P0401 Defeated - with pics (1 Viewer)

[txgringo]

After reading this thread I decided it was time to take care of the P0401 that I've had since I bought this 80. Pulled the TB and upper intake, cleaned them with carb cleaner over and over and over until I had all the carbon buildup and sludge cleared out. Cleaned out all ports to ensure proper flow through the hoses. Replaced the VSV valve and all hoses connecting to the manifold and EGR components. Cleaned the EGR temp sensor as it had a fair amount of carbon buildup on it. I broke a vacuum nipple on the Bimetal Vacuum Switching Valve and so had to replace that also (I would strongly advise caution when touching this little turd as they are HARD to get to and I had to modify a deep socket to replace it).

While I had everything out of the way I also replaced the fuel filter, spark plugs and spark plug wires (which were all well overdue) as well as the PCV valve, grommet & hose and the other ventilation hose coming from the valve cover. Since I lost some coolant changing out the Bimetal Vacuum Switching Valve I also did a coolant flush instead of just topping it off.

While she runs WAY better now, the P0401 came back today . During the work listed above, I inspected the EGR valve as best I knew how and hosed it out with carb cleaner, but I'm suspecting that it may be the cause of the code resurgence.

I don't have any special tools test the EGR valve. Is there any shadetree approach to testing this, or should I just order a new one and be done with it? Anything else that I might have missed in this process or other things that I should be looking at? I was really looking forward to having this code sorted out, but have kind of hit the limit of my knowledge and patience at this point.

 

[LC4LIFE]

Shameless plug (no pun intended) here, but I would do this. Hundreds of these out in use....

1995-1997 FZJ80 EGR Temp Sensor Test Plug Kit

EGR, EGR delete, 97 Land Cruiser EGR, Land Cruiser P0401, P0402

huddexpo.com

 

[Qball]

After reading this thread I decided it was time to take care of the P0401 that I've had since I bought this 80. Pulled the TB and upper intake, cleaned them with carb cleaner over and over and over until I had all the carbon buildup and sludge cleared out. Cleaned out all ports to ensure proper flow through the hoses. Replaced the VSV valve and all hoses connecting to the manifold and EGR components. Cleaned the EGR temp sensor as it had a fair amount of carbon buildup on it. I broke a vacuum nipple on the Bimetal Vacuum Switching Valve and so had to replace that also (I would strongly advise caution when touching this little turd as they are HARD to get to and I had to modify a deep socket to replace it).

While I had everything out of the way I also replaced the fuel filter, spark plugs and spark plug wires (which were all well overdue) as well as the PCV valve, grommet & hose and the other ventilation hose coming from the valve cover. Since I lost some coolant changing out the Bimetal Vacuum Switching Valve I also did a coolant flush instead of just topping it off.

While she runs WAY better now, the P0401 came back today . During the work listed above, I inspected the EGR valve as best I knew how and hosed it out with carb cleaner, but I'm suspecting that it may be the cause of the code resurgence.

I don't have any special tools test the EGR valve. Is there any shadetree approach to testing this, or should I just order a new one and be done with it? Anything else that I might have missed in this process or other things that I should be looking at? I was really looking forward to having this code sorted out, but have kind of hit the limit of my knowledge and patience at this point.

Did you replace the modulator? That fixed my 401.

 

[txgringo]

Did you replace the modulator? That fixed my 401.

I didn't replace it, but I did clean it out and made sure the ports were able to pass air. I didn't have any vacuum testing tools, so I just blew into each port. Might be worth trying a modulator just to rule it out. It's a lot cheaper and easier than the EGR valve. those kind of suck to work on...

 

[LC4LIFE]

I did solve the code on a previous 80 by replacing the modulator. I think the new ones have a blue top rather than green if I remember correctly.

 

[vegasfj40]

While the truck is idling pull the vacuum hose to the EGR valve and put vacuum to it. If the engine stalls then the valve is probably ok.

 

[vegasfj40]

I was able to cure my code by following the steps in the FSM. I actually had a couple of problems. Make sure the ports on the throttle body are clear. Also the pipe running through the upper intake.

