EGR hose blows off - plugged catalytic convertors?

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Phil H

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While running some errands on the weeked, while getting on the off ramp getting off the freeway, heard a hissing sound startup under the hood near the firewall accompanied by slight loss in power. Pulled over and found the vac hose that connect to the lower port of the EGR to the EGR Vacuum Modulator had come off and was venting exhaust gas!

After cooling down, put it back on to get home and it did it again on the offramp nr home. No CEL codes thrown during either time.

I started ging thru the OEM manual and my notes on the last time i replaced the EGR, Modulator and VSV -- was back in '05 and ~ 50k mi ago -- and did the EGR tests on the truck. With engine cold, and at idle, and a hand vacuum pump on one side of the T (and the other side of the T blocked off), I was able to pump a sm amt of vac and get the EGR to close, causing the engine to stumble. I think the EGR is ok. Was able to do this several times to convince myself: apply vac to the T, get the engine to stumble and then release; repeat.

EGR Vacuum Modulator appears ok too. Pulled the cap and looked at the foam filters - some dust but clean and no burn marks. Vacuum seems to pass with a bit of restriction. No burn damage as others have mentioned. I did pull over quickly and may have avoided destroying it.

VSV is hard to get w/o pulling intake apart so could not check that and listen for the solenoid to click.

And, again, CEL codes!

What's bugging me is the exhaust gas coming out that lower vac port at idle even when cold -- its coming out all the time! Looking at diagram on pg EG-114 in oem manual, that lower port on the EGR IS shown to be connected to the exhaust. I never checked this port before so dont know if this is 'normal'. That diagram for the lower vac port on the EGR sure indicates that exh CAN come out. IS THIS NORMAL?

Scouring MUD over past couple of days - found these threads:

https://forum.ih8mud.com/80-series-tech/427493-egr-valve-aka-blowtorch.html

https://forum.ih8mud.com/80-series-tech/363575-p0401-defeated-pics.html

https://forum.ih8mud.com/80-series-tech/399227-loss-power.html

https://forum.ih8mud.com/80-series-tech/28195-unhappy-80-cat.html

P0401 Defeated - with pics link has some great pictures of the intake the plugged EGR port -- I did clean my intake and all the ports when i did the HG in '07 or so but they could be plugged. Would that cause the lower EGR port to vent exhaust tho?

I just pulled the rear catalytic convertor out - it was the easiest to remove of the two - to see if it was plugged. When I hold up to the sky, it looks like ~ 60% of the square holes in the cat are plugged. With the rear cat removed. started up the engine - still cold and at idle - and there was still exhaust gas coming out that lower EGR port when i removed the hose. It may be coming out at a slightly lower pressure but hard to tell. I would have expected to see almost no exh coming out the port with the one cat removed IF the cat was plugged. But, the front cat could still be plugged even more - no easy way to tell.

Replacing the cat's in CA does not look to be easy nor cheap. OEM's from CDan are just under $2k for the pair. And the EGR SEEMS to be working. Throwing parts at this to troubleshoot will be expensive. The EGR is not that old either. I have had the 80 since new and this is the 2nd EGR I believe - maybe the 3rd (still looking for my repair notes from the HG.)

Anyone noticed with a well-running 80, does the exhaust always come out that EGR lower port at all times??

Appreciate any ideas. Thanks in advance!
 
Could you tell if the cat was plugged with carbon or was it melted? Got a photo?
 
I did take pictures but will need to download them when I get home again. Its hard to get a good picture of the matrix - held the cat to the sky and took a pic but the ambient makes it hard to get the DOF... I will post later.

Rear Cat: What I observed, tho, in the rear cat was all dried stuff. Nothing looked melted from either end. Looked like a honecombe with dry powder in the holes where 40% of them would pass day light.

Front Cat: did not remove it since its welded to the Y pipe and a lot work to get the entire Y out. But, w flashlight, saw the same thing. BUT, its like look in a dark cave - cant tell if the matrix is plugged or not withou some back light! Just thot about it - should have pulled the O2 sensor out and shined a light in that way!! In any event, it was dry and showed no melting.

