'94 FZJ80 Failed Emissions (1 Viewer)

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My wife took our 1994 Cruiser for emissions and it failed today. NOX was 6.02, limit is 4.0. Two years ago it just squeaked by with 3.9 NOX after I rebuilt the EGR system, replaced VSV and a bunch of vacuum lines.

I just replaced the air flow sensor with a rebuilt unit from Cardone after it was throwing codes 2 and 8. The codes would return almost immediately after a computer reset. I reset the computer after the new VAF was installed and the codes haven't come back. It has had five drive cycles since the computer was reset.

I don't have any codes indicating bad O2 sensors, but I'm not sure how to check them.

CO is higher than it was at the last emissions check.

So, do I still need to do more drive cycles before the computer re-learns? Do I need new catalytic converters? O2 Sensors? Just get it good and warm and put some Heet in the tank and re-test?

I'm not opposed to new parts, but I don't want to just throw cash at it. What to do?
 
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I'm not sure 5 is enough cycles. I was doing a dozen when i fought that battle last.

if you have 20-year-old o2 sensors that might be the issue. More drive cycles first, though, because - and this is the part that really sucks about 93/94 and i feel your pain - the 93/94 o2 sensors are different, and only used on these trucks for those years, and thus very expensive for the exact working part, which is denso or denso by way of toyota. Bosch is right out. A couple people have said NGK worked but they don't talk about whether they kept working for a long time. I have 2 years on my genuine Yota replacements with no issues.

since you're not throwing o2 sensor related codes, we can hope it's not the o2 sensors. a bit.

When did you last do the basic tuneup stuff? Plugs, wires, cap, rotor. You want NGK or Denso plugs that you can get anywhere (both are OE, sometimes both on the same engine from the factory). OEM cap & rotor from the dealership are surprisingly cheap considering how much everything else on our trucks costs. I have 2 years on a $50 set of NGK wires with no complaints. OEM wires are Yazaki and cost more than a benjamin.

These ones: http://www.amazon.com/dp/B000CJ8D7Q/?tag=ihco-20
 
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Joined
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I'm not sure 5 is enough cycles. I was doing a dozen when i fought that battle last.

if you have 20-year-old o2 sensors that might be the issue. More drive cycles first, though, because - and this is the part that really sucks about 93/94 and i feel your pain - the 93/94 o2 sensors are different, and only used on these trucks for those years, and thus very expensive for the exact working part, which is denso or denso by way of toyota. Bosch is right out. A couple people have said NGK worked but they don't talk about whether they kept working for a long time. I have 2 years on my genuine Yota replacements with no issues.

since you're not throwing o2 sensor related codes, we can hope it's not the o2 sensors. a bit.

When did you last do the basic tuneup stuff? Plugs, wires, cap, rotor. You want NGK or Denso plugs that you can get anywhere (both are OE, sometimes both on the same engine from the factory). OEM cap & rotor from the dealership are surprisingly cheap considering how much everything else on our trucks costs. I have 2 years on a $50 set of NGK wires with no complaints. OEM wires are Yazaki and cost more than a benjamin.

These ones: http://www.amazon.com/dp/B000CJ8D7Q/?tag=ihco-20

Thanks for the reply.

I don't usually commute in my Cruiser, but I'm taking it 60 miles round trip to work today, and maybe out for lunch to get more drive cycles.

The cap/wires are unknown age but they looked pretty new when I got the truck two years ago, and Slee didn't mention that the cap or rotor should be replaced when they re-sealed the distributor output shaft in the spring. The plugs are two years old.

I thought that bad plugs/wires/cap/rotor would cause higher un-burned HC and CO, but not higher NOx?
 
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You may be right about that.

The drive cycles don't have to be long fwiw. 30 seconds rolling 10 seconds with the key out was what i was doing. In an empty parking lot. Got some funny looks.
 
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i had high NOx readings on my 80 too, replaced the 02's...nothing, replaced vsv to get rid of P0401...nohting, replaced cats...now i am cleaner then a prius!
 
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X2 on the cats....one was a free flow and the other was a part flow...lol
new catco cats made it pass with flying colors
 
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You need the EGR, O2 sensors and catalyst to all be working properly to meet NOx limits. The EGR does most of the work. The reductive side of the 3-way cat does the rest, but it doesn't work so well if there is excess O2 in the gas stream. EGR is easy to check. Both EGR and O2 problems usually throw CEL codes.
 
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You need the EGR, O2 sensors and catalyst to all be working properly to meet NOx limits. The EGR does most of the work. The reductive side of the 3-way cat does the rest, but it doesn't work so well if there is excess O2 in the gas stream. EGR is easy to check. Both EGR and O2 problems usually throw CEL codes.
Thanks, Pinhead! I'm not throwing any codes, I serviced the EGR two years ago ( I'll check it again).

Can anyone point me at the procedure to check the O2 sensors?
 

ToothDr

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My 1993 failed NOx as well here in denver. Replaced my original cats and O2 sensors. Cruiser runs as clean as my 2007 audi. Cats wear out over time and after 20+ years will require replacement. Colorado also tightened the NOx numbers over the last few years.
 
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I fixed egr, O2 and still couldn't get to the NOX 4, got close. Was going to try new cats but left Denver area. I am now back in Ft Collins and will have to buy new cats and O2's and fix EGR to pass. Might need new exhaust as the factory muffler is finally leaking a little.

Will new cats and O2's be enough to pass if EGR is not working?
 
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I fixed egr, O2 and still couldn't get to the NOX 4, got close. Was going to try new cats but left Denver area. I am now back in Ft Collins and will have to buy new cats and O2's and fix EGR to pass. Might need new exhaust as the factory muffler is finally leaking a little.

Will new cats and O2's be enough to pass if EGR is not working?
I'm a little fuzzy, but I think my NOx was pretty high before I repaired my EGR system. It wasn't that hard, just time consuming.

Thanks for all the tips. I think I'm going to try the free re-test after getting it nice and hot and then look into parts.

Any tips on if it helps to have ECT or OD on or off to pass?

I spoke to a shop today that said around $1100 for a new y pipe and two cats. If I choose to do this myself, do the cats have to be welded or do they bolt on? What have you paid for install?
 

Brentbba

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I've said it before here; '94's are notorious for eating O2 sensors. I'd put my money there even if you aren't throwing a rich or lean code. Even following the FSM testing procedure on the sensors won't really tell you if they are good or not.
 
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I've said it before here; '94's are notorious for eating O2 sensors. I'd put my money there even if you aren't throwing a rich or lean code. Even following the FSM testing procedure on the sensors won't really tell you if they are good or not.
Parts Geek has Bosch and Denso. Is there a preference?
 

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