 

[Qball]

I didn't replace it, but I did clean it out and made sure the ports were able to pass air. I didn't have any vacuum testing tools, so I just blew into each port. Might be worth trying a modulator just to rule it out. It's a lot cheaper and easier than the EGR valve. those kind of suck to work on...

Replace the modulator with OEM version pronto!

 

[txgringo]

Replace the modulator with OEM version pronto!

@Qball you nailed it. I pulled the EGR modulator from my other 80, installed it in this 80, cleared the code, and have put about 200 miles on it with no P0401! Kind of makes me wonder if I could have avoided this whole endeavor by just spending 5 minutes to replace this one part to begin with, but after seeing the nastiness that was clogging my intake I'm glad I got it all cleaned out.

 

[Ronny Grady]

1 banana question - I can’t get the intake plenum off, it’s stuck on the back. I removed 6 bolts, 2 nuts, and the threaded pipe coupler in the back. What’s stuck?

 

[Stecz]

I'm in the middle of this project, but I have a few questions.

The TB has 2 coolant hoses (not sure which is in and which is out), but there is a short one, and then the long one, is everyone replacing these hoses with the section of fuel injection hose? Or do I need to source the correct size of coolant hose?
Is there a trick to get to the long one that ends underneath the intake manifold?

Also, should I replace the fuel hose going into the filter? I figure that thing is 23 years old at this point. Does anyone have a part number?

 

[Ronny Grady]

Update - you need a t6 to remove the studs and pull the EGR valve, then the plenum came out no problem.

for what it’s worth: I replaced the coolant hose in & out of the TB with fuel hose. I didn’t replace my fuel hoses when changing my fuel filter.

 

[Stecz]

good call on the T6. I just finagled the EGR valve out instead, but that will be much easier on the way in.

I'm going to see how quickly I can get that high pressure line. I've lost an old car by fire due to a fuel line splitting after I messed with it.

 

[davidp14]

I believe The small TB hoses are available from wits end.

 

[Stecz]

Is there a trick for getting the TB cooling hose off? it's up underneath the intake manifold. I can barely touch it, let alone get pliers on the hose clamp to remove the hose clamp and pull the hose off.

Whoever decided to mount the fuel filter on the bottom of the intake manifold must hate the world. , But at least I got that off.

 

[BILT4ME]

Is there a trick for getting the TB cooling hose off? it's up underneath the intake manifold. I can barely touch it, let alone get pliers on the hose clamp to remove the hose clamp and pull the hose off.

Whoever decided to mount the fuel filter on the bottom of the intake manifold must hate the world. , But at least I got that off.

Do a search for "bypass hose #1" and you'll find an answer.

 

[Stecz]

I guess I should have tried through the wheelwell. That probably makes the fuel filter easier also.
thanks for the pointer.

 

[Stecz]

finally done, seems to run good, except now I have to replace the power brake vacuum line. It's cracked on the end where I removed it from the intake manifold.

My hints:
- bolts to get from underneath: 2 rear nuts and 1 long bolt, inner bolt for fuel filter
- remove the studs for the EGR valve to get it off easily
- remove the transmission dip stick tube to get to things easier
- get to the TB bypass hose through the wheel well

 

[Stecz]

I forgot one thing. I didn't tighten the EGR connection. What size fitting is that? My biggest wrench is 1 1/8" and it's bigger than that. I tried to use a crescent wrench to tighten, but it's too bulky.

 

[HardyDanger]

So, while I have the @LC4LIFE temp sensor kit on the way... I was just poking around between rainstorms trying to determine what my next moves are. I think I have a 14 months before another California Smog Sniffer, and my OBD2 says 4 of 7 at readiness, methinks I'll have to tackle this all at some point.

My Valve Cover gasket is weeping like my wife during a bad holiday hallmark movie, it seems like a perfect time to do that gasket too, is anything else to do "while I'm in there?" other than fuel filter/hoses? Plugs and wires are at 10K since last change.