionally, the bottom port held a vacuum so I believed the internal plastic piece was not torn. I then purchased a VSV from Toyota and cleared the code.
The CEL remained off until last night when it came back on. A quick run down to AutoZone revealed code P0401 again. This weekend I will repeat the above procedures and recheck the EGR and modulator. I am quite confused now because of the duration of time between the two errors. Does anybody have any suggestions about what is going on or what else might be suspect? Thanks for the input!