Idiot light. On the highway. 86 GP, 305

[Bonnewagon]

By reading the book is says the ECM pulses the EGR rapidly and senses the change in manifold vacuum to determine if it's responding properly. Anything amiss sets the code so it is either a vacuum issue or mechanical issue. I was wondering if you could just bypass all that, and hook the EGR valve right to ported vacuum? Then just disconnect the vacuum sensor and the ECM will be blind . Only fly in the ointment would be if the ECM sets a code when it no longer has that 5 volt reference and vacuum signal. If not, problem solved.

 

[carpenter383]

By reading the book is says the ECM pulses the EGR rapidly and senses the change in manifold vacuum to determine if it's responding properly. Anything amiss sets the code so it is either a vacuum issue or mechanical issue. I was wondering if you could just bypass all that, and hook the EGR valve right to ported vacuum? Then just disconnect the vacuum sensor and the ECM will be blind . Only fly in the ointment would be if the ECM sets a code when it no longer has that 5 volt reference and vacuum signal. If not, problem solved.

The code would set if you bypassed the sensor/ egr controls.
The prob with hooking straight to ported vaccume would be the egr valve opening on acceleration. This would almost surely cause hesitation and spark knock.
The simple thing to do is block egr function and either live with the light or take the bulb out

 

[ilduce]

By reading the book is says the ECM pulses the EGR rapidly and senses the change in manifold vacuum to determine if it's responding properly. Anything amiss sets the code so it is either a vacuum issue or mechanical issue. I was wondering if you could just bypass all that, and hook the EGR valve right to ported vacuum? Then just disconnect the vacuum sensor and the ECM will be blind . Only fly in the ointment would be if the ECM sets a code when it no longer has that 5 volt reference and vacuum signal. If not, problem solved.

Was what I described with my EGR "vacuum hold" test correct? My theory is the seals or whatever in the EGR diaphgram (and my salvage yard unit) are shot, so the sucker loses the vacuum I plug it with after 10 minutes. If it's supposed to NOT lose its vacuum on on its own accord, maybe that's why I'm getting a light after ten minutes on the highway. Maybe the sucker loses its breath completely after ten minutes of first opening, valve comes down, ECM senses improper vacuum caused by that, and bingo. Dash light, rich fuel mixture, and less power up hills. $30 new EGR on Rock Auto. Of course that depends on if it's supposed to hold the vacuum, am I in the right direction?

 

[Bonnewagon]

No, I think you are good. Holding vacuum for 10 minutes is great, if it whoosed right out, then that's a shot valve, OR, it's a backpressure type valve. The manual stated that if it holds 10" vacuum, it's good, so it shouldn't be a backpressure type. Further, if pushing up on the backside of the valve causes the motor to idle rough, then it's clean and working. I think your problem is either the vacuum sensor or solenoid.

 

[megaladon6]

Dont forget about cracked vacuum lines