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VSV or EGR problems, Please help

I am getting the usual EGR flow is low. If I put a vacumm on the egr the engine almost stalls out. With the engine cold I am getting 14 volts to the VSV at all times. Once the engine is warm it still shows

14 volts. The only way I get it to drop is when I rev the engine real quick, the voltage drops and goes back up again. I had a vacumm gauge on the line that comes from the VSV to the EGR and when the engine is warm it shows no vacumm. When I rev the engine the vacumm jumps for a split second and then goes back to 0. I put a jumper on the E1 and TE1 on the data link, the engine would rev for a second then almost die out. I was going to take the VSV off to test it with a meter but, I can't get the dang thing off. I was going to just buy a new one and zip tie it to the firewall, but I can't afford to just buy parts since my 2002 ford explorer is going to need a new transmission. Right now I am bypassing the VSV by running a vacumm hose from the regulator right to the egr vavle. Will this work for emission testing as long as the engine is warm ? Sorry for the mixed up post, bottom line my questions are: Is the VSV normally open or closed. Should it have 14 volts to it when the engine is cold ? Can I just bypass the VSV and pass emissions ? Could it be the Map sensor ? or something else.

Thanks again,

Reply to
BigB
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EGR flow should be low at idle.

BTW, what model, year, engine, are you talking about?

If I put a vacumm on the egr

If you apply vacuum to the EGR valve when the engine is idling, it should almost stall out so your EGR is operating properly.

With the engine cold I am getting 14

This is not the correct test procedure. Disconnect the VSV for the EGR and measure continuity between the 2 terminals. You should have between 27 and

33 ohms and when you blow in port E, air should come out of port G. Then apply 12 volts to the 2 terminals and when you blow in port E, air should come out of port F.

No. Applying vacuum to the EGR all the time should cause a rough idle.

See above.

NO!

You never described the symptoms you are trying to cure. What is going on and under what conditions?

Reply to
Ray O

96 Camry 5S-FE, EGR flow is low. It can go from a day to 3 weeks before the check engine light comes on.

I just get a check engine light, other then that the engine runs fine. I know that it holds a vacuum from the modulator to the VSV. I can blow air from the EGR to the VSV, but I have to try it with voltage and see where the air comes from. Should there be 14 volts at the VSV all the time even when cold ?

Reply to
BigB

I managed to get my meter on the VSV without taking it off and here is what I found with the engine cold. I showed 35.8 ohms between the two terminals on the VSV. I have continuity between the two terminals on the VSV. I did not have any continuity between either terminal and the body of the VSV. When I apply 12 volts I hear a click at the VSV. With the engine cold and the ignition off, I can blow from the EGR valve down to the VSV and hear the air come out of the filter. When I turn the key to the ignition (not running though and still cold) and blow air from the EGR to the VSV, the air comes out the hose that goes from the VSV to the modulator. With the flow going through the VSV and completing the loop to the EGR when the engine is cold seems wrong to me. What could cause this ? I can go anywhere from 1 day to 3 weeks before the check engine light comes on.

Reply to
BigB

From what you are describing about the checks on the VSV, it seems like it is operating properly.

If you got a OBD II trouble code P0401, check out this site:

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for hints.

You may want to check the operation of the EGR position sensor - it may sense that the EGR is not opening enough when it is.

You can go to techinfo.toyota.com and for $10/day, you an get online access to factory repair manuals.

The reason that the check engine light seems to come on randomly is that trouble code has a 2-trip detection logic and needs to sense the problem on

2 consecutive trips.
Reply to
Ray O

formatting link
for hints.

Reply to
BigB

The EGR position sensor will be on or near the EGR valve. I'll take a look at a service manual tonight to see how to test it and to confirm its location.

Reply to
Ray O

OK, I check a factory service manual, and the possible causes of a P0401 diagnostic trouble code (DTC) are:

1) EGR valve stuck closed - you already checked this so this is probably not the problem. 2) Open or short in EGR gas temp sensor circuit - we'll come back to this 3) Open in VSV circuit for EGR - you are getting voltage at the VSV so this is not it. 4) Improper operation of the VSV for EGR - you already check this so this is probably not the problem. 5) bad vacuum control valve (VCV) - we'll come back to this. 6) vacuum hose disconnected or blocked - hopefully, you already checked this. Manifold vacuum should be healthy. 7) bad ECM - I've looked at a pretty fair number of cars and have never personally run across a bad ECM and I pretty much always toss this cause out the window.

You can never mind what I suggested previously about the EGR position sensor.

The next step is to check the EGR gas temp sensor. It is located in the tube between the EGR valve and the intake air chamber. To check, disconnect the wires from the sensor and measure the resistance between the 2 terminals on the sensor. Don't do this immediately after driving. Resistance should be between 2.5 kilo ohms and 600 kilo ohms. If the ohmmeter reads 750 kilo ohms or more or less than 200 ohms, replace the EGR gas temp sensor.

check the wiring to the EGR gas temp sensor to make sure it is not damaged or the insulation is nicked.

The VCV for the EGR is located between the intake air chamber and the VSV for EGR. There is no electrical connection to the VCV. It is a short round cylinder with 2 vacuum hoses. To check the VCV, unplug the vacuum hoses, hook up a Mighty Vac to port S and plug port Z with your finger. Pump the Mighty Vac 3 times so it reads between 8.6 and 11.8 in Hg, stop pumping, wait 10 seconds, and check the gauge. It should read between 4.4 and 7.1 in Hg. If not, replace the VCV.

That's about it, if these don't work, I'm out of ideas.

good luck!

Reply to
Ray O

For the temp sensor I only have the EGR valve and a tube that goes right to the engine, there isn't a sensor on it. This isn't the map sensor mounted on the firewall or one right around the air intake is it. I am going to borrow a vac pump today and test the VCV first. Thanks for all your help.

Reply to
BigB

No. The system has to have a way of detecting EGR flow, I'm not sure how that happens on your particular car.

I recommend paying for access to techinfo.toyota.com (I think it is $10/day) for the pdf version of the factory service manual for your particular car. Check the engine (EG) section in the manual under code P0401. Keep in mind that the manual often refers to other sections for testing a particular component like the VCV.

good luck!

Reply to
Ray O

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