94 Subaru Impreza Failed EGR Functional Test

So I get my Subaru smog tested at a local shop and everything passes except for the egr valve functionality test. The technician explained to me that the car should stall when the egr valve is manually despressed with his hand during idle. My car doesn't completely stall, but the rpms definitely change and the car starts running rough. So the tech says that my egr valve and/or its passages are plugged. I go and remove my egr valve and clean it with some carb cleaner and a wire brush as well as the ports and the tubes. I'm pretty certain that the passageways are not clogged. I also know that the egr valve itself functions because when I hit the throttle, I can see the pidle moving up and down. So I go get the car tested again and I get the exact same results. Now i've read some subaru forums and other egr valve forums, and all of them say that a change in rpm and engine idling rough is all that is needed to indicate that the egr system is functional. I've read nothing that indicates the engine needs to completely stall. I'm not completely sure how the design works, but it egr valve appears to be connected to only one cyclinder on the box 4 style of engine. If the egr valve only affects one cylinder is that enough to completely stall the engine? What should I do? Should i get it smog tested else where? Any input from you guys would be welcome. P.S I'm not 100% sure if this car is a CA model(I bought it in Oregon), so I don't know if that could effect the smog testing. Can I tell if its a CA model from the VIN #?

Answer:

The California Smog Check Procedures Manual prescribes EGR functional testing be conducted as required by the vehicle's manufacturer.

The following is Subaru's EGR Function Test Requirements:

Disconnect vacuum hose from EGR valve. Run engine to normal operating temperature. Attach a vacuum pump to EGR valve. With engine idling, apply 8 in. Hg to EGR valve. If vacuum holds and idle becomes unstable or engine stalls, EGR valve is functioning properly. Reconnect vacuum hoses. Increase engine speed to 3000-3500 RPM. Ensure EGR valve opens.

The definition of "unstable" idle speed is left up to the smog technician. If you feel certain there is noticeable drop in your Subaru's RPMs upon the opening of the EGR valve and in fact the engine becomes unstable (not simply running at lower RPM) then we'd recommend visiting another smog station for a 3rd inspection. If however the engine is simply running at a lower RPM with the EGR valve open we have to suggest looking further into the passages on both ends; intake manifold and exhaust. The EGR valve should be allowing exhaust gases to flow to all cylinders.

As far as the VIN number... yes, manufactures are able to tell whether a vehicle is California emissions equipped or 49-state. Contact your local dealers parts department. They should be able to help.

posted by SmogTips Support