Last year, my Grand Cherokee 4.0L did not pass due to elevated NOx levels so I had the cat. replaced with a CarSound cat, lots of Jeep owners on JU have been using this cat, and passed with flying colors. When I had it tested for this year's inspection, it was 20ppm from being failing the sniffer test. The 4.0L engine does not have an EGR system. What could the problem be? At the time, I had given it a major tuneup, including a high performance ignition coil and had a new air filter and fresh oil. Is the O2 sensor to blame?
NOx almost caused me to fail sniffer test
- Thread starter JeepZJ4.0
- Start date
- Status
Autolite Platinum Plugs
Magnecore 8.5mm Sparkplug wires
Brass tipped rotor and distributer cap
MSD "Blaster" Ignition Coil
Compared to the stuff that came on my Jeep:
Bosch Super Copper PLugs (when tested the 1st time, 3K miles on them)
Mopar Wires (date installed unknown)
stainless steel rotor and cap (date installed unknown)
Magnecore 8.5mm Sparkplug wires
Brass tipped rotor and distributer cap
MSD "Blaster" Ignition Coil
Compared to the stuff that came on my Jeep:
Bosch Super Copper PLugs (when tested the 1st time, 3K miles on them)
Mopar Wires (date installed unknown)
stainless steel rotor and cap (date installed unknown)
Do you have anything like Amsoil Qick Shot, Redline SI-1, Fuel Power, Schafers 131???? I would do as mentioned above and run a can of one of these through your tank. Carboned up pistons or combustion chamber can send NOx levels through the roof a bad o2 sensor can as well. Your o2 sensor should be fine if it is not throwing a code. If you should fail it would be the first thing I would change.
The Jeep has 84,800 miles and I think the 02 sensor hasn't been changed. I am the second owner. It shouldn't last much longer. I'll decarbonize the cylinders on the way back to Houston with some Redline.
- Joined
- Sep 28, 2002
- Messages
- 39,793
If your other specs are in spec ...you don't have 02 sensor issues. The NOX, in the 4.0, is a product of ignition timing. If you've got an OBDI (which I think you should with a Grand and a 4.0 ..maybe not
) .. you may be able to adjust the static timing (retard it). This I have to do with my 3.0 Caravan which also is a Chrysler "no egr" engine Japanese style. Since you said "sensor" you must have an OBDI engine ...now that I think about it. The OBDII's have two.
If timing is not adjustable at the distributor ..see if your crank position sensor has moved. That's the best I can pull out of my arse
If timing is not adjustable at the distributor ..see if your crank position sensor has moved. That's the best I can pull out of my arse
Thank you!!! A symptom of a bad CPS is low idle. I even changed my IAC motor and the idle didn't fix itself so that has to be it! Thank you!quote:
Originally posted by Gary Allan:
See if your crank position sensor has moved. That's the best I can pull out of my arse
Could be carbon buildup in the cylinders.
I deal with that by intermittently (spray for 3 seconds, stop for 5 seconds, etc) spraying about half a can of B12 Chemtool Carb and Choke cleaner into the throttle body with the engine running, revving the engine as necessary to keep it from stalling.
The reason for intermittently spraying it is to keep the cats from getting overheated.
After I did this, my 1996 Ford Contour with 97,000 miles got 2PPM NOx at both 15 and 25MPH. It had never gotten an NOx reading that low before!
After doing this, it might not be a bad idea to change the oil...
EDIT: I wouldn't think the problem would be caused by the O2 sensor, but if it's over 100,000 miles old, you should probably replace it anyway.
I deal with that by intermittently (spray for 3 seconds, stop for 5 seconds, etc) spraying about half a can of B12 Chemtool Carb and Choke cleaner into the throttle body with the engine running, revving the engine as necessary to keep it from stalling.
The reason for intermittently spraying it is to keep the cats from getting overheated.
After I did this, my 1996 Ford Contour with 97,000 miles got 2PPM NOx at both 15 and 25MPH. It had never gotten an NOx reading that low before!
After doing this, it might not be a bad idea to change the oil...
EDIT: I wouldn't think the problem would be caused by the O2 sensor, but if it's over 100,000 miles old, you should probably replace it anyway.
- Status
