still failing texas emissions

[tac0meat]

ok ive had the thing tested like 5 times and cant seem to pass, i have things done to it each time. the only part that i keep failing is the NOX. i fail it on both the low speed (15mph) and high speed (25mph) tests. heres a breakdown of what its been doin:

---------------limit------15mph---------------limit------25mph
test one: (lost sheet but the NOX were: )
NOX(ppm)------1046-------2050-----------------956-----1950

test two(replaced second cat and pvc valve <50miles on new cat):
HC(ppm)-----151--------9 ----------------------155------14
CO(%)--------1.68-------0.00-------------------1.31------0.00
NOX-----------1046--------1680------------------956-----1470
dilution------->6.0--------14.4------------------->6.0 -----14.4

test 3(>500 miles on new cat)
HC(ppm)----151----------11----------------------155-------13
CO(%)-------1.68---------0.00 -------------------1.31------0.00
NOX-----------1046---------1374-------------------956-----1704
dilution----->6.0-----------14.4------------------->6.0-----14.3

test 4(guy claims he adjusted timing by removing a plug in a wiring harness under hood)
HC(ppm)-----151--------12----------------------155------17
CO(%)--------1.68-------0.00-------------------1.31------0.00
NOX-----------1046--------1516------------------956-----1488
dilution------->6.0--------14.3------------------->6.0 -----14.3

test 5(at different shop who claims all they did was use a fan to cool it down and let it sit for an hour)
HC(ppm)-----151--------39----------------------155------98
CO(%)--------1.68-------0.04-------------------1.31------0.16
NOX-----------1046--------891------------------956-----972
dilution------->6.0--------14.6------------------->6.0 -----14.8

test 6(back at my usual emissions shop, letting engine cool down for an hour with fan)
HC(ppm)-----151--------18----------------------155------24
CO(%)--------1.68-------0.00-------------------1.31------0.01
NOX-----------1046--------1551------------------956-----1503
dilution------->6.0--------14.5------------------->6.0 -----14.5

i watched all test performed except test number 5, which was at an "emissions specialist". the place that replaced my cat (not the same place i had my testing done at) said that my front cat is still good, and only need to replace the rear cat. after test 4, i replaced the plug that was supposed to advance my timing. tommorrow im gonna try running it ice cold just to see what happens (guy with 91 aerostar with same engine/tranny as me did it this way and supposedly passed). sorry for the long post, but im hopin somebody will understand what goin on with these numbers and have a suggestion to get it to pass. thanx guys!

 

[Soundguy01tx]

Frankly man, that is why I got a new ride. And Igot my inspection done PRE Emissions testing haha. We went ahead and go the 91 tested the week before testing went into effect. Sucks that you keep failing man.
--Bryan

 

[RiverRat]

Looks like you engine is running great. Seriously, those are good numbers for an older engine. Your high NOX should be cause by an EGR issue.

 

[tac0meat]

thats what the guys at the emissions place said, they said it was either the cat or egr, but i have a 91, which doesnt have an egr. im thinkin it might be the second cat

 

[Chew_12]

HOw many miles are on your truck?

 

[tac0meat]

about 338,500

 

[dogfriend]

My book on Ford FI and Engine Control says that a lean mixture will raise the combustion temp and increase the NOx.

Running cold will tend to reduce NOx as does running rich (but will increase CO and HC).

You may pass running cold, but if you want to fix it, look for causes of running lean (air leaks, bad O2 sensor, clogged fuel injectors, bad fuel pressure)

Notice in Test #5 your HC and CO went up slightly and NOx went way down, this was on the right track

 

[DonM]

91 dont have an EGR vavle, correct?

Just trying to narrow it down for ya.

 

[tac0meat]

ok i retested today with the engine cold. i had let it sit for about 7 hours with the hood up to make sure it was planty cool. then we put straight on the dyno with no warmup. heres the results:
---------------limit------15mph---------------limit------25mph
HC(ppm)-----151--------18----------------------155------20
CO(%)--------1.68-------0.00-------------------1.31------0.00
NOX-----------1046--------1237------------------956-----1243
dilution------->6.0--------14.4------------------->6.0 -----14.4

the guy said that if there is carbon buildup than that can make the nox go up. he suggested runnin a a treatment through it. so right now im workin on goni through a tank of chevron gas with the techron concentrate added which is supposed to get rid of or lessen carbon deposits. once ive gone through this tank gonna let the engine get cold and run the test again.

BTW- on test number 5, im pretty confident (along with the emmisions guys) that the place that ran this test, simply put the sniffer up a different cars tailpipe. the guy told me that he used the big fan to cool it down for about an hour, ran the test, and it passed, he said he could give me the sticker, but it would cost 39.50 and that i have a free reinspection at the other emmissions place. figure he says that, i fail at the orignal place (again) come back to him, and he passes me all while makin 39.50 plus the 20 bux he charged me to supposedly figure out what was wrong and why i wasnt passing

 

[dogfriend]

Originally posted by tac0meat


BTW- on test number 5, im pretty confident (along with the emmisions guys) that the place that ran this test, simply put the sniffer up a different cars tailpipe.

You are probably right because it doesnt fit with the rest of the results.

A guy that I once worked with knew of a shop in Oakland that could make any car pass. They used the sniffer in another cars tailpipe technique.

If it is carbon buildup, you might want to try Seafoam or the equivalent Ford cleaner.


Dead Link Removed
Dead Link Removed

 

[tac0meat]

that seafoam stuff looks interesting, im gonna see how my truck does tommorrow, if its still no passing then im gonna try the seafoam.

donm-your right, i dont have an egr. from what ive read, im startin to wish i did, the egr lowers the nox emssions greatly

 

[tac0meat]

WOOHOO!!! PASSED!!!!

i guess the techron stuff did the trick. ran it today, and it didnt pass on the 15mph test, but it was close enough for the testing computer to go into "second chance" mode which retests it again, and it passed. we then ran the test as my official reinspection, and it passed. the ratings kept gettin lower a guess as the techron did its work. heres the results:

test 8: (practice run)
---------------limit------15mph---------------limit------25mph
HC(ppm)-----151--------15----------------------155------19
CO(%)--------1.68-------0.00-------------------1.31------0.00
NOX-----------990--------966--------------------905------724
dilution------->6.0--------14.4------------------->6.0 -----14.3

test 9: (official reinspection)
---------------limit------15mph---------------limit------25mph
HC(ppm)-----151--------19----------------------155------10
CO(%)--------1.68-------0.01-------------------1.31------0.00
NOX-----------990--------946-------------------905-------673
dilution------->6.0--------14.3------------------->6.0 -----14.3