Engine/Exhaust Refresh 1997 FZJ80

Joined
Sep 15, 2016
Messages
490
Location
Chattanooga, TN
This may help:


Basically the cats get really hot and anything in the exhaust air that is unburned, that can burn, will be combusted when it passes through the cats. This is mostly to catch unburned hydrocarbons I think and converts them to co2 and h20 which is better for the atmosphere :) If you are dumping too much crud into your exhaust stream from the engine it can build up on the inside of the cats and clog them or cause other issues. Raw oil/coolant/fuel could cause this basically. In some cases too much raw fuel can cause them to overheat I believe and then the material inside the cat can fracture and block itself up etc...

Easy things to check related to cat operating conditions in my opinion:
  1. is your fuel mileage in a normal range? if it's way low you may be dumping raw fuel into the exhaust essentially, if your mileage is too high you could be running lean and have overheating risks which is a separate topic...
  2. are you consuming oil between oil changes? A small amount (less than half a quart maybe?) could be acceptable between 6k oil changes but I'd want less than that. My 250k 80 needs no oil between 6k mile oil changes for instance. Of course leaks outside the engine factor in here as well.
  3. are you needing to add coolant to the cooling system beyond a small amount annually to cover evaporation? You don't want to be passing coolant into the exhaust for a lot of reasons. Same for leaking it externally.
If you dive into any work PM me and I can pass along my old parts lists. They will need review/revision but would be a help getting started at least.
 

baldilocks

Battle Ground, WA
GOLD Star
Joined
Jan 29, 2014
Messages
5,880
Location
Battle Ground
 
Any thoughts on how I got the clogged cats? I'm no wizard when it comes to this stuff. I have an FSM, can read, can count to ten, and I'm reasonably handy with tools - but I'm self-taught when it comes to vehicles.
I’m not a certified automotive technician either but it would seem to me that the engine was running rich for a long time, the cats died and stopped heating up. How did you know the cats were blocked? How badly were they blocked?? My cats have 300k on them. I just had the exhaust system off and the cats looked new inside so back on they went.
 
Last edited:
Joined
Nov 9, 2012
Messages
8,803
Location
Olathe, KS, USA
 
When vehicles are not driven distances regularly to fully heat them up to completely burn off the crud, then they clog.

Also, running lower octane fuels or from less reputable fuel suppliers, you may have more contaminants that overload the emissions systems.
Below is a post with all the part numbers you can use to "design" your exhaust system and gather prices. I forgot to include the nuts and gaskets for the O2 sensors.


 
Joined
Apr 17, 2018
Messages
143
Location
Pensacola, FL
This may help:


Basically the cats get really hot and anything in the exhaust air that is unburned, that can burn, will be combusted when it passes through the cats. This is mostly to catch unburned hydrocarbons I think and converts them to co2 and h20 which is better for the atmosphere :) If you are dumping too much crud into your exhaust stream from the engine it can build up on the inside of the cats and clog them or cause other issues. Raw oil/coolant/fuel could cause this basically. In some cases too much raw fuel can cause them to overheat I believe and then the material inside the cat can fracture and block itself up etc...

Easy things to check related to cat operating conditions in my opinion:
  1. is your fuel mileage in a normal range? if it's way low you may be dumping raw fuel into the exhaust essentially, if your mileage is too high you could be running lean and have overheating risks which is a separate topic...
  2. are you consuming oil between oil changes? A small amount (less than half a quart maybe?) could be acceptable between 6k oil changes but I'd want less than that. My 250k 80 needs no oil between 6k mile oil changes for instance. Of course leaks outside the engine factor in here as well.
  3. are you needing to add coolant to the cooling system beyond a small amount annually to cover evaporation? You don't want to be passing coolant into the exhaust for a lot of reasons. Same for leaking it externally.
If you dive into any work PM me and I can pass along my old parts lists. They will need review/revision but would be a help getting started at least.
Wow, thanks for the info! I'll take a closer look and see if I can reason my way through what's going on.
 
Joined
Apr 17, 2018
Messages
143
Location
Pensacola, FL
I’m not a certified automotive technician either but it would seem to me that the engine was running rich for a long time, the cats died and stopped heating up. His did you know the cats were blocked? How badly were they blocked?? My cats have 300k on them. I just had the exhaust system off and the cats looked new inside so back on they went.
How did I know they were blocked? Lol - because I started having serious power loss at random times, then I removed the upstream O2 sensor to test that theory and it ran fine. So out came the sawzall and I cut them out. Held them up to the light once they were out and it was darker than night. No light passing through whatsoever. So I don't know if they just clogged up completely or if some of that catalyst broke loose and blocked the flow but whatever it was the cats were trashed.
 
Joined
Apr 17, 2018
Messages
143
Location
Pensacola, FL
Like I said, I have a P0401 code which I know relates to the EGR system but most of what I read on that seemed like the code had more to do with blockages in the plenum EGR passages. But would a bad EGR system lead to clogged cats just from "dirtier" exhaust?
 
Joined
Sep 15, 2016
Messages
490
Location
Chattanooga, TN
But would a bad EGR system lead to clogged cats just from "dirtier" exhaust?
Not to my understanding, no a non-functioning/disabled EGR system wouldn't clog cats or cause many issues with these engines. In some scenarios you will have different combustion temps and emissions profiles from what I understand but no noticeable issues or perf. differences without EGR.

