84 CFI won’t pass CA smog
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Joined: Oct 2021
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From: Long Beach CA
84 CFI won’t pass CA smog
Hi all,
I’ve been trying to get my 84 smogged the last couple of weeks but it fails every time. The issue is it has insanely high NOx readings at both 15 and 25 mph. I’ve heard that the biggest reason cars will have high NOx is because of a faulty EGR system. I replaced the valve and confirmed operation of the solenoid. The O2 sensor is relatively new. The cat is new. No mods other than aftermarket mufflers. I don’t know how else to lower the NOx. Thanks in advance.
I’ve been trying to get my 84 smogged the last couple of weeks but it fails every time. The issue is it has insanely high NOx readings at both 15 and 25 mph. I’ve heard that the biggest reason cars will have high NOx is because of a faulty EGR system. I replaced the valve and confirmed operation of the solenoid. The O2 sensor is relatively new. The cat is new. No mods other than aftermarket mufflers. I don’t know how else to lower the NOx. Thanks in advance.
Drifting
Joined: Feb 2016
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From: Simi Valley CA
I read an online hack that if you add about 12 oz. of 91% isopropyl alcohol to your tank of gas it will reduce the Nox. The engine temp plays a big role in it too. I have a 93 Jeep Cherokee. I replaced the engine fan with a cheap electric fan. In summer it was not able to keep the coolant temp below the half way mark that it usually runs in. Just above half was enough to make it fail on Nox, but still stay cool enough to not overheat. I put the mechanical fan back on and it passed. Plus the fact that my registration was due in July where I used to have it smogged at the hottest time of the year.
Safety Car
Joined: Nov 2005
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From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
Like mentioned...Your engine must be running hot while testing and you have high combustion chamber temperatures which is giving you the high Nox reading. Things to check, radiator, clear radiator path (this can be an issue with debris buildup up front and blocking air flow) and thermostat is working properly. What is your engine temp while on the roller?
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Joined: Oct 2021
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From: Long Beach CA
Like mentioned...Your engine must be running hot while testing and you have high combustion chamber temperatures which is giving you the high Nox reading. Things to check, radiator, clear radiator path (this can be an issue with debris buildup up front and blocking air flow) and thermostat is working properly. What is your engine temp while on the roller?
Drifting
Joined: Mar 2006
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From: Wabasha Mn
Like mentioned...Your engine must be running hot while testing and you have high combustion chamber temperatures which is giving you the high Nox reading. Things to check, radiator, clear radiator path (this can be an issue with debris buildup up front and blocking air flow) and thermostat is working properly. What is your engine temp while on the roller?
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From: Long Beach CA
Your cooling fan kicks on at 228 I think so you might put in a 180 t stat or you could ground the temp sender wire on passenger side cylinder head between #6 an #8 so the fan will run all the time when you turn the ignition on. Also a friend emptied his radiator and refilled with straight water and his nox dropped and he passed inspection. Worth a try.
Intermediate
Joined: Apr 2010
Posts: 30
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From: Yorba Linda CA
Hi all,
I’ve been trying to get my 84 smogged the last couple of weeks but it fails every time. The issue is it has insanely high NOx readings at both 15 and 25 mph. I’ve heard that the biggest reason cars will have high NOx is because of a faulty EGR system. I replaced the valve and confirmed operation of the solenoid. The O2 sensor is relatively new. The cat is new. No mods other than aftermarket mufflers. I don’t know how else to lower the NOx. Thanks in advance.
I’ve been trying to get my 84 smogged the last couple of weeks but it fails every time. The issue is it has insanely high NOx readings at both 15 and 25 mph. I’ve heard that the biggest reason cars will have high NOx is because of a faulty EGR system. I replaced the valve and confirmed operation of the solenoid. The O2 sensor is relatively new. The cat is new. No mods other than aftermarket mufflers. I don’t know how else to lower the NOx. Thanks in advance.
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Joined: Oct 2021
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From: Long Beach CA
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From: Long Beach CA
Safety Car
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From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
IMO if your cooling system is completely ok and your EGR system is OK, it may be your fuel system. What is your fuel pressure set to? It may be too lean. Set it to 13psi and you should be fine. BTW, installing a 180* will do NOTHING to get your temps down. You could put a 160* and if your system is NOT up to par, once the stat is full open, it's full open and it will still get hot or over heat. Not saying your system is getting too hot since you said 200* which is fine if it stays there. Something is causing the high temp in the cylinders. I would check your FP for sure.
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From: Long Beach CA
IMO if your cooling system is completely ok and your EGR system is OK, it may be your fuel system. What is your fuel pressure set to? It may be too lean. Set it to 13psi and you should be fine. BTW, installing a 180* will do NOTHING to get your temps down. You could put a 160* and if your system is NOT up to par, once the stat is full open, it's full open and it will still get hot or over heat. Not saying your system is getting too hot since you said 200* which is fine if it stays there. Something is causing the high temp in the cylinders. I would check your FP for sure.
Le Mans Master
Joined: Aug 2017
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From: New Jersey
Do you have the ability to log the O2 sensor at speed? Have you replaced the O2 sensor? And if so, what type did you use... NOx is generally caused by heat as said above... I'd suspect you're going lean on the rollers.
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From: Long Beach CA
I don’t have any way of reading sensor data. I’m going to replace the O2 sensor with a Delco one instead of the Bosch one it has.
Melting Slicks
Joined: Dec 2009
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You can jump the ALDL connector like your reading codes. Fire it up, the CEL will flash fast or slow. Fast when hot, should slow down when you rev it. This is showing O2 activity.
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From: Long Beach CA
I never knew this and it says nowhere in my FSM that I’m able to read what the O2 sensor is doing without a scanner. Thanks for the info. Is there a way to tell what the A/F ratio is just from the CEL flashes?
Le Mans Master
Joined: Aug 2017
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From: New Jersey
in the FSM it is called field test (service) mode? I recall reading about it. Not if it was in the manual though. Maybe in the emissions/diagnostic section may have more info.
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From: Long Beach CA
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Merely asking out of curiosity. What brand gasoline are you running? Shell keeps advetising that their gas has nitrogen based cleaners in their gasoline. I suspect the amount is small, but no point in adding to the amount of nitrogen that gets run through a hot combustion process if one is getting high NOx readings in an emission test.
You indicated that your EGR appears to be working. That's good, as that reduces the peak combustion temperatures. As a previous poster mentioned, and I agree, that adding a higher percentage of ethanol should reduce the peak combustion temperature down a bit, reducing NOx.
I'm on the fence about recommending retarding the timing a couple degrees. Although the EGT will be slightly higher, the peak combustion temperature should drop a touch in the process though. So, I don't know what to advise on that front.
You indicated that your EGR appears to be working. That's good, as that reduces the peak combustion temperatures. As a previous poster mentioned, and I agree, that adding a higher percentage of ethanol should reduce the peak combustion temperature down a bit, reducing NOx.
I'm on the fence about recommending retarding the timing a couple degrees. Although the EGT will be slightly higher, the peak combustion temperature should drop a touch in the process though. So, I don't know what to advise on that front.
Drifting
Joined: Feb 2016
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From: Simi Valley CA
Merely asking out of curiosity. What brand gasoline are you running? Shell keeps advetising that their gas has nitrogen based cleaners in their gasoline. I suspect the amount is small, but no point in adding to the amount of nitrogen that gets run through a hot combustion process if one is getting high NOx readings in an emission test.