Depress EGR Valve While Idling

[DaveyX87]

I was trying to find a post about this specifically. I was checking for vacuum leaks recently and while the engine was idling I depressed the EGR with my fingers and the engine would want to kill. As soon as I let go, the engine would return to idle. Is this indicative of a good EGR valve or a bad one? I'm just trying to get to the bottom of my slightly rough idle. Most likely the rough idle is the result of a bad o2 sensor causing a rich condition, as pointed out by a fellow member. However, I am curious about the EGR. I don't plan to eliminate it for emissions reasons, just replace it if it's bad. Also, my TT chip should bypass the EGR anyway, right?

 

[markboss]

Sounds normal..

 

[earlbrown]

It's normal. And yes, your EGR is disabled with the TT chip.

 

[34blazer]

The purpose of EGR is to introduce inert and partially burned fuels back into the engine, but mainly its inert gas. When you opened the EGR valve by hand, the VE of the engine was reduced, and required a lot less fuel due to the inert gas displacing oxygen from the incoming air charge, that is why the engine almost died, the fuel trims couldn't change fast enough(reduce fuel needed, Integrator). If you watch your BLMs when you manually open the EGR, they would drop significantly, most likely to the lowest BLM allowed, iirc 108.

I saw your other thread. Looking at the numbers I could see the BLM was a little higher than normal. I like to see 128 give or take 5. A BLM of 128 is no correction based on O2 feedback, if its higher, the ECM is correcting by adding to the fuel trim. I didn't see anything about your current engine configuration. If the engine is configured with the PCV system but open breathers, that could be the cause of the higher than normal BLM, due to some air charge bypassing the MAF meter, which the ECM will only calculate for the measured airflow. When I had the MAF on my car, the BLMs were around 136 with the PCV connected and open breathers, closed it was right around 128. The O2 voltage should average .450V at idle, iirc. I need to verify by looking at a factory bin, but it should average .450V.