EGR is going to be the death of me...save me! (1 Viewer)

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In short, I have a fabulous 96 LX that is throwing the EGR code. It also doesn't help that I must go through emissions testing. Through the several searches I have achieved the following; HOWEVER the code remains....

-EGR tests out
-Modulator tests out
-VSV works
-intake port is spotless
-temp sensor tests out and is clean

Next..vacuum lines, but I'm nervous that these may have no bearing on the code.

With that, am I missing something? Open to anything you all have to share. I'm at a loss. The check engine light doesn't bother me, but not passing emissions does.

Would the resistor mod be worth it? If so, what do I need to do? I've seen various resistor ratings.

Thanks Mud!
 
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VSV for EGR works? You measured/tested it on the bench or insitu? There's a bucket load of vacuum lines under the intake manifold that would be worth looking at. You pulled off the throttle body to check build up of carbon and crud in that area of the intake manifold?

So, you reset the EGR code via OBD2, how long till it reappears?

cheers,
george.
 

b16

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Make sure you can blow through the ports on the throttle body. I had this problem, and once I cleared it out my Modulator then failed in a way that wasn't really described in the test since port P was completely blocked on its own.
 
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VSV for EGR works? You measured/tested it on the bench or insitu? There's a bucket load of vacuum lines under the intake manifold that would be worth looking at. You pulled off the throttle body to check build up of carbon and crud in that area of the intake manifold?

So, you reset the EGR code via OBD2, how long till it reappears?

cheers,
george.
George, thanks for the reply. I have been the one working on his truck hoping to get the issue resolved. To answer your questions:

VSV was tested installed in the vehicle. Resistance checked as well as applying 12v gave the expected result of not allowing air to pass throught.

I did pull off the throttle body and the egr port was unobstructed.

I swapped the egr temp sensor from his truck with mine to check it. The resistance I got on it was quite a bit higher than mine. No change.

Code seems to return after a couple of drive cycles.

Kevin
 
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Code returning in a couple of cycles is common, since after clearing it takes a few drive cycles/profiles for the error to be flagged, so imho I'd say you have a hard failure versus an intermittent which I've seen (CEL comes and goes - eventually stays on 100%).

Often it is the EGR VSV that fails or acts up - especially since it is in a quite hot area of the vehicle. May pass while cold then stick/fail while hot. Of course lots of other areas can cause a fail. You could try the 'external' VSV hack where you get a cheap aftermarket VSV and connect it up on the outside of the intake - near the transmission dipstick area.

Lots of vacuum lines, one could be clogged or leaking. There's a menagerie of them under the intake manifold along with lots of little hardlines. I replaced all my vac lines when I had the intake off fixing a dead injector, cheap future insurance. Good time to replace the fuel filter too. Of course there's a lot of make work projects if you get to the stage of removing the top intake manifold :)

Did you follow the FSM steps for testing the EGR system, they are quite comprehensive?

For expedient smog test if it's coming down the wire, the resistor solution is likely a good idea.

cheers,
george.
 
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Thanks again. I think replacing the vacuum lines will be the next step since it probably needs them anyway. Also, good thought on the VSV acting up when hot. The VSV hack may be worth while to do while doing the vacuum lines.
 

Rivman1243

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I've been in the same boat and here's what I found on my engine. The vsv was bad, the port through the intake was plugged, the ports in the throttle body were plugged, the egr vacuum modulator was plugged with rust, and lastly the vacuum lines under the manifold were toast.

The egr valve tested good and still does. So I replaced the vsv, all the vacuum lines, the vacuum modulator, cleaned the port through the intake, cleaned the throttle body ports and throttle body, cleaned the egr port in the intake. This worked great for a month. Then the check engine light came back. P0401!

Currently the egr valve is letting rust dust into the vacuum modulator. I kept blowing it out but it keeps plugging up. So I installed a little inline vacuum filter I stole from my dad's spare Mercedes diesel engine. 3 weeks and no light!
HTH
 

Rivman1243

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Also the egr codes runs on a 2 trip logic system. I.E. It takes two separate "trips" where the egr system failed to turn on the light. It will log a pending code the first time it fails.
 
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Open to more info on the resistor mod. Feel free to chime in or PM. This may be the angle I'll need to approach. Appreciate the feedback from everyone.
 
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Thanks for all the help! We got some time to work on it today. So far, no P0401 code.

We replaced all the vacuum lines to the EGR and VSV, also we replaced the VSV with the Dorman one. With the old VSV off and 12v applied I could just barely hear the slightest bit of air coming through it. Hopefully in the next few days he can get it through emissions and get it back on the road.
 
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A-men! This code was a booger to say the least. Many thanks to Kevin (Monty231) and Mud!! Of course it had to be the last thing we thought it truly was.
 
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Tried to blow through both throttle body EGR vac ports and the both appear plugged. How in the $@&" did you clear those out? Where is the other end?

Port 'R' is plugged.
 
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Thanks. I was able to make some progress with some shop air. Hopefully this fixes my p0401. (Was a p0402 before I unplugged the manifold port). Doh.
 
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Sorry for the late response----mine were dirty, but cleaned out fairly well with carb cleaner.

Cel came back. Cleared them one more time before I grab some resistors. #FingersCrossed
 

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