Help! fj80 cant pass emissions

[Ali FJ80]

Hi, hope you guys can help solve this problem. I have a 91 fj80 with with the 4.0 3f motor with a lift and 33's, aside from that its stock with 112k on the clock and runs great. I went for emissions and the CO reading was at 70 or so with the limit being 25. I had the oil changed, at which time they ran some sort of engine cleaner through it and put in a new K&N drop in air filter. The truck now registered at a 65 which is still over double the limit. No check engine light on or anything. Any suggestions would be greatly appreciated. Also not sure if it matters but I dont drive it much, maybe 3000 miles in the last year or so.
Thanks,
Ali

 

[nakman]

Ok, I'll bite.. how new are the O2 sensors? If they're real old, they could be the culprit, as they're sending bad data to the ECU so your mix is too rich. It's very possible that can happen but not be bad enough to throw a code. But wait.. how are the cats? If they're old, then not everything is getting burned, so then that's why your O2 sensors went bad.

It's all relative, when I had a 3FE that's what I had to do to get it to pass... hth.

 

[Uncle Ben]

Hi, hope you guys can help solve this problem. I have a 91 fj80 with with the 4.0 3f motor with a lift and 33's, aside from that its stock with 112k on the clock and runs great. I went for emissions and the CO reading was at 70 or so with the limit being 25. I had the oil changed, at which time they ran some sort of engine cleaner through it and put in a new K&N drop in air filter. The truck now registered at a 65 which is still over double the limit. No check engine light on or anything. Any suggestions would be greatly appreciated. Also not sure if it matters but I dont drive it much, maybe 3000 miles in the last year or so.
Thanks,
Ali

It almost sounds like the truck is stuck in Open mode. Have you ever replaced the o2 sensor? If not thats where I would begin!

 

[Uncle Ben]

Ok, I'll bite.. how new are the O2 sensors? If they're real old, they could be the culprit, as they're sending bad data to the ECU so your mix is too rich. It's very possible that can happen but not be bad enough to throw a code. But wait.. how are the cats? If they're old, then not everything is getting burned, so then that's why your O2 sensors went bad.

It's all relative, when I had a 3FE that's what I had to do to get it to pass... hth.

Sorry Nak....should have read down the post first.....

Ya....what he said!

 

[corsair23]

Had a similar problem with my 1982 pickup long time ago...Obviously take the suggestions above for sure but also get out and drive that thing for awhile...Put some good hiway miles on it to really clean it out...Romp on the gas etc. I went out and drove about 50 miles, went back and it passed. Of course that back before the new testing centers came about...

Good luck!

 

[Ali FJ80]

Thanks guys, I found the records which show both o2 sensors were changed last july and after that it passed with a CO reading of about 4.8. I called the mechanic who did the work and he said to run injector cleaner since it hasn't been used much and have the cat checked as it is the original. Will try these and take it for a long run with the cleaner.

Thanks,
Ali

 

[Hulk]

Here's what you want:
BG 44K® Power Enhancer™

I always get the stuff in the can.