When testing the vaccum on an EGR valve, should the vacuum be a fixed rate, or does the vacuum adjust according to engine load by the ECM?

And should there be like a 'minimum' vacuum level, sort of a stand-by kinda thing?

If the valve is 'sticking', and the vacuum is not sufficient to open it, will the solenoid 'give up' or will the vacuum remain very high?

Cheers,

I think the vacuum at the vavle should be constant.
The transducer is activated by exhaust pressure. As the exhaust pressure rises, the transducers opens the valve to the vaccum line to allow it to open the EGR vavle. The transducer is variable, but I don't believe the vacuum from the manifold to the vavle is variable.

Actually, the EGR works most of the time in low idle, and low demand stituations, like warm up and sitting in traffic. It helps to keep the emissions down by reburning un-used hyrocarbons. It is a known fact that with out this thing, motors make more power, but I dont think we need to touch on the legallity of tampering with emissions equipment. Now if you are losing power, that means that it is stuck open, and is constantly burning exhuast fumes, and the more load, the more fumes, the less power. If it didnt pass emissions, it is stuck closed. Most of these happen do to carbon build up, which in this part, is unpreventable. Each brand sets thiers up differently, thus I cant say whether the vaccuum should be constant or variable. But MY thought is, that most of them, close as the enigine loads, thus, increasing vaccuum. Basically, the more air an engine PULLS into it self, the more likley that EGR is closed..

Hope that helps...

Chase

By the way, not fact on ALL EGRs...

The purpose of the EGR is not to reduce unburned hydrocarbons. Instead it is designed to reduce NOX formation by reducing high temperature situations. It does that by recirculation burned exhaust gases back into the combustion chamber. These gases then act as a diluent which in turn lowers the combustion temperature.

That being said I don't know the answer to the original question. My guess is that the solenoid is energized stictly under computer sensor control. The valve will open in varying engine conditions thus the vacuum it sees will vary but will primarily be during high load (i.e. high temperature situations).

I stand corrected on which particular gas it was that got recycled..but just the same. Regardless, EGRs were around well before ECMs and such. I have never seen one with wires that would cause it to be contrioled by the comp. Anyway, I dont know everything about the Isuzu motors. Anyway, to the best of my knowledge, it is controled by demand, BUT, I could be wrong. Anyway, I hope this bit of info helps.

Chase

Chase, I am talking about the 2.6 motor. I do not know the EGR system on the 2.8V6's.
EGR does not work most at idle on this motor(2.6), it works more as the throttle opens. If you open the EGR under idle with the motor, it will kill the engine. The vacuum solinoid is on a thermistor and as the engine warms up, the solinoid opens to allow vacuum to the transducer. When the transducer gets exhaust pressure, it will open up and allow the vacuum to reach the EGR vavle to open it and allow the exhaust gases in to the intake stream. The exhaust pressure will still open the transducer and allow the path of vacuum to be available to the EGR under cold conditions, but if the thermistor isn't warmed up and open, it will not allow the vacuum over to the transducer.

Also, there are electronically controlled EGR vavles, as the second generation Troopers are controlled this way.

I guiess I didnt remember correclty