After new plugs, new intake manifold, egr and egr cooler. Prius idles rough. Got EGR low flow code after highway drive. She runs ok down the road. Very rough at idle. I’m thinking vacuum leak, but where? Any help appreciated
Need some more deets. Who did the work? NEW intake manifold? how the heck did you wear out the OLD intake manifold?? See also: EGR/EGR Cooler...... Yeah...there's something going on. Make sure you (or somebody else) didn't miss something on the re-assembly. Also...check and maybe clean your mass air flow sensor. Coolant level.... Dipstick....
Vacuum leak is plausible. It would otherwise be very difficult to explain a low EGR flow code (I assume you mean P0401 ... for clarity, I advise everyone to include the actual codes in posts, not just paraphrases) right after putting on new or freshly cleaned EGR components. But the car measures the EGR flow by comparing the vacuum without EGR to the vacuum with EGR, so if there is some leak reducing the vacuum without EGR, then that can make the EGR flow measurement come out artificially bad. There are a few vacuum connections to the manifold that would all have been disturbed in the work that was done, so I'd certainly start looking at those.
