decipher CA smog fail
#1
Junior Member
Thread Starter
decipher CA smog fail
1999 sport 4.0 just broke 280,000.
Oil change 2 months ago, with air filter.
Plugs with cap,rotor and wires 3 months.
After reading thru several threads on subject have come to assumption that my girl is running to lean and is why failed NOx test, also that O2 reading above 1%. My concern is what the other 2 gas readings might show.
Done after first test :
Found and added fan shroud, jy find .
Checked for exhaust leaks, incomplete weld right before cat on top- plugged.
Checked intake-exhaust bolts, re-tighten in pattern found some of the rear bolts on the loose side.
Can of sea foam in 3/4 tank and ran down to just about walking empty.
Vacuum lines seem good, still checking every time hood opened.
Cat is 2 years old, out of state so had to get carb compliant one. Updated exhaust manifold, old one was cracked ( the one with expansion points).
Newish radiator and coolant
No codes thrown or stored, check by me and the smog shop before each test.
She runs good all the way around, very small hiccups at idle, smooth no hesitations.
Test 1
Test 2
Oil change 2 months ago, with air filter.
Plugs with cap,rotor and wires 3 months.
After reading thru several threads on subject have come to assumption that my girl is running to lean and is why failed NOx test, also that O2 reading above 1%. My concern is what the other 2 gas readings might show.
Done after first test :
Found and added fan shroud, jy find .
Checked for exhaust leaks, incomplete weld right before cat on top- plugged.
Checked intake-exhaust bolts, re-tighten in pattern found some of the rear bolts on the loose side.
Can of sea foam in 3/4 tank and ran down to just about walking empty.
Vacuum lines seem good, still checking every time hood opened.
Cat is 2 years old, out of state so had to get carb compliant one. Updated exhaust manifold, old one was cracked ( the one with expansion points).
Newish radiator and coolant
No codes thrown or stored, check by me and the smog shop before each test.
She runs good all the way around, very small hiccups at idle, smooth no hesitations.
Test 1
Test 2
Last edited by GronHog; 02-29-2016 at 12:05 AM.
#3
Junior Member
Thread Starter
Stayed a 210 before shroud upgrade, now under 210. Just bought a new temp sensor, cause sometimes it stays low then jumps up to 210. Also picked up a 280 stat. Ohm tested injectors, all tested between 12.8-13. Just finished putting 32oz of water thru engine seeing if can decarbon chambers. Radiator and coolant (yellow) 7 months new.
Last edited by GronHog; 02-28-2016 at 04:52 PM. Reason: forgot radiator
#4
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Join Date: Feb 2010
Location: Oroville, CA
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Year: 1995
Model: Grand Cherokee
Engine: 4.0 with all of the noise and clatter
High combustion chamber temperature is what causes high NOX emissions. Decarbonizing the combustion chambers might help some.
#6
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#10
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Never has back fired, good acceleration cold or warmed up. Just slight fluctuations at idle. I assume she is running lean due to the amount of O2 measured. Just trying to figure out which direction to start throwing money at. Seeing if the HC and CO counts give a direction to start in
#11
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Join Date: Mar 2010
Location: Georgia
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Year: 99 94
Model: Cherokee (XJ)
Engine: I6
Originally Posted by GronHog
Never has back fired, good acceleration cold or warmed up. Just slight fluctuations at idle. I assume she is running lean due to the amount of O2 measured. Just trying to figure out which direction to start throwing money at. Seeing if the HC and CO counts give a direction to start in
Has the O2 sensor ever been replaced?
Mine was not throwing a check engine light and it was bad.
#12
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Join Date: Aug 2009
Location: Murrieta, CA
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Year: 1993
Model: Cherokee
Engine: 4L
Spend the $60 at a pass or don't pay test and repair facility. They always seem to find a way to make it pass when there's no money in it for them to make you pay twice.
#14
Junior Member
Thread Starter
I think she has a exhaust leak at intake /exhaust gasket, back half of bolts were not torqued down, a bit loose. Project for this weekend
Last edited by GronHog; 03-01-2016 at 12:31 PM.