My 86 22R needs a California smog test and the egr is usually the main failure point. So I decided to check it out first before shelling out $85 for a test failure. I unhooked the vacuum line from the manifold plenum and applied vacuum. No change to the idle, no hesitation and no stalling. I had a spare egr and I installed it. Same issue, no idle difference. I can hear the valve close when I release the vacuum. This model year does not have any other egr components such as a modulator. Why would a seemingly good egr not cause some idle disruption when vacuum is applied at an idle? The truck is at full operating temperature with idle at or around 900 to 1000 rpm. Any ideas guys?

 

Carbon plugging egr passages??

Please show your egr diagram that uses no modulator, just curious. What controls egr function??

 

The EGR valve is mounted directly to the side of the head, the plenum tube runs to the top of the intake and vacuum is supplied from a plenum rail along the top of the manifold. No other components, vacuum lines or wiress are attached to the EGR assembly. I think that it is only vacuum controlled at higher RPM's.Thanks.

 

 

Thanks for that diagram.

 

The BiMetal Switching valve, has 3 vacuum ports, the top goes to the vacuum plenum line, the second one goes to a tee near the rear of the carb that has a plastic module that is yellow and white in color. The 3rd or bottom port on the BMSV goes to the front of the carb at the AAP diaphragm. Nothing else connects to the EGR except a vacuum line from the main plenum (vacuum rail) line.

 

All of the passage ways, tubes and lines are clean. The latest EGR is practically new and very clean. I can tell that it opens when vacuum is applied because after 30-45 secs, I release the vacuum and can hear the plunger (diaphragm) drop back in to place.

 

If a substantial quantity of exhaust gas was actually reaching the intake manifold at idle, the engine would stall

 

That is what is confusing me. I believe the EGR is fully open, but nothing is happening with the idle. Could there be some obstruction in the manifold, below the EGR plenum tube? It looked clear when I replaced the EGR and the tube yesterday. I installed new gaskets at the head and at the manifold.

 

Found that both diaphragms in each erg valve moved and created noise when vacuum was applied, but the Pintle shaft was not lifting high enough to open the valve to allow gas to reach the intake manifold. I used some carb cleaner and a plastic tie wrap to clean the port below and around the pintle shaft. This was much easier when the erg was removed and I could visually see all the components. I was able to apply enough vacuum with a small piece of tygon tubing and sucking on the end of the tubing. Yeah, I know I suck! Many thanks to Millball for his advise and time!