Failed smog

[94xjstud]

I went to get my jeep smog and it failed. The guy say that it failed becuase the engine appeared to be being over worked. He was not sure of the problem but said it could be a clogged cat, bad O2 sensor, intake leak or something else. Not sure what that means but here is what I have.

94 xj, straight six, intake routed through the cowl, magna flow 40 series exhaust (about 3 years old), 5" lift, D30 - 4.56 gears and aussie locker, D44 4.56 gears and aussie locker and 33" tires.

Before the smog, I recently did an oil change, transmission fluid flush, new oil pressure switch and changed the valve cover gasket. Since I did the value cover gasket and oil change, my oil pressure gauge was been consistantly at about 60.

Any ideas? I want to do as much as possible on my own because I am on the unemployment budget

 

[Saudade]

He should have given you a printout of the smog test. It will tell you *exactly* what failed. Post the numbers.

 

[94xjstud]

It looks like I failed this:
NO (PPM)
15 mph - MAX(517) AVE(203) MEASURED(852)
25 mph - MAX(539) AVE(233) MEASURED(674)

 

[joe_peters]

"Nitrous oxide is produced at very high temperatures, so anything that lowers the operating temperature of an internal combustion engine would reduce N2O emissions."

Your engine combustion chamber temperatures are too high. Could be the result of running too lean.

Instead of us GUESSING, how about you post up ALL the results of your smog test so we can get the full picture?

 

[1990JEEPXJ]

have you ever done a sea foam treatment? through the intake and some in the tank?

 

[94xjstud]

%CO2 %O2 HC (PPM) CO (%) NO (PPM)
Test RPM MEAS MEAS MAX AVE MEAS MAX AVE MEAS MAX AVE MEAS
15
1724
15.1
0.0
63
26
22
066
0.04
0.03
517
203
852
Fail
25
1776
15.2
0.0
38
16
18
0.08
0.05
0.03
539
233
674
Fail


Sorry it got a little messed up but here are the full smog results. Also did a Lambda Calculator thing and got:
15 mph - Lambda=1 with a Air/fuel ratio of 14.7
25 mph - Lambda=.9999 with a Air/fuel ratio of 14.7


No I have never used sea foam

 

[94xjstud]

Crap, it looked like a table when I put it in here and not just like a list of numbers sorry. I'll try to fix it

 

[94xjstud]

15 mph:
RPM - 1724
%CO2 - 15.1
%O2 - 0.0

HC (PPM):
MAX - 63
AVE - 26
MEAS - 22

CO(%):
MAX - 0.66
AVE - 0.04
MEAS - .03

NO (PPM)
MAX - 517
AVE - 203
MEAS - 852
_________________


25 mph:
RPM - 1776
%CO2 - 15.2
%O2 - 0.0

HC (PPM):
MAX - 38
AVE - 16
MEAS - 18

CO(%):
MAX - 0.80
AVE - 0.05
MEAS - .03

NO (PPM)
MAX - 539
AVE - 233
MEAS - 674
________________

I think that this should be easier to read

 

[joe_peters]

Yeah, much better.

Your HC--hydro carbons--is on the bottom end of the scale. If those were raised it would cool the combustion chamber temperatures and reduce the NO.

When was the last time the o2 sensor was changed?

 

[94xjstud]

Probably not since I have had it (5 Years).

 

[joe_peters]

Depending on the type they are good for 60-80k miles, but can fail earlier.

I would pick up a Bosch o2 sensor and see what that gets you.

 

[94xjstud]

I was looking around for leaks and spotted a good sized (1-3") crack in my exhaust manifold where the two pipes connect. IIRC that is very common on stock 4.0L manifolds.

I would like to fix this asap and cheap, would JB Weld work or do I need to take it completely off to get it welded.

 

[nick86]

I was looking around for leaks and spotted a good sized (1-3") crack in my exhaust manifold where the two pipes connect. IIRC that is very common on stock 4.0L manifolds.

I would like to fix this asap and cheap, would JB Weld work or do I need to take it completely off to get it welded.

Just buy an aftermarket one, Dorman makes a kinda fairly cheap one w/ flex at each end I believe.