95 Dodge dakota, 3.9 V6 two weel drive, Failed NOX, to high

[Richter1234]

I have taken the test several times and it has produced any where from 3.23 to 6.44 NOX in which i need less than 3.00.


The cat is fairly new, The EGR is Brand new, pretty sure i fixed any of the vacuum leaks i have found(By spraying Lubricants on all the hoses.) I have replaced the Distributor cap with the Wires and Plugs. I have cleaned out the EGR system its self(Where the EGR connects to and goes through the exhaust) I have ran The best fuel i can, i have done a full injection cleaning(Running a drip system through the brake booster line) I have used the Guaranteed to pass fuel additive.


The only thing i have not done yet is replace the O2 sensors. I dont have a check engine light on so i figured those dont need to be replaced.
The only problem i can tell the vehicle has is that it runs incredibly cool(At least thats what it looks like on the Temp meter)

Any one have any ideas on what else i can do? I have a friend/mechanic that tells me my Exhaust ports could be plugged up and that i might have to either take them apart and clean them or get a new exhaust system(Manifold and etc...)


Thank you for taking your time reading this and i hope i get some good feedback.

[rhandwor]

Originally Posted by Richter1234

I have taken the test several times and it has produced any where from 3.23 to 6.44 NOX in which i need less than 3.00.


The cat is fairly new, The EGR is Brand new, pretty sure i fixed any of the vacuum leaks i have found(By spraying Lubricants on all the hoses.) I have replaced the Distributor cap with the Wires and Plugs. I have cleaned out the EGR system its self(Where the EGR connects to and goes through the exhaust) I have ran The best fuel i can, i have done a full injection cleaning(Running a drip system through the brake booster line) I have used the Guaranteed to pass fuel additive.


The only thing i have not done yet is replace the O2 sensors. I dont have a check engine light on so i figured those dont need to be replaced.
The only problem i can tell the vehicle has is that it runs incredibly cool(At least thats what it looks like on the Temp meter)

Any one have any ideas on what else i can do? I have a friend/mechanic that tells me my Exhaust ports could be plugged up and that i might have to either take them apart and clean them or get a new exhaust system(Manifold and etc...)


Thank you for taking your time reading this and i hope i get some good feedback.

Feel the top and bottom radiator hose when hot and compare to a vehicle that passes. A thermostat stuck open will cause a vehicle to fail emissions.
Spray along the intake manifold and check for leaks. My 1994 had a carburetor this is a major problem in failing emissions. Lean out the mixture slightly.

[Richter1234]

I will check that out, Though wouldnt a Thermo stat stuck open cause the vehicle to run hot since the Coolant wont have a chance to cool off while in the radiator? Also, What about the fuel filter/pump? The whole system is inside the tank so i dont have easy acces to it(and i dont think its been changed in a very long time, Though it doesnt feel like i have a clogged filter and what not). I will have to either get a jack stand or a second person to help me with that. Tonight when i get home frome school i will check for a manifold leak, Should i just spray around where it connects or all the Bolts as well as where it connects?

Also what type of spray should i use? Carb cleaner(or something similar) or an actual lubricant?


Also on the Topic of the vehicle running cool. After about 20 minutes of the vehicle sitting i took off the cap and stuck in a thermometer and it read just around 200(Even though the temp gauge showed just above the C. If the meter went straight this is where it would show
[C (here).................. H] and this is after a good 40 mile drive, Which is what i did before i went to take my emissions test.



Thanks for the input, Ill try these things and get back to you either tonight or tomorrow.

[rhandwor]

You can use wd40 or carburetor cleaner. Look for leaks edge of intake or carburetor or injector throttle body base and hoses for leaks.

[Richter1234]

All right i will try that out, I found one a few days ago, It was a little rubber vacuum plug that was cracked. I will check for more things.

[theFREAKnasty82]

NOX is caused by high cylinder head temps. Your gauge may be reading cool, but it's not uncommon for the gauges to not work. Also, if you have replaced your spark plugs recently, make sure that they're the correct heat range. Try to also get an upper cylinder head cleaner; that will remove a good amount of carbon that is built up on the upper cylinder head, without having to remove the heads.