Mechanics

I AM GETTING A P0402 EGR "A" FLOW EXCESSIVE HOW TO FIND EXACT CAUSE

1996 Toyota Avalon • 160,000 miles

If flow is excessive I tried fixing for a sticking egr valve. I vacuum it up and tap the valve a little with a screwdriver handle. I also think it may be the Thermo sensor(see in pics). I have another thermo sensor from junkyard. What are the values I test for on the thermo sensor? What other causes of this problem can you think of? There is no valve position sensor as you can see. I believe the thermo sensor is the only trigger for the ECM to say the flow is too cold or excessive? I am not sure on the function read by ECM can you clarify please? Thanks
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PCMentor29
October 15, 2012.




ALso I did a road test with vac gauge attached. At acceleration it would read between 5 -9 inHg vacuum. At WOT no vac and at no throttle no vac. This seem correct unless the value should be 5 inHg and any higher the modulator is at fault. Please let me know the correct vac reading. Thanks


Tiny
PCMentor29
Oct 15, 2012.
If you pull a vacuum on the valve with a hand vacuum pump and then release the vacuum does the egr valve stick open?I also posted the trouble tree for that code. Let me know what you find.


Saturntech9
Oct 15, 2012.
Thanks I will try.


Tiny
PCMentor29
Oct 15, 2012.
Your welcome keep me posted.


Saturntech9
Oct 15, 2012.
If you pull a vacuum on the valve with a hand vacuum pump and then release the vacuum does the egr valve stick open? No I did it 5 times(to 20 psi) and it snapped closed each time.

Also on the EGR Modulator, the filter on top was hard side down. I heard the hard/rough side goes up and the soft side down. There was a carbon deposit on the filter that may have plugged the vent hole under the filter. I will try driving for a while and see if the soft side down clears the high flow problem.

Also I tested the EGR temp sensor and got 150KOhms at 89.8 degF measured on the part. This seems ok as it's more than 2500 ohms. I also tested a spare sensor and got 273kOhms at 69.8degF. Which seemed ok.

Also I am confused as to how to carry out the following test procedure. How can I tell if theres restricted flow with the noise of the engine reving to 3500rpm? Is there a trick to it? Thanks

EGR VACUUM MODULATOR
1. Mark vacuum hose locations and disconnect vacuum hoses from EGR vacuum modulator.
See Fig. 26. Block ports "P" and "R" on EGR vacuum modulator. See Fig. 25.
2. Apply air pressure to port "Q". See Fig. 25. Air should flow freely through air filter side
of EGR vacuum modulator.
3. Start and operate engine at 3500 RPM. Repeat test procedures in steps 1) and 2). Strong
resistance of airflow should be felt. Replace EGR vacuum modulator if strong resistance is
not felt. Reconnect vacuum hoses to proper locations.
NOTE: When testing EGR vacuum modulator, it may be necessary to
monitor engine RPM by using scan tester. For scan tester
connections, see IDLE SPEED & MIXTURE in ADJUSTMENTS article.
NOTE: Ports "P" and "R" are the double ports on side of EGR vacuum
modulator. Port "Q" is single port on side of EGR vacuum
modulator


Tiny
PCMentor29
Oct 17, 2012.
Should I used 30psi air from a compressor and also remove the cap and filter to do the EGR Modulator Test? Is it even worthwhile to do this test? Maybe better to check if filter/port is blocked like I found. I am hoping it was the solution. Thanks.


Tiny
PCMentor29
Oct 17, 2012.
I would continue on the path your going and see how it turns out looks like you most likely found the problem. Keep me posted.


Saturntech9
Oct 18, 2012.
I drove it 200 miles today and no code. I parked it for 2.5 hours it cooled down and then drove 7 miles no code. That's great it may be solved. Thanks for your help.


Tiny
PCMentor29
Oct 19, 2012.
I donated $2, I hope you can buy a Mountain Dew with it. Thanks
AD


Tiny
PCMentor29
Oct 19, 2012.
Thanks for the donation did you donate it to this question?Also how did you know I liked mountain dew?


Saturntech9
Oct 19, 2012.

AD