Yet another dreaded 401 thread....(few diag questions)

[RavenTai]

Gray,

Your Toyota mechanic buddy is incorrect, the cap is actually an air inlet and the filter filterers out dust from the outside air, if you have carbon in the filter area the diaphragm in the modulator has a hole in it allowing exhaust gas into the vacuum side of the modulator.

Here is the a pic of the diaphragm from my modulator, the hole did not show up well in the pics but you can just make it out, and the carbon from exhaust gases is plainly visible, the diaphragm is suppose to keep the exhaust gas in the bottom of the modulator separate from the rest of the system.

even though my modulator was "bad" and puking carbon into the system it still preformed its function of sending a vacuum signal to the EGR valve and ws not the source of my P0401, the VSV was, I just happend to find that wile looking.

 

[gray]

Raventai;

Thanks, great pictures; worth a thousand words; your explanation makes sense.

g

 

[Riad]

Yep, any kind of crack any where in the vacuum lines and/or in the modulator will throw the CEL/MIL, I am convinced. Nice detailed picture BTW Raven and thanks a lot for that. I had never seen the inside of the modulator until now.

I replaced my Modulator last year with a brand new one (blue top). I am almost to 1000 miles since my last CEL, should hit 1000 by end of this week. The new VSV is still in my parts drawer.

 

[98 SNAKE EATER]

1. If the VSV is commanded closed it should hold vacuum, if the VSV is open it will port ambient air defeating vacuum. the VSV is powered open so with the truck off it should be closed

OK, I did the vacuum test with the engine off, so it should have held...


Also, going by this pic (stolen from another thread), I pinched the hose with the arrow pointing to it with a needlenose pliers and when I applied vacuum from the EGR end, it held fine, so I'm pretty sure my hoses are ok....

As for the EGR valve itself, when I apply vacuum to it directly, the engine stumbles, but won't die because the vacuum is lost through the VSV....


However, if I pinched the same hose as above and apply vacuum to the EGR, the engine stumbles and shuts down



That being the case, it looks like the VSV is definitely the culprit


Light is still off, but I'm gunna order one anyways....

Gray,

Your Toyota mechanic buddy is incorrect, the cap is actually an air inlet and the filter filterers out dust from the outside air, if you have carbon in the filter area the diaphragm in the modulator has a hole in it allowing exhaust gas into the vacuum side of the modulator.

Happen to know which way your filter was installed?

My AllData guide says to install it with the coarse side up, but I've checked 6 different Toyota modulators in the last week and each one had the coarse side facing down






Rick

 

[RavenTai]

I do not remember, this is what the FSM says, I do not think that it is that critical


HINT:
Install the filter with the coarser surface facing the atmospheric
side (outward).


so that would be coarse side up,

 

[98 SNAKE EATER]

I do not remember, this is what the FSM says, I do not think that it is that critical


HINT:
Install the filter with the coarser surface facing the atmospheric
side (outward).


so that would be coarse side up,

That's exactly what AllData says, but it goes against all of the ones I've checked so far

 

[98 SNAKE EATER]

1. If the VSV is commanded closed it should hold vacuum, if the VSV is open it will port ambient air defeating vacuum. the VSV is powered open so with the truck off it should be closed

OK, I did a little snooping in my 91 FJ80 to see if the EGR will hold vacuum...

The VSV on the 3F-E is located on the left side of the bay so it's much easier to get to than my 97


With the engine off, it didn't hold vacuum either


Searched AllData for VSV testing and came up with this:

According to this, the VSV stays open and then closes when voltage is applied


AllData didn't show VSV testing for the 1FZ-FE


Any reason why it would work the opposite way though

 

[Riad]

The picture above is exactly the opposite for a 1FZ-FE engine ( I know I am repeating what you just said ).

Air will not (or should not) pass through when the VSV is "powered off" as Raven mentioned above. If it does then the VSV is bad.

I can't remember what the FSM says but I could not blow air through my brand new VSV that is sitting in my parts drawer (at home). I think there's a similar picture in the FSM for a 1FZ-FE, I can post it once I get home this evening.

 

[98 SNAKE EATER]

The picture above is exactly the opposite for a 1FZ-FE engine ( I know I am repeating what you just said ).

Air will not (or should not) pass through when the VSV is "powered off" as Raven mentioned above. If it does then the VSV is bad.

I can't remember what the FSM says but I could not blow air through my brand new VSV that is sitting in my parts drawer (at home). I think there's a similar picture in the FSM for an 1FZ-FE, I can post it once I get home this evening.

That's reasurring


Happen to know the correct part number and average price?


I ordered one from my stealership next door and my cost was $65 bucks


However, when I gave them the part number listed in another thread (part #90090-12079), it didn't show up on their computer

Their own listing didn't specify it as a "VSV", but I told them to send what they had anyways....

I'll find out in the morning...

 

[Riad]

You paid less than me, I think mine was $83.00 from Dan.

