Need help passing smog
#1
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Year: 1994
Model: Cherokee
Engine: 4.0 HO motor
Need help passing smog
got a 94 Cherokee sport all stock put new 02 sensor on but emissions are still high, mechanic said had high nox.. Not sure what this means? any advice helps.. Thanks guys
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Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Nitrogen Oxide "forms" at combustion temps that are high. 2,800, 3,000 * maybe. One purpose of the EGR valve,(Exhaust Gas Resurilation), is to reduce combustion temps and the formulation of N0x. Likely a good place to look. Right off hand, that is all I have..now.
The valve is low on the exhaust manifold, (middle) controlled with vacuum, controlled with a solenoid. I think. 94 is similar to mine I believe. My EGR solenoid is on my drivers inner fender, should apply vacuum to it when the puter' says. That opens it to let exhaust into the intake manifold. I can't say for sure mine's working or not.
The valve is low on the exhaust manifold, (middle) controlled with vacuum, controlled with a solenoid. I think. 94 is similar to mine I believe. My EGR solenoid is on my drivers inner fender, should apply vacuum to it when the puter' says. That opens it to let exhaust into the intake manifold. I can't say for sure mine's working or not.
Last edited by DFlintstone; 11-01-2012 at 10:58 PM.
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Year: 1992 Cherokee Sport
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NEVER run ANY additive during an emissions test, that usually screws up the results big time. Do the test about a week after you get the additive out.
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#13
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Year: 1994
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Engine: 4.0 HO motor
Cat tested good and just put new o2 right before
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Year: 90,84
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Engine: 4.0,2.5
Just fielding a question. Is it different getting an estament to pass smog, than say to have the belt changed? If you are not somehow "stuck".... I mean, we all have seen what they do. Sometimes another shop can help.
High Nox (too high compression) on a 94? Do you hear pinging?
High Nox (too high compression) on a 94? Do you hear pinging?
#15
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Year: 1995
Model: Cherokee
Engine: 4.0
High Nox means it's running lean, had the same problem last sept. I also changed the o2 sensor that made it go up, check your CCV it's easy to replace and cheap. Look at your exhaust manifold it most likely has a crack where the pipes connect, that sloved my high readings. You could also go with a cooler plug I belive the plug is champion RC9YC with the same gap that should help but it won't fix the problem. If you can pull a plug and post a picture also the reading you got from the smog test would help.