Oh joy, P0401 is back... (and how 80's fail emissions)

[ToddD]

Paul... you don't happen to still have those O2 sensors sitting around, do ya?

I'm trying to pass emissions and have failed twice.
http://forum.ih8mud.com/80-series-tech/520570-failed-emissions-test.html

 

[Inukshuk]

My catalytic converter temperatures (1993) were 430 +/- 10 inlet and 530 +/- 10 outlet. I had just come off 15 minutes on I-70. 65 degree day, three blocks of local driving, shut it off for three or four minutes and then turned it back on and tested while idling, with AC on for some extra RPMs.

A Yahoo page said 100 degree rise is good. This in-depth paper says 200 - http://www.bearriverconverters.com/data/CatOpp.pdf This, from Toyota, wants 550 minimum for efficiency operation, with 750 as ideal - http://www.autoshop101.com/forms/h64.pdf Another interesting read - http://www.catalyticconverter.org/news/news_page.cfm?Key=catalytic_converter-&News=216

New O2 Sensors are on their way and I will retest emissions after that.

For future readers this is on a 1993 FZJ80 with a freshly rebuilt (all but the bottom end) engine. All readings but NOx are great. EGR system has been tested. VSV has been tested. Cats and O2 sensors came off a 170,000 mile 1994 truck.

 

[rover67]

those are the numbers I was getting on my 60 with 70k mile cats behind the v8. 450 or so to 550 or so...

I think they were working OKm but the folks at the emissions place convinced me to put new ones on. they were only 40 bucks each for me so I went for it. not suggesting the same for you.

 

[Inukshuk]

those are the numbers I was getting on my 60 with 70k mile cats behind the v8. 450 or so to 550 or so...

I think they were working OKm but the folks at the emissions place convinced me to put new ones on. they were only 40 bucks each for me so I went for it. not suggesting the same for you.

Cool to hear. Did your new cats do the trick?

I can get the Bosal cats for about $120 each and that will be what I do if the O2 sensors alone don't fix me.

 

[subzali]

Dan, did I hear something at the meeting about your cats being in parallel and not in series?

 

[Inukshuk]

Dan, did I hear something at the meeting about your cats being in parallel and not in series?

Yes they are. The exhaust merges after the cats. Both O2 sensors are in front.

 

[Inukshuk]

Passed Emissions!!

__________Test 1____Test 2_______Test 3
HC_______0.346______0.1889______0.3118
CO_______3.984______4.000_______9.649
CO2______867.6______706.0_______766.5
Nox______9.354______9.256_______3.024

Test 1: no special prep, short wait, idled at 2,000RPM
Test 2: ½ tank premium, two cans red HEET, tires at 50PSI, well warmed up, short wait, idled at 2,000RPM
Test 3: NEW O2 Sensors, ½ tank premium, tires at 50PSI, no HEET, 15 minute wait, idled at 3,000RPM

Tires were 285/75R16 Nitto Terra Graplers.

So, HEET brings down HC and CO2, seems to not affect CO or NOx, and bad O2 sensors affect NOx. As noted before, catalytic converters measured a 100 degree temperature rise so between that and this test they seem to be working fine.

Since I could not find it posted anywhere (here or MUD) ill searchably write bad O2 sensors cause high NOx readings. Lower NOx by getting new O2 sensors. I used Toyota OEM oxygen sensors.

Than you again Robbie for suggesting I test after replacing the O2 sensors and before changing catalytic converters. Heated 4-wire O2 Sensors as we have in our cruisers should have a 60,000 - 100,000 mile life.

 

[nuclearlemon]

crap...that time again.
anyone passed with massive amounts of leaks? i've got at least three exhaust leaks before you even hit the second cat at the muffler

 

[wesintl]

I'm going to start putting a reminder on my calendar to drive past the emission stations a month before hand so I don't need to go in.

I have 2 good cats you can weld in if needed.

 

[nuclearlemon]

thanks wes, but cats arent' the problem (at least i don't think so ). i've got one blow throw on the pipe where the front o2 sensor is and a couple leaks on the flex that i put in when i had to jerry rig a second cat last time. stupid emissions

 

[Inukshuk]

I have an extra set of 93-94 downpipes. One has a small hole that would be an easy weld patch. But if you have a front O2 sensor I think your rig is newer.

 

[powderpig]

I had a neighbor that passed with flying colors and has a big hole before the cat and muffler. No check engine light on, But the holes were after the O2 sensor. Early nissan pick up that is just beat to death. He called me up to brag and we both laughed.

 

[nuclearlemon]

no mention of the three exhaust leaks but failed on nox. gas cap too, but i was prepared for that and have a new oem cap on the seat. 02 sensors and cats are all within five years. only one cat is that old, the other is two years old (last time i had to test) and sensors are about 4 and 2 years old. less than fifty thousand miles on any one componant. cats are aftermarket magnaflows, sensors are oem. cats only show about 20 degrees difference from in to out. 377 range and 395+ range. guess it's cat time again

 

[Jacket]

Can't beat this! My 80 passed via roadside emissions this year.

 

[subzali]

Went down on Sunday to help my dad with some stuff. His driver's side mirror was broken, so I got that replaced with one off of the 'Mud classifieds. The heater fan had also ingested some mice, so had to get that cleaned out. He also said the CEL has been on for a while, so I tried to drive it around to get it to blow the code (had just reconnected the battery). Never blew the code, but he texted me last night and said the code is P0401. He's also getting a lot of fuel tank pressure, which I think is charcoal canister-related. Oh joy.

 

[coax]

I've often wondered if the EGR VSV valve going bad or not functioning properly can cause the fuel vapor from the tank not to be pulled out of the charcoal canister into the intake. Then the charcoal canister becomes super saturated and we end up with problems 200k miles later. I think the 401 code is insufficent flow, meaning the valve won't open and you won't get vacuum? And by extension no vacuum to vent the CC. I'm not familiar enough with the system but maybe others can chime in?

All I know is that my fuel venting problem was reduced (not eliminated) when Robbie fixed my EGR VSV issue. I suspect I'll need to replace the CC at some point as well. Don't forget to check the passageway through the intake for clogging.

 

[subzali]

Yep, I immediately thought the same thing. I have not done any research on how the system works though.

 

[nakman]

Look back to post #26 in this thread..

 

[subzali]

Look back to post #26 in this thread..

Yeah I don't think that's an option because my dad just spent beaucoup $$ for new exhaust and cats that burned out because he had a CEL on. I think he'd rather get the problem fixed.

 

[corsair23]

When the VSV on the 80 went south, I didn't want to deal with it so I took the 80 to Ben

He has tricks to getting to stuff in impossible locations, like the VSV, without dismantling 1/2 of the engine. Might be worth a PM to him to learn the trick if you are planning to tackle this on your own like I imagine you are. As I recall it had to do with LONG ratchet extensions coming up from below but beyond that I was just happy with the cost and that it was fixed...