Also, P0401 can relate to clogged passages in the manifold and throttle body, vacuum leaks and problems with other components in the system like the EGR Vacuum Modulator, EGR Valve, EGR VSV valve under the intake and some other less-common failure points. It's pretty easy to troubleshoot the system once you figure out how it all works together. Since many Toyota's and other vehicles have similar systems you can find some good troubleshooting vids on youtube and a lot of good info on this forum to start figuring that system out. You can also just replace/repair it all but you may still end up needing to troubleshoot it after that to find the part you missed ;). I'd always start with replacing the EGR vacuum modulator as it seems to lead to system contamination and clogged/ports etc. There's a good test for it in the manual and checking the filter for excess grime/contamination is also a good check for it.
 
Joined
Apr 17, 2018
Messages
143
Location
Pensacola, FL
Not to my understanding, no a non-functioning/disabled EGR system wouldn't clog cats or cause many issues with these engines. In some scenarios you will have different combustion temps and emissions profiles from what I understand but no noticeable issues or perf. differences without EGR.

Also, P0401 can relate to clogged passages in the manifold and throttle body, vacuum leaks and problems with other components in the system like the EGR Vacuum Modulator, EGR Valve, EGR VSV valve under the intake and some other less-common failure points. It's pretty easy to troubleshoot the system once you figure out how it all works together. Since many Toyota's and other vehicles have similar systems you can find some good troubleshooting vids on youtube and a lot of good info on this forum to start figuring that system out. You can also just replace/repair it all but you may still end up needing to troubleshoot it after that to find the part you missed ;). I'd always start with replacing the EGR vacuum modulator as it seems to lead to system contamination and clogged/ports etc. There's a good test for it in the manual and checking the filter for excess grime/contamination is also a good check for it.
I had checked it before to see if it was clogged but I may have missed something. I'm more concerned about the exhaust leaks and cooling system than anything else. The more I can fix the better but money is a factor as well so I'm weighing my options as well as long term plans before pulling anything apart. The vehicle runs just fine minus the exhaust leaks so I don't want to ruin something in the name of PM just because I rushed a decision.
 
Joined
Apr 17, 2018
Messages
143
Location
Pensacola, FL
When I get home I'll post up some pictures of the engine bay and point out what I think the issues are. That way if I'm making some wild predictions yall can rein me back in haha
 
Joined
Apr 17, 2018
Messages
143
Location
Pensacola, FL
20200406_155534.jpg

Here you can see the valve cover gasket leak. It's not bad but there's clearly some oil seepage. And like I said, my throttle cable is toast. Still works but replacement is way past due.
 
Joined
Apr 17, 2018
Messages
143
Location
Pensacola, FL
20200406_155545.jpg

I realized I'm missing the clamps for the PCV hose. You can see the dark pillars residue from where there's not a good seal. You can also clearly see that I have some sort of leak at the throttle body. Several dry rotted hoses as well. This is why I want to refresh the whole top end - or at least most of it.
 
Joined
Apr 17, 2018
Messages
143
Location
Pensacola, FL
20200406_155554.jpg


Another minor issue is the leaking PS reservoir. No steering issues, just always seems that there's a sheen on the res from seeping fluid.
 
Joined
Apr 17, 2018
Messages
143
Location
Pensacola, FL
20200406_155718.jpg

Driver's side view. I've also had some gas tank pressure which I've read is related to a bad charcoal canister. Not sure which way to go on that one: new vs aftermarket vs refill.
 
Joined
Sep 15, 2016
Messages
490
Location
Chattanooga, TN
Limited info to go on but from what I see in the pictures the heater valve on the firewall and the radiator would be high priority for replacement. You also do seem to have some relevant levels of corrosion :(

You are on the right track and there's no doubt you have a lot of PM and baselining work ahead of you which is pretty much the rule with a truck this age, except for cases where it's been done already. Some repair tasks are probably high priority, and possibly urgent right now, while others can wait until the high priorities are addressed. You're going to be in the planning and information/parts gathering phase for at least a little while and while mud has all of the information you need only you can inspect your truck and create an execution plan (unless you hire it all out of course).

I recommend you start a digital list in a spreadsheet or similar that can be edited and organized as it evolves. You can list out all of the currently known needed repairs/maintenance that you find as you review the 80 and read here on mud. Once you get a solid list and you've at least checked the common problem areas you can prioritize the tasks and organize into groups them for execution. Give items that can leave you stranded or lead to catastrophic damage/failure a higher priority. Group tasks that need to be implemented together. Then you can start creating separate parts lists and documentation (like links to related mud threads, youtube vids) for each task and start ordering parts for the initial tasks. As you move through the repairs you'll ID more items that need attention, you'll learn more on mud, etc. and the lists will evolve. The more of this planning you knock out now though the more effective your time/$ efforts will be and the less likely you are to have to redo things later, get stuck in-process without parts or end up stranded because you fixed the wrong items. If you want to follow this approach and don't know where to start pm me your email and I can setup a template spreadsheet for you in the next few days based on what I've done the last few years on my 80 project.

You may just need to focus on urgent tasks ahead of your move and wait on items like oil leaks/etc. until later unless you have a good bit of time/$ to throw at this now or can hire it out to a pretty fast wrench.

Hope that's helpful... Not everyone approaches 80 work like I describe above and you can also follow different approaches and end up in a good spot. If you want yours to be a solid 80 the work needed to get there will be the same no matter how you go about it and you'll be following a path that many/most of us here have tread before so you'll have lots of clues and help along the way.
 
Top Bottom