Is the melting a sign of cat overheat and then a failure of the matrix?
 
Failure of the matrix; I remember that movie.

Melted catalyst is a sure sign of engine problems, as large amounts of unburnt fuel has been allowed to make it to the catalyst where it ignites and raises temperatures significantly. If they are plugged with carbon, that could also potentially be a sign of engine issues like excessive oil consumption, weak combustion, misfire, etc.

I work for an engine manufacturer, so I deal with catalytic converters every day. However, my experience with FJ80 catalysts specifically is pretty limited. With that said, if the 2nd cat was 60% plugged, you have a problem.

Dan
 
Here is the pictures of my rear catalytic convertor, removed from the 80 and held up to the sky with a little bit of extra light from a flash light:

Exit or rear of the Rear cat is the 1st pic

Entrance to the Rear cat is the 2nd pic.

HTH's - carbon blockage is there but not sure its enough to cause enuf back pressure to blow off the EGR to EGR Modulator vac line! But, maybe it is -- anyone experience this before and able to lay the cause at partially or half blocked cat?? At $2k for the pair its an expensive fix. BUt if that is what it takes to get the 80 back on the road for the wife....

Thanks!
Rear Cat - Exit - Med Res - L1090326.webp
Rear Cat - Entrance - Med Res - L1090329.webp
 
Yes it is normal for exhaust gas to be present in that line. It's purpose is to supply exhaust gas to the EGR Vacuum Modulator, which uses the exhaust pressure to control the strength of the vacuum signal to the EGR valve.

It could be possible that the hose is just old and loose, and not providing enough tension to stay on.
 
That's quite a bit of blockage, and it appears to be lube oil ash, rather that HC build up. How's your oil consumption? If it's light lube oil ash, you can *gently* blow compressed air at the downstream side and use a shop vac on the upstream side and remove a good portion of it.

Dan
 
Has anyone washed a catalytic convertor using water and a detergent of some sort? IDK
 
In general, detergents are a very bad idea for a catalyst, as they contain many elements that are poisonous to a catalyst like phosphates and or sulfates. Tap water contains minerals that can also poison a catalyst, so washing is not recommended.

Dan
 
TYM4FUN -- Thanks for confirming that. That helps a lot.

I finally got a chance to talk w my neighbor that owns a pr of auto repair facilities. He said the same thing you did and said he had had a number of Camry's come through w a similar EGR setup and hoses blown off and found that it was due to aging EGR 'vac' line. Now, he did point out that the particular pc of vac hose - btwn EGR lower poort and EGV Vacuum Modulator - is special, much thicker wall and he thot made from a silicone rubber and not a butyl rubber to handle increased temps and pressure. he suggested same thing - try a new hose first - even tho mine was replaced in '08 and ~ 50k mi ago. So, I ordered one.

Danimal92sport -- as to oil consumption, nothing that I notice at regular oil change intervals. I have run Mobil 1 almost since it was new. Change it every 5k to 7500mi depending on life's circumstances. Never noticed a drop in level when I check. May have to check more often as I get close to an oil change and see.

Lube oil ash -- that's good to know and will try blowing it out this afternoon. (Ordered all the gaskets and EGR hose - just getting in today.) Is there a normal amount of plugging due to ash that comes from age, use and time? In other words, these cat's are original - so after 15 yrs of use, is it expected to see some sig amount of accumulation in those sq passages?

I never noticed a large power loss nor high EGT temps either -- maybe too slow of a loss to notice. I have had a TRD SC and EGT for a long time and do pay attention especially when towing in the mountains.

Ill try a new EGR hose and clean what I can and post the results later. Thanks for the feedback!
 
Sure thing, hope it works out.
 
Phil H said:
Is there a normal amount of plugging due to ash that comes from age, use and time? In other words, these cat's are original - so after 15 yrs of use, is it expected to see some sig amount of accumulation in those sq passages?
Click to expand...

Yes, it's normal to some extent. I don't have enough 1FZ experience to really say how much is normal, though.
 
