gunpilot

It seems my saga involves multiple aspects of different experiences here, so I thought I would post mine to open up for discussion.

Ok, first the basics.

1. Bought the truck with Arizona plates
2. SR5 V6 5SPD 4X4
3. Replaced head gasket
4. Used stock manifolds to make cutom cross pipe that runs under the vehicle instead of in the engine bay

So I get it running after the head gasket and drive it around for about 25 miles to get it ready for the Texas inspection that is required to title it here. It passed the safety part of the inspection, but failed the emissions NOx:

TEST 1

15MPH TEST
(POLLUTANT /STANDARD/ READING /RESULT)
HC 155 122 PASS
CO 1.31% 0.22% PASS
NOX 1046 2411 FAILED

25MPH TEST
(POLLUTANT/ STANDARD /READING/ RESULT)
HC 151 43 PASS
CO 1.68% 0.07% PASS
NOX 956 2152 FAILED

After this test, I jumped on the forum and started my research. Everything pointed to the EGR. I traced all the lines, and actually found that I forgot to reconnect the vacuum hose on the bottom of the vacuum modulator to the EGR! I reconnected it and rushed back to the station for my free retest.

TEST 2

15MPH TEST
POLLUTANT /STANDARD /READING /RESULT
HC 155 95 PASS
CO 1.31% 0.13% PASS
NOX 1046 2793 FAILED

25MPH TEST
POLLUTANT /STANDARD /READING /RESULT
HC 151 57 PASS
CO 1.68% 0.24% PASS
NOX 956 557 PASS

So I passed the 25mph test, but got worse on the 15mph test! BACK TO THE DRAWING BOARD.

After reading more posts on the issue, here are my next steps:

1) Following FSM, test EGR system with vacuum guage
2) Folowwing FSM, test O2 sensor ohms

If both check out okay, I will replace CAT.

I talked to a local mechanic last night, and he did mention that my CAT is original, and blowing a head gasket releases coolant into the exhaust system and kills the CAT!

I also read on here that the VSV is controlled by back pressure in the exhaust. A fellow forum member had similar issues with Downey headers and a free flow cat. With my custom crossover pipe, I am wondering if at 15mph the VSV is not acting right?

I will post follow ups as I get them done.

gunpilot

O2 sensor ohms was 6.2 which is right in the middle of the expected 5-7.

Checked the voltage on the diagnostic terminal and it fluctuated more than 8 times in 10 seconds, so that is good.

O2 sensor eliminated.

rangerruck

I think nox is cat related, but your cat may not be dead yet, it just might have huge chunks in it. I would spend 10 bucks, and do a seafoam treatment first;
well... in your case, i might do one hole can, as the treatment trick, then add another whole can to the gas tank.
Seafoam can break up the crap in your cat, and blow it out, along with the other sludge and water/moisture, that is trapped up in there.

rangerruck

oh yeah, I would wait at least 30 mins between dropping in the last of the fluid/shots, and cranking it back up- 15 mins I don't think will do it for you!

phildelfino

Keep us posted cuz I just failed mine also. Mine was hydrocarbons exceeded, I think. The standard is 220 and I had 222.
A little rich? Replace O2 senser?
Thanks, Phil

gunpilot

Changed out some vaccum lines and blew air to clear out others.

Double checked vacuum connections were correct and all valves worked.

Replaced Cat with a bolt on OEM replacement from O'reilys for $100. Passed emissions!!!!!

sb5walker

High NOX usually comes from failed EGR. Search for help on troubleshooting that. A new cat usually will help bring down NOX, but probably will not make up for a bad EGR - so that must be fixed.