Toyota Repair: 86 4Runner EGR, egr system, egr valve

Question
Hi, 1986 Toy 4runner 22REC EFI, man tran, 230k on vehicle, 5k on rebuilt engine, recently purchased, having problems with smog due to high HC at idle and at 2500rpm. Had to correct some misrouted vacuum hoses I found after the mechanic said there was constant high vacuum to the egr valve.(P & E ports on the intake manifold were reversed and the egr valve had been connected to the fuel pressure relief valve [?-go figure--?] Also replaced the egr modulator which had apparently cracked an internal diapragm. While bench testing the EGR valve, it seals well, and opens smoothly when I apply vacuum but it "leaks down" (closes slowly over a few seconds) unless I apply more vacuum. Shouldn't it hold the open position until I release the vacuum (I'm using a hand-held vacuum pump and visually observing the valve)? Also when performing the hot engine test of the bvsv and egr modulator (3500 rpm, R port of modulator connected to a good manifold vacuum source)I do not get the high vacuum reading I should at the egr valve side of the modulator (Q port) unless I pinch off the hose to the egr valve. I suspect a vacuum leak inside the egr valve body. Would this contribute the high HC? (I understand the egr system is to reduce nox.)(of course I suppose the vacuum hose routing could have been the problem)  I am having it retested this week. As I have been quoted over $200 for a new egr valve (part only - no labor) I would appreciate any ideas or thoughts before I proceed. Thanks -kenny-

Answer
High HC readings are normally caused by an engine misfire,
hydrocarbans are unburned fuel which means that the engine is not using all of the fuel it receives, this is not caused by a malfunctioning EGR system the sole purpose of which is to reduce NOX. High HC can be caused by an air intake leak, a leaking valve, a misfire(low compression)do not confuse this with a run rich condition in which case the engine burns all the fuel which will cause black smoke from the tailpipe and cause high CO.