Its an '97 40th with ~ 170k miles with original cats.
 
Followup --

My parts arrived and so pulled the REAR cat out again. It took about an hour with compressed air and difference nozzles blowing from one side and then catching the debris and dust w a shop vac on the other end. It did clear most of the matrix, tho it still has ~ 10% blockage.

Installed a new EGR vac hose - the larger thicker one that connects EGR to EGR Vac Modulator - and the one that kept blowing off during de-acceleration.
Installed new exh-cat gaskets. After a 15 mi trip, all seems fine. Will watch temps and gas mileage to see if there is any performance improvement in the next day or so.

I have some pics of the REAR cat after cleaning - will post later.
 
TYM4FUN said:
Yes it is normal for exhaust gas to be present in that line. It's purpose is to supply exhaust gas to the EGR Vacuum Modulator, which uses the exhaust pressure to control the strength of the vacuum signal to the EGR valve.

It could be possible that the hose is just old and loose, and not providing enough tension to stay on.
Click to expand...

I'm not sure if I understood this statement correctly. From what i understand, NONE of the soft rubber hoses should have exhaust gas flow. These are vacuum hoses for opening/closing the EGR modulator. The vacuum in these hoses come from the VSV under the intake manifold. Only the hard metal pipe should have exhaust flow to the EGR valve.

Were you referring to a different hose? :hhmm:
 
Take a look at the OEM manual -- Looking at diagram on pg EG-114 in oem manual, that lower port on the EGR IS shown to be connected to the exhaust -- it confused me as well! Exhaust on what looks like a sm vacuum line?!? From here and the neighbor that owns the pr of repair shops, exhaust IS traveling thru that line at all times. The EGR Vacuum Modulator is using or sensing that to modulate the 'control' vac to the top of the EGR at the 'T'.

A closer look at the EGR vac hose, tho, revealls that its not the typical vac hose -- its got a thicke wall and does seem to be made from a differnent materical (silocone rubber vs butyl?). And, Toyota sources that one pc of hose as a seperate p/n vs the lenghts of thinner-walled vac line that u use on the rest of the EGR system.
 
alia176 said:
I'm not sure if I understood this statement correctly. From what i understand, NONE of the soft rubber hoses should have exhaust gas flow. These are vacuum hoses for opening/closing the EGR modulator. The vacuum in these hoses come from the VSV under the intake manifold. Only the hard metal pipe should have exhaust flow to the EGR valve.

Were you referring to a different hose? :hhmm:
Click to expand...

Nope, didn't say it was a common vacuum line. I was referring to the hose that travels from the bottom of the EGR Vacuum Modulator to the EGR hard pipe that the OP questioned. It is a much sturdier type of hose.

:)

Here is a very good link I just found to help you guys out. It has a great diagram, and an explanation of a generic Toyota EGR system.
http://www.autoshop101.com/forms/h61.pdf
 
Ahh, got it. Thanks for the clarification.
 
EGR hose blew off again while my wife was driving the 80!

This time, the whine from the super charger as I drove it around the block and the performance loss I was feeling in teh truck, made me suspect the front cat was plugged.

Pulled the Y pipe out today and found it was - could not see through it. Heard some debris rattling around as well. Using the shop vac and compressed air again worked to clean what I could reach. Then, pcs of the matrix on the upstream side began to break off -- some of them looked worn away. None of the pcs showed plugged passages, tho. Worked to get all the loose stuff out but was carefull not do anymore damage. Needed the truck to run when I was done without throwing a code.

Took an hourt to get the loose stuff out. Even w a decent LED flashlight, was still hard to see light pass thru the matix! It is hard to get a good look tho - the Y pipe bends and the small hole for the O2 sensor and EGT temp sensor dont really help. I CAN see some light pass thru - just not much. Put it back together tonite and drove it -- its driveable now -- no SC whine and performance is back and no EGR hose removal so far...

Maybe I am stuck and will have to replace the cats -- just hate the thot of spending so much $ to get CA legal cats.
 
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