failed emissions (high NOx) (1 Viewer)

[DHwreckage]

Well i failed my emissions because of High NOx emissions, i have a few therories that i want to run by you guys.

My truck is throwing the P0401 code (low EGR flow) could that cause the higher NOx emissions?

could my cat be bad causing the NOx emissions?

would headers cause increased NOx?

could remnants of injector cleaner cause higher NOx?

Any other reasons a may have failed? Thanks in advance for your help.

 

[Pin_Head]

More likely an EGR problem because of the P0401. The EGR plays the main role in controlling NOx.

 

[mod5csi]

I just dealt with and fixed my P0401. All the troubleshooting is somewhat fresh in my brain (and tablet). If you want a hand DIYing the EGR let me know. Im down in Parker.

 

[DHwreckage]

I just dealt with and fixed my P0401. All the troubleshooting is somewhat fresh in my brain (and tablet). If you want a hand DIYing the EGR let me know. Im down in Parker.

did you just replace your EGR or go through the whole system and clean the port into the intake.

 

[Pin_Head]

did you just replace your EGR or go through the whole system and clean the port into the intake.

What needs to be done depends on what is wrong. There is an extensive trouble shooting guide that will quickly determine what is wrong in the factory service manual, which you can download if you search.

 

[mod5csi]

What Pin Head said...

My problem was a combination of clogged ports in the throttle body, bad EGR Modulator, and VSV, also the vacuum T on the EGR Valve was clogged. All of which I found by following the FSM. I PM'd the rest of the components also; new vacuum lines and cleared the tubes going thru the intake manifold, cleaned the intake chamber tube, temp sensor, and EGR valve itself.

 

[kerrye]

Simplest way to test the system is with a Mity Vac in my opinion. I put a thread up a few weeks ago on how to use one to test all the components except the temp sensor. If it's only a bad VSV, which is a common problem, sticking a BB in the hose which goes from the drivers side nipple on the EGR to the manifold will force the EGR to stay on all the time which will allow you to pass emissions until the new VSV valve arrives. It's what I did.

https://forum.ih8mud.com/80-series-...e-71-code-p401-high-nox-failed-emissions.html

 

[ChiTown]

I don't recommend leaving the EGR on all the time as you drive around. There can be some serious side effects. I just finished the EGR battle myself and its not that hard. Here are the basics so you don't have to sort through a dozen P0401 threads like I did.

You can pretty much resign yourself to replace the vacuum modulator and vsv solenoid. (Requires pulling the upper intake manifold)

You're going to need these parts:
Throttle Body Gasket 22271-66010
Upper to lower intake gaskets (2) 17179-66010, 17171-66010
VSV for EGR - 90910-12079
VacuumModulator for EGR - 25870-66011
EGR Valve Gasket - 25627-66010

After that make sure the large EGR port in the intake manifold is clean along with the small one running through the back side of the intake manifold and the two 90 deg. nipples on top of the throttle body itself (CA checks for vacuum at both of these for smog test)

Replace the rubber lines to everything as they are old and probably have the material in them from the blown vacumm modulator.

Test the EGR itself by opening it manually when the car is running at idle and the car should want to stall. You can do this by applying vacuum to one side of the T with the other capped.

If you need pictures thus is the best thread I found:
https://forum.ih8mud.com/80-series-tech/363575-p0401-defeated-pics.html

If you follow these steps you should be good to go.

 

[kerrye]

It's not literally on all the time. It's on when the modulator turns it on but never off when the VSV would normally turn it off. So, basically, it's on when it's cold as well as when it's hot. It's a temporary solution to pass the emissions test if the VSV is stuck open until you have a chance to replace the VSV.

 

[Timpanogos Slim]

There's a way to replace the VSV solenoid without getting under the intake. Basically involves longer wires and hoses and attaching a new VSV outside that area.

 

[mod5csi]

I can't disagree with anything that has been said. But dont just throw parts at it. Although if you are going through the trouble of taking the upper intake manifold off to test the VSV, you may as well replace it or at least relocate it.

There are plenty of threads and advice here on MUD and Snake Eater even did a quick youtube video on testing an EGR valve.

Here are a couple of links that I found useful, if you dont mind not buying your parts from Toyota.

Blue Label Vacuum Modulator This is the same for the temperature sensor. The temp sensor has a TEQ marking on it just like the OEM Toyota. I have an extra Temp Sensor if anyone needs it.

Auto Parts store "universal" VSV

Again though. Troubleshoot and fix whats wrong, dont just throw parts at it. And PM all the other components while youre in there.

 

[DHwreckage]

thanks for all your posts guys im going to try and get some testing done to really figure out whats going on this week. could anyone post up where the entire testing procedures are for the P0401 code or the FSM in general. im at work so i have limited time to surf for LC stuff sadly! Thanks!

 

[kerrye]

The link I put above explains how to test everything but it doesn't follow all the FSM methods. It does test all the components though. I think it's simpler because it uses mostly vacuum to test things. Definitely no need to remove the intake to test the VSV and no need to extend the wires to replace it with a more accessible cheaper dorman 911-850 VSV. You should be able to test all the components in less than half an hour or so with a Mity Vac.

 

[DHwreckage]

The link I put above explains how to test everything but it doesn't follow all the FSM methods. It does test all the components though. I think it's simpler because it uses mostly vacuum to test things. Definitely no need to remove the intake to test the VSV and no need to extend the wires to replace it with a more accessible cheaper dorman 911-850 VSV. You should be able to test all the components in less than half an hour or so with a Mity Vac.

guess ill have to go buy one

 

[mod5csi]

Dont bang your head. You dont need a mighty-vac. And even if you did you can rent them from most parts stores. I used a vacuum gauge with a T, and used the suck and pinch method as outlined by snake eater.

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

And looking at kerrye's write up he linked, that is a pretty good way to go about it. Still dont NEED a mighty vac, but they are handy and you will probably ingest fewer hydrocarbons that way.

 

[kerrye]

you're right. You don't really need a mity vac, just a vacuum gauge and some lungs. But I've owned so many 123 Mercedes that I now look at a mity vac as an indispensable tool.

 

[DHwreckage]

i think ill be leaving work early and swing by orielly's and pick up a mighty vac or similar and see how the EGR is doing! thanks for the advice and links if you think of anything else dont hesitate to tell me, on a side note also contacted powderpig incase im too noob to fix this junk! oh and here are my emissions results

 

[DHwreckage]

picked up a mighty vac yesterday for 40 bucks so i couldn't say no. hopefully ill get home with enough light left to start testing the EGR will update when i find something!

 

[TrickyT]

There's a way to replace the VSV solenoid without getting under the intake. Basically involves longer wires and hoses and attaching a new VSV outside that area.

Replacing the VSV doesn't require splicing in longer wires nor do you have to remove the intake chamber. But you do need a series of long 3/8" extensions for your ratchet. Search for a thread using keywords "EGR VSV long extension" or something like that. It has pictures and tells how to make the job easy-peasy.

 

[ChiTown]

You're better off pulling the upper when you do the vsv. I cleaned a ton of carbon out of the metal hard lines, the same carbon that clogs the vsv. Another good reason to pull it is so when you're cleaning out the big EGR port you don't knock all that junk into your engine. If you still need another reason, it's easier to replace all those old (probably cracking) vacuum lines.