Slightly high idle and a p0401?

[4orRunner]

I am still trying to track down what is causing the p0401 on my 2.7 runner. I am beginning to suspect an air leak at the manifold or TB.

1. The truck is now idling at about 900rpm vs. the 700ish it was before.

2. When I crack the throttle open at the the TB there is a noticeable whistle and air rushing noise that I did not notice before. I can also hear a constant slight whistle when the truck is just idling. It sounds like it would if it had an aftermarket intake or something.

3. There is next to no vacuum coming out of the ports on top of the throttle body.

4. Fuel mileage is bad and engine seems sluggish.

So my primary question is, is it an air leak or something else causing my problems?

 

[St Runner]

p0401 is insufficient recirculating gas flow. Most often caused by the egr valve or the vsv(vacuum switch valve). Its easy to check the erg valve just pull off the vacuum hoses, unclip it suck through the valve on the bottom. If you can only pull a little bit and it holds vacuum it is working, if you can keep sucking through it the diaphragm is bad and it needs to be replaced($70 online get the denso) That was the problem with my 2.7 and I did not have to go any further. You could have multiple problems with air leaks and vacuum leaks but I would concentrate on fixing the p0401 and then check all the air intake fittings band vacuum lines as a separate problem

 

[4orRunner]

p0401 is insufficient recirculating gas flow. Most often caused by the egr valve or the vsv(vacuum switch valve). Its easy to check the erg valve just pull off the vacuum hoses, unclip it suck through the valve on the bottom. If you can only pull a little bit and it holds vacuum it is working, if you can keep sucking through it the diaphragm is bad and it needs to be replaced($70 online get the denso) That was the problem with my 2.7 and I did not have to go any further. You could have multiple problems with air leaks and vacuum leaks but I would concentrate on fixing the p0401 and then check all the air intake fittings band vacuum lines as a separate problem

When you say EGR valve, I am assuming you are actually referring to the EGR modulator. I have not tried applying vacuum to the bottom port of the EGR modulator, I will try that next. The EGR valve itself is working fine, as is the VSV. I tested it with 12v from the battery and it appears to be operating normally. My concern is that there may be no fault with the EGR system at all, and that there is in fact a large vacuum leak somewhere between the intake and the throttle body or an issue with the throttle body itself. I will test the EGR modulator and post the results.

 

[St Runner]

Its possible that a vacuum leak might lead to such low vacuum that the erg valve does not function and that is throwing a code. There is no code for a vacuum leak so I would follow the fsm and test as they recommend for p0401. At the same time I would go through all the intake and vacuum from the maf to the throttle body. Any air leak or vacuum leak in this area will cause issues but there is no sensor to throw a code. A can of carburetor cleaner carefully sprayed while running will help detect air leaks. Its also possible you might have to remove the throttle body and clean it and check each vacuum hose to make sure they are not blocked

 

[4orRunner]

Its possible that a vacuum leak might lead to such low vacuum that the erg valve does not function and that is throwing a code. There is no code for a vacuum leak so I would follow the fsm and test as they recommend for p0401. At the same time I would go through all the intake and vacuum from the maf to the throttle body. Any air leak or vacuum leak in this area will cause issues but there is no sensor to throw a code. A can of carburetor cleaner carefully sprayed while running will help detect air leaks. Its also possible you might have to remove the throttle body and clean it and check each vacuum hose to make sure they are not blocked

Unfortunately, I do not have access to a FSM for this engine so I am using every bit of knowledge I can find online.

The truck was idling fine before the last time I took it apart. So I figure I must have fudged something by not connecting a line or maybe the intake or throttle body aren't on quite right and its causing a leak.

I figure cleaning the throttle body would be a good idea nonetheless. Just in case there is any obstruction. What is the best way to clean it without harming anything?

I am still curious as to what the air rushing noise is when opening the throttle quickly. I am thinking it could be my smoking gun as to what the problem might be. Maybe I'll take a video and upload it so other members could give their input.

 

[bentos1]

Unfortunately, I do not have access to a FSM for this engine so I am using every bit of knowledge I can find online.

The truck was idling fine before the last time I took it apart. So I figure I must have fudged something by not connecting a line or maybe the intake or throttle body aren't on quite right and its causing a leak.

I figure cleaning the throttle body would be a good idea nonetheless. Just in case there is any obstruction. What is the best way to clean it without harming anything?

I am still curious as to what the air rushing noise is when opening the throttle quickly. I am thinking it could be my smoking gun as to what the problem might be. Maybe I'll take a video and upload it so other members could give their input.

You might be able to find the 2.7 FSM here, Online Factory Service Manual | Tacoma Forum | 4x4Wire TrailTalk

I would think there would be one online somewhere. Do you have a Haynes or Chilton's manual?

 

[4orRunner]

Here is a clip of the noise I am referring to. I do not remember hearing it before.

<iframe width="560" height="315" src="https://www.youtube.com/embed/dffOu6EXxkU" frameborder="0" allowfullscreen></iframe>

 

[4orRunner]

You might be able to find the 2.7 FSM here, Online Factory Service Manual | Tacoma Forum | 4x4Wire TrailTalk

I would think there would be one online somewhere. Do you have a Haynes or Chilton's manual?

Those are for trucks with the V6. I haven't been able to locate one for my year (2000) and my engine (3rz).

 

[bentos1]

Those are for trucks with the V6. I haven't been able to locate one for my year (2000) and my engine (3rz).

This link shows a 96 3Rz

Free 1996 Toyota Tacoma Factory Service Manual (2)(3)RZ-FE 5VZ-FE:
http://www.ncttora.com/fsm/1996/96_repair.zip

The link is dead, but if you are sneaky you can use the internet archive.

Internet Archive: Wayback Machine
https://archive.org/web/

I found the zip and it looks like it should be able to DL, https://web.archive.org/web/20101127005057/http://ncttora.com/fsm/1996/96_repair.zip

I cannot try at the moment but let me know if it works.

 

[4orRunner]

This link shows a 96 3Rz

Free 1996 Toyota Tacoma Factory Service Manual (2)(3)RZ-FE 5VZ-FE:
http://www.ncttora.com/fsm/1996/96_repair.zip

The link is dead, but if you are sneaky you can use the internet archive.

Internet Archive: Wayback Machine
https://archive.org/web/

I found the zip and it looks like it should be able to DL, https://web.archive.org/web/20101127005057/http://ncttora.com/fsm/1996/96_repair.zip

I cannot try at the moment but let me know if it works.

It does work, but I noticed the manual says its for a 1996 tacoma. I assume that wouldn't matter much as they are both equipped with the same engine.

 

[bentos1]

It does work, but I noticed the manual says its for a 1996 tacoma. I assume that wouldn't matter much as they are both equipped with the same engine.

I bet that it will be the same or there were very small variations between the 3rz over the years. Hey, at least its an FSM. Its a start!

 

[4orRunner]

I bet that it will be the same or there were very small variations between the 3rz over the years. Hey, at least its an FSM. Its a start!

That's very true and I'm definitely not complaining. Thank you sir.

 

[4orRunner]

Just thought I would update this thread real quick.

I took everything apart, cleaned, and reassembled with a new VSV for the EGR.

I tested everything per Toyota's specs in the FSM for the 3RZ engine.

The VSV is working properly (it better its brand new).

The EGR valve is working properly

The EGR modulator however is NOT working properly and it seems as if the diaphragm inside is broken.

I haven't ordered a new modulator yet but will be soon I am almost positive this should wipe the P0401 from the ECM.

Also, after reassembling I am happy to report the idle has returned to normal and there are no vacuum leaks anywhere.