Question 1: The breather valve on the front of the gas tank -just a breather? Any importance to the Evap system?

Question 2: Intermittent problem -
Recently, I've just replace the fuel pump on my '97 Blazer. It was lots of fun.*sarcasm* The breather valve on the front of the tank I was not aware was there. It did break but I've rigged it up where the hose is still connected. Intermitently I've been getting my engine light and the vehicle's been running rough. I suspect a misfire somewhere. When I got to work last week I hooked it up to our OBDII scan tool to check the codes. It's sending a #2 Misfire and an Evap code. Erased them -and again, they show. This is not every day nor is weather an issue. Plugs were just replaced about 1000 miles ago. And there's spark. I do plan on switching plug wires and trying to get the code. Only thing that baffles me is - everytime there's a misfire I get the misfire code and the Evap codes at the same time. I do NOT get the Evap code by itself.


Stumped.

 

what codes? if its a p0410, that ones not in the repair book (i think its a p0410). its the air pump under the front end, you have to take off the plastic shield to see it (6 15mm bolts). there was a service bulletin issued for it in all data. what happens is water gets in it and fuggs up the bearings. its controlled by the ecu - usually comes on at about 40-50 mph whiles cruising steadily. this is usually when the idiot light comes on. there is a replacement pump available, i have no clue what it costs though. i haven't replaced mine yet. unfortunately it sometimes triggers other codes such as egr, occansionally a cyl misfire and sometimes an O2sensor. I usually just reset the ecu and the light stays off for 1-2 months. Just my 2 cents.

 

oh yeah, to see if the air is the problem, disconnect the 2 wire harness from it and apply 12 volts to it. if it sounds like **** when it turns on, its the culprit.