deanbrown

BEFORE reading this, keep an eye on this thread:

https://www.clublexus.com/forums/ls4...now-p0401.html

I got a P0401 EGR Insufficient Flow dtc, which sort of makes sense.

[End edit]


This procedure was performed on a 1996 LS400 with 250K miles. I have observed outstanding results for the sound of my 96 LS400, which has 250K miles.

Some notes at the end of this document explain what the EGR does and why it can be removed.



Before today, and for the last 3 years, the engine of my 96 LS has sounded like a 1975 Ford Cortina on a cold engine going up a steep hill – valve train cha cha cha cha cha cha cha – a truly worrying noise! After this morning, it sounds like my 99 LS with 85K. And that ain’t no BS, the difference is remarkable.

This was a very very simple procedure – 2 hours max. (To put this into perspective, it took me 11 days to change my TB/WP/Cam/Crank seals). I had the bottom half of the tube off in 10 minutes.

The EGR tube is mounted opposite the first oxygen sensor, on the exhaust pipe just before the first passenger side cat. The pipe was broken right through on the concertina section. The other end of the pipe enters the back of the engine somewhere between the firewall and the intake – to me completely impossible to reach.

The fix is summarized as follows: Undo the bottom half of the pipe, which can just be reached, (its flange is attached to the exhaust pipe), and blank it off. The other part cannot be removed, but can be shut off by screwing in a large bolt. Since it is only under a slight vacuum, as far as I am concerned it is closed for good.

Here is what a new pipe looks like. I did not use this, because I could not reach the upper flange where it enters the back of the engine. (This is just so you can see what it looks like. I would be happy to sell this, if anyone really wants it.)

deanbrown

In this next picture I have actually removed the flange, but I put the nut back on to show how little room there is. The only thing that I could get on the nut was a ¼” drive 12mm socket with a ¼” breaker bar. I could not use 3/8” sizes - no room. I don’t use 12-point wrenches on exhaust bolts, but you can choose that if you want to try.

deanbrown

The nut came off with two-hand force, though it was a struggle. The nut has been on there for ¼ million miles.

The second nut, about 2 inches higher, would not come off with this same effort - I could not undo it with the breaker bar. You might be more lucky. I had to use my new toys from snap-on:

deanbrown

In order from bottom right, this is all 3/8” and includes breaker bar, extension, snap-on FZ1 extension connector, 1-1/2” wobbler extension, another FZ1, and a 12mm 3/8” socket. I only used the FZ1’s because I finally found a use for them. You could probably get away with using just the ¼” breaker bar as above, by putting a ring wrench on the end and turning it with another wrench at the bottom. (Those FZ1’s are $20 each).

deanbrown

Here it is installed on the top nut:

deanbrown

After 10 minutes:

deanbrown

Cut the flange off the old pipe, leaving 1/2" of pipe, and make a gasket to blank off the opening: I used a couple of layers of galvanized steel sheet – the sort used in air conditioning ducts:

deanbrown

Put it next to the old gasket. Drill out the two bolt holes after matching up for size.

deanbrown

I also wrapped this with stainless steel tape, simply because I just happened to have a roll of the stuff, to make it a bit more corrosion resistant.

deanbrown

And here it is installed and bolted down:

deanbrown

For the other end of the pipe, which is remaining on the engine, there was just a gaping open tube, with part of the concertina at the opening. To seal this, I found a large allen bolt and threaded it into the opening and in as far as it would go. Bolts like this have a nice rounded corner at the end of the thread, which should seal nicely with the narrower straight section of the old pipe.

Test the bolt on the removed section, as here:

deanbrown

And then install it onto the engine side, as shown:

deanbrown

(BTW to take this pic I had to push the camera up into the hole above the cat, and hope for the best. It is not as accessible as this looks!)

The bolt I used was the perfect size – the outside thread is around 15 to 16mm diameter – the bolt slips between the opening of a 16mm wrench, but not a 15mm.

I didn’t think of this at the time, but it might make sense to use thread blocker on that bolt, but I’m not concerned about it.

The vehicle now sounds like a real lexus, and not a junker with valve train troubles.

Test drive!

Notes:

EGR (Exhaust Gas Recirculation) is a method to dilute the oxygen coming into the combustion chamber to reduce the combustion temperature. This makes the engine run quieter and last longer. It also makes it less prone to detonation. (You could in theory inject any inert gas, such as nitrogen, but there is a never-ending supply of the stuff in the form of already-burned exhaust gas).

EGR is NOT meant to be used for cleaning the exhaust by giving it a second run through the combustion chamber. It is solely to reduce the combustion temperature. Only a few percent of the exhaust is actually recirculated.

I have read in a few places now that the EGR pipe is not even used in Japanese cars. There are several threads on clublexus that describe blanking it off.

There was never any engine code from this gaping hole, which was open to fresh air for so long.

PureDrifter

iTrader: (10)

this is a decent stop-gap measure but I would definitely want to replace that EGR tube in the long run. EGR does reduce combustion temperatures, and the reason for this is to greatly reduce NOx output during combustion. For the USDM cats and the motor in general, I'd find the time to install the new EGR tube.

also, many/most japanese cars don't have EGR because simply it is expensive, and the japanese government doesnt require the same NOx levels.

dashan

Dean B,
A good job well done. Those two nuts are very difficult to take out, that's why I had to pay muffler shop to get them.
Do you have any check engine light on with plugging the pipe with the bolt?
Also very nice tool set.
Thanks