EGR valve diagnosis

I checked the EGR valve and applied vacuum and the engine stumbled and almost shuts off. Therefore, I feel the EGR valve is okay. I performed the steps 1-6 and at 2500 cold with the jumper installed, I got zero vacuum. At 2500 with engine at normal operating temperature, the vacuum did not respond abruptly while reaching 2,500 RPMs, but it slowly increased only to 3-4 inches Hg. I did not feel that I saw a definite reaction at 2,500, but a slow increase after reaching 2,500. While I was doing all of this, I removed the old modulator and compared it to a brand new one that I bought and the large port that is on the bottom of the modulator would not hold a vacuum while the new part would, so I deemed the old modulator bad and installed the new one. I took the car for a test run and it did not stumble at idle, but it still performed sloppy on the highway. Since the only other component is the VSV under the intake on the rear of the engine, I feel that I should replace the VSV. Steps 7-9 seemed a little unclear to me, but since I put a new modulator in and deemed the EGR valve itself okay, I feel that the VSV is not performing as it should. Any suggestions?

I put a vacuum/pressure gauge on the hose from the side of the EGR to the bottom of the modulator, and I feel pressure, but see only a flutter on the pressure gauge. The flutter does not even register 1 PSI. The backpressure in that hose to the modulator is something I cannot say for certain if it is acceptable. It seems as though this pressure to the bottom port of the modulator should be smoother. I took the old modulator apart and examined the diaphragm. It had a tear in it. I took pictures and will try post them tomorrow. I think my question right now is, does the VSV remain energized at all times when the engine is at operating temperature and only allows the vacuum to flow through from port Q of the modulator to the top port of EGR valve diaphragm? I just can't figure out why there are still drivability issues with a seemingly good EGR and a brand new modulator.

I have a new VSV and I am planning to change it. I just feel that the exhaust back pressure to the modulator is not enough. Have there been cases where the supply of exhaust pressure to the bottom of the modulator is not enough (from the port on side of EGR valve)? I am wondering what good pressure would be when I rev the engine with a pressure gauge on it. I could not get above 1 psi on my test. Could the EGR be clogged at the supply port for exhaust to the bottom of the modulator? I am still going to change the VSV since it is original. I have some pictures to share. I have a picture of new modulator on car, new modulator diaphragm holding vacuum (even though it works off of pressure), top of old modulator showing ports, inside of old modulator torn, in half, and carbon inside with water (not sure how moisture got inside there but there was).

What type of CRC cleaner would you use? There are different ones.

I changed the VSV and it seems that the car is about 95% better. I took it for a test run after and then a normal day of driving to and from work. The idle stumbling problem appears to have vanished and there is a slightly noticeable chug on the highway when releasing the pedal and coasting at highway speeds and throttling back to highway speed. However, I still have a problem with the connector to the VSV itself. The connector will not "clip" onto the VSV because the plastic is brittle and the clip broke. I want to buy a connector and extract the pins and replace the connector on the wiring harness without cutting the existing wires from the engine harness. I just want to replace the plastic connector. There is a slight oil leak from the engine and over time the oil gets into the connector if it is not sealed. I have a picture of the old VSV and a high Ohm reading. The new part read about 37 ohms while the old part was over 200 ohms. Take a look and let me know what I can do with the connector. Can I buy the connector from Toyota and remove the pin and wires from the old connector and replace it into a new connector?

Okay. Thanks for the information! I think I will try the dealer for a nice pigtail with wires. I am coming up with not much on searching elsewhere. Any ideas? I think the only things I have left to perfect the EGR system would be to clean the EGR with CRC as you suggested already and solder a new pigtail on the VSV because I am still getting a slight chugging at highway speeds when releasing the throttle and taking foot off the pedal. Have not experienced any idle problems so far with everything connected.

I was planning to remove the existing EGR valve and inspect it and clean it since it costs about $150.00. I will make a decision to keep it or replace it once I remove it and inspect it since it is operating okay. As far as the pigtail, it goes on the VSV which is only subject to the heat of the engine block because it is mounted to the back of the engine on the intake manifold and not directly to the EGR valve itself. I understand how the EGR valve and piping can be hotter. Thanks for your input. I will try to go to the dealer and see if the have the weather pack connector/pigtail. I agree that a genuine part would work best for sure as far as fitment and durability. I agree with you! Thanks, Danny! It will be hard to solder it given the location of the VSV valve, but I'll try.

I went to the dealer after asking if they sold a "pigtail" with the wires already inserted into the connector and they said no. Therefore, I found the 5 digit number on the connector which was 11156. The parts guy used this to find the connector shown in the picture. I plan on removing and re inserting the existing wires into the new connector since the brittle plastic of the old connector is my main concern right now and Toyota only has the wires with terminals already crimped for $31.00 each! I want to see how using the existing wires works with a new OEM Genuine Toyota connector. I have pics of the new connector and the old connector where you can see the 5 digit number slightly. Enjoy the pics!

A little update: I am still experiencing chugging on the highway. This happens when I am at highway speeds and I open the throttle slightly off the closed position back and forth when I need to coast if the car in front of me is going slower and I need to slow down. Therefore, I still feel that the modulator and the VSV may have been a contributing factor in the problem, but since when I pull the vacuum hose off of the EGR valve, the problem goes away. So, I feel the EGR is the problem in a way and I need to remove it and clean it even though it causes the car to die when a vacuum is placed on the diaphragm to check it. I have replaced or inspected everything else other than replacing the connector to the VSV. So, I need to clean the EGR and change the VSV connector. I will update you after I do these things.

I have changed the connector to the VSV, and still experience the same chugging. I will have to remove the EGR valve itself and clean it or replace it. Then I will test it again. Removing and either cleaning or replacing the EGR itself is the only thing I have not done so far. When I find time to do the EGR valve itself I will update everyone. Right now I have the EGR vacuum hose to the EGR valve disconnected and the car runs fine. However, I want to have the system working properly. So, I will have to remove the EGR and either clean or replace the EGR valve assembly.