If I put direct vacuum to the egr while the car is running shouldn't the car stumble or possibly die out? I tried, nothing happens. I also replaced the egr solenoid today, ran the vacuum from under the throttlebody to the back port on the solenoid and then ran a vacuum gauge to the port that the egr line should go to. I taped the gauge to the windshield. Driving the car around at different speeds I never did see any vacuum on the gauge at all. Why not? I'm trying to chase down knock at about 4k. My timing is only set at 6*. Total timing in the chip is only supose to be about 35* total. I've tried bumping the fp up near 50 psi, no help. If I back off timing down to about 2 or 3* the knock stops. Any ideas?

Gary

 

EGR, I thought is usually working fully at higher speeds, RPM's. hmmmm...
Could your TB line be plugged???

Did your engine work fine with this setup before the knock??
If so, than I would look into the knock sensor, and see if you could possibly have a vacum leak.

I'll think on this and get back to ya

 

Knock is controlled by the ECM, retarding the base timing isn't a solution.
Exhaust gas recirculation (EGR) systems were created primarily to control and reduce nitrogen oxide (NOx) formation, and secondarily to improve engine performance with ping control.

An EGR failure will not only cause excess NOx, but will often entail enriching the mixture or retarding the total timing.
The positive back pressure EGR valve can be identified by the letter "P" stamped next to the part number and date code. A back pressure valve is easy to spot because its pintle shaft is much thicker than the single diaphragm type. This is so because the shaft is hollow. The hollow design allows exhaust gases to flow into the shaft and push up on it. When positive back pressure in the exhaust system is sufficient, the shaft raises up and seals the built-in control valve. Once the control valve is closed, it allows applied vacuum to pull up on the diaphragm. Without back pressure to lift the hollow shaft and close the control valve opening, the EGR valve will not hold vacuum. It is bled off to the atmosphere. This design modulates EGR flow by modulating the applied vacuum. As engine load increases, so does engine back pressure, which causes the control valve inside the EGR to trap vacuum and open up. To test this valve, bring the engine up to 2,000 rpms to create back pressure, then apply vacuum. EGR should open and cause a 100 rpm drop or more. Exhaust leaks or a modified exhaust system can create havoc here. Adding dual exhaust or headers on a car designed for a single exhaust will reduce back pressure and set a Code 32 on GM cars. Positive back pressure EGR valves are used in simple vacuum controlled systems, as well as more complex pulse width modulated applications.

EGR solenoids are used with all types of EGR valves, especially back pressure type valves. The EGR solenoid will have two or more vacuum lines and an electrical connector. The solenoid also has an air bleed and sometimes an air filter. Vacuum is bled off through the filter vent. The PCM uses the solenoid to regulate vacuum to the EGR valve. The vacuum can be manifold or ported vacuum. The solenoid is a vacuum switch with inlet and outlet vacuum ports. The PCM calculates intended EGR flow from various other inputs and then sends a pulsed "on/off" signal to the solenoid. No vacuum flows until commanded by the PCM. This signal turns the vacuum on and off in rapid succession. This is called "pulse width modulation." If the filter becomes clogged, the vacuum cannot bleed off and too strong a signal will be sent to the valve. If that happens, the EGR valve will open too much and cause a driveability problem.