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Need help with passing emissions.

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mike96

15+ Year Contributor
1,010
19
May 6, 2008
Phoenix, Arizona
Long story short (I will elaborate more later) my car won't pass emissions. The car is a 95 talon AWD so the state of AZ can't do the roller test only the exhaust sniff and it keeps failing for high hydrocarbons. I believe it is primarily due to the fact the my car wants to run in the 17:1 - 19:1 afr at idle. As soon as there is a load or I am driving it is right in the high 14:1 - 15:1 where it should be. I have done all the necessary tune up items and have boost leaked it to death and there is none. What else would cause it to only run lean at idle?
 
A bad O2 sensor would cause this. How old is your front O2 sensor by the turbo outlet?
 
New spark plugs and O2 sensors do help considerably for smog. Have you recently done maintenance?
Also you could try one of those things from CNC guaranteed to pass smog.
 
OK. Now that I am out of class and have more time to go over the specifics.

So after moving back down to Phoenix from Las Vegas I have had to (cough, cough) re install certain emissions equipment that had somehow been removed from my car (cough, cough)... The first emissions test I failed required that the charcoal canister needed to be reinstalled and my car was failing for high hydrocarbons at idle. I got the car back together, and everything seemed to be fine. The car ran good and idled fine. I replaced the plug wires and plugs. and fixed multiple vacuum leaks. On the way back to the emissions center it started trying to stall out when I pulled up to stop lights and at idle my WB was registering in the 17 to 19 AFR but only at idle. I got back to the emissions test center and had it re inspected to clear the visual part then went back around to retake the sniff check. Once again it failed for high hydrocarbons. After making it home and letting things cool off for a bit (mostly me) I pulled the intake off the turbo and rechecked for leaks, found none... So there is where I am at. My car runs lean when it idles, and only when it is at idle. Any time there is a load on the engine or the throttle is applied the AFR is right around the 14.7 range where it is suppose to be.

I know that a lean condition will bring the hydrocarbons up, so I am fairly certain my lean idle is causing me to fail emissions. But I need to figure out what is causing my car to run lean at idle.

New spark plugs and O2 sensors do help considerably for smog. Have you recently done maintenance?
Also you could try one of those things from CNC guaranteed to pass smog.
A bad O2 sensor would cause this. How old is your front O2 sensor by the turbo outlet?

o2 sensor is about 2 years old as is the Cat.
 
AF ratio numerically higher than 14.7 is lean not rich, if your vehicle is running correctly. Therefore you shouldn't have excess hydrocarbons (fuel) in the exhaust. The o2 sensor just compares the oxigen content inside and outside the exhaust pipe and that is all. If your engine misfires and the air-fuel mixture doesn't combust properly (or at all) the (unconsumed) oxigen content in the exhaust will show as a lean condition on the af gauge but your exhaust will have excess HCs from unburnt fuel. Proper combustion needs three things - air and fuel at proper ratio and spark. I would check/replace plugs, wires, coils. Check and set your ignition timing. Check your voltage at idle. Check your dwell settings and voltage compensation tablein the ecu and verify that they match your coils. Check the injector spray pattern. If the fuel doesn't come out as a fine mist you may have combustion issues and unburnt fuel post combustion. Try using fuel with ethanol in it. My assumption based on the provided info is that you are misfiring. Good luck.
 
Check your o2 sensor and make sure its working properly.

The nbO2 sensor should be working fine, from what I can tell based on the fact that the the car fluctuates fine around the 14.7 range while under any kind of a load. this tells me that the the ECU is making corrections based nbO2 feedback. I also checked the reading in evoscan and it appears to be cycling fine.

AF ratio numerically higher than 14.7 is lean not rich, if your vehicle is running correctly. Therefore you shouldn't have excess hydrocarbons (fuel) in the exhaust. The o2 sensor just compares the oxigen content inside and outside the exhaust pipe and that is all. If your engine misfires and the air-fuel mixture doesn't combust properly (or at all) the (unconsumed) oxigen content in the exhaust will show as a lean condition on the af gauge but your exhaust will have excess HCs from unburnt fuel. Proper combustion needs three things - air and fuel at proper ratio and spark. I would check/replace plugs, wires, coils. Check and set your ignition timing. Check your voltage at idle. Check your dwell settings and voltage compensation tablein the ecu and verify that they match your coils. Check the injector spray pattern. If the fuel doesn't come out as a fine mist you may have combustion issues and unburnt fuel post combustion. Try using fuel with ethanol in it. My assumption based on the provided info is that you are misfiring. Good luck.

Thank you for the refresher, I am familiar with how the combustion engine works and why I have high HCs, we just recently covered this in class. What I am having problems with is why I am running lean. I cant find any reason for it and need some input as to what to look for.

Plugs and wires have just been done in the last two days, coils were replaced last year when the transistor failed and took a coil with it. I will check the voltage at idle and see what it is at. the alternator is less than 6 months old so the charging system should be fine, the battery on the other hand. I will also take a look at the dwell settings but they have been the same settings for over 4 years with no issues. Not sure how they would have changed but... As for timing I can check it but I have no way of adjusting it, I am not running link and there is no adjustment in ecuflash for base timing. I suppose it may be time to send the injectors out for a cleaning just to make sure they are GTG, if memory is correct it has been about 3 years. I don't typically like doing those myself and would rather spend the $14 per injector to have them done professionally. All fuel here in AZ has about 10% ethanol in it during the hot months. Perhaps I should hit up an E85 station and add a gallon to the tank... until recently the car has been running fine and only reciently started running lean at idle.
 
Run some seafoam through your system, and like Mldsm said, use some ethanol! It burns way hotter and cleaner, so go easy on it while this is in your system.

Never hurts to have a spare exhaust with a decent cat, if the cat's working right and plenty hot, it's hard to fail.

Wonder if turning your boost down a little bit might fix your lean problem.
 
Never hurts to have a spare exhaust with a decent cat, if the cat's working right and plenty hot, it's hard to fail.

Wonder if turning your boost down a little bit might fix your lean problem.

God I hope to have to buy yet another cat. I just replaced it about 2 years ago, maybe less.

How would turning down the boost help with passing emissions when I am failing the idle test???
 
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