90910-12079 is what I've got.

 

[98 SNAKE EATER]

You paid less than me, I think mine was $83.00 from Dan.

90910-12079 is what I've got.

That's the number he gave me


Kewl beans

 

[Riad]

The picture above is exactly the opposite for a 1FZ-FE engine ( I know I am repeating what you just said ).

Air will not (or should not) pass through when the VSV is "powered off" as Raven mentioned above. If it does then the VSV is bad.

I can't remember what the FSM says but I could not blow air through my brand new VSV that is sitting in my parts drawer (at home).

Well I was wrong :whoops: .

Apparently the picture posted from AllData is also true for a 1FZ-FE. Attached snapshot is from the FSM. My new VSV works the same way, meaning I can blow air through it with no power (just checked again). My mind was playing tricks with me when I was typing that post

 

[98 SNAKE EATER]

Well I was wrong :whoops: .

Apparently the picture posted from AllData is also true for a 1FZ-FE. Attached snapshot is from the FSM. My new VSV works the same way, meaning I can blow air through it with no power (just checked again). My mind was playing tricks with me when I was typing that post

Yikes, not exactly what I wanted to hear


I'm gunna yank it anyways and test before installing the new one...

 

[landtank]

The picture above is exactly the opposite for a 1FZ-FE engine ( I know I am repeating what you just said ).

Air will not (or should not) pass through when the VSV is "powered off" as Raven mentioned above. If it does then the VSV is bad.

I can't remember what the FSM says but I could not blow air through my brand new VSV that is sitting in my parts drawer (at home). I think there's a similar picture in the FSM for a 1FZ-FE, I can post it once I get home this evening.

FYI, switches are described as NO (Normally open) and NC (normally closed). The term "normally" means without the trigger voltage present.

What you wrote contradicts itself. Being "powered off" would indicate a NO switch that was closed when power was connected. Then you wrote that the VSV sitting on the bench would not pass air so it would indicate a NC switch. Not meant to break balls but just trying to help clear some of this stuff up for those who might have problems understanding whats being written.

 

[Riad]

Thanks a lot Rick for clearing that out

Sorry for creating all the confusion.

Snake, Yeah, you should be able to test it easily after yanking it but make sure you don't have any kind of vacuum leak when you install it. Some times damages can be done simply by pulling those hoses. That's why replacing them with new ones would be good.

 

[RavenTai]

Well I was wrong :whoops: .

Apparently the picture posted from AllData is also true for a 1FZ-FE. Attached snapshot is from the FSM. My new VSV works the same way, meaning I can blow air through it with no power (just checked again). My mind was playing tricks with me when I was typing that post

Raid, my bad I got turned around at some point, the valve is normally open, i will try to straighten that out in the posts above.

so

1 with no power applied the VSV is open and the EGR cannot operate,

2 With power applied the VSV is closed and the EGR is armed and can operate as the EGR modulator dictates.

That FSM ref you posted is the VSV for the fuel pressure regulator, it lives in about the same spot as the VSV for EGR but at the front instead of the back, but you are correct none the less.

The Toyota training manual I have says the VSV's can be normally open or normally closed (all Toyota vehicles), according my FSM and the 3FE all data link above the 80 series land cruiser EGR VSV's are all normally open,

Here is the 1FZ FSM ref for the VSV for EGR

 

[98 SNAKE EATER]

OK, the new VSV showed up at my shop this morning (PN#90910-12079)


It's definitely normally open as I can blow air through it


Don't have the time to install it today, but I did manage to shoot a short video of how I tested the EGR valve and the VSV hoses for leaks



http://www.youtube.com/watch?v=CsZV5YbWOQ0


Note: when the VSV hoses are pinched, the EGR valve holds vacuum just fine and since it stalls the engine instantly, I've pretty much ruled it out as a problem...





Rick

 

[98 SNAKE EATER]

Well, I've got good news and not so good news




Good News

Installed the new VSV today and it only took 25 minutes total (15 to remove, 10 to replace)

Hardest part was taking off the damn intake bracket cause the lower bolt was rusted, but a pipe and some leverage broke it free

Also, one of the hoses on the old vsv was stuck, so I cut off about 1/2"





Not So Good News

Going by the FSM, my old VSV checks out ok

There's no continuity between either terminal and the body and it clicks shut when voltage is applied (no air passes through on juice)




The MIL's been off all week, so I didn't clear her yet...


Gunna run her as is and see what happens...







Rick

 

[bigjer]

EGR 401 code

I just bought a 97 40th edition and just after I got it it threw a CEL which was a P0401 code. Toyota mechanic could not find out what was causing it. Temp sensor was working fine. Cleaned the filter in the modulator which was dirty and the rough side was up. Checked all vac hoses and found some cracks in some of them. The code has not come back on yet but if it does I will check the VSV valve to see if thats the one. CEL's piss me off

 

[landtank]

I believe that a dirty filter might indicate a bad diaphragm in the modulator