Cali smog help - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Lehr98 · 03-07-2019, 04:01 AM

I’m trying to make my s13 coupe pass smog. Here are my results. https://imgur.com/gallery/PISIBhy I am planning on using seafoam, replacing cat and charcoal cannister, try to clean the egr and bpt. Is there anything else you guys recommend?

jedi03 · 03-07-2019, 07:31 AM

fresh fuel, run it for at least 15 min before testing, fresh oil change, new spark plugs/wires, that's all i can think of for now...

240sxTuck · 03-07-2019, 08:01 PM

Not as bad as mine, lol. Gross Polluter all across the board! I just got mine done hot, which is pricey, but easy to do. I plan on passing legit next time i need to smog it.

Cat should be the last thing you replace. I would start small. Go ahead and seafoam it (probably gonna wanna change your spark plugs afterwards). Check for vacuum leaks. Make sure all your solenoids are hooked up right, and working (EGR, SCV, AIV). Make sure it's timed and idling correctly (20 degrees BTDC, 700 +/- 50 RPM). Make sure there are no exhaust leaks. Check for EGR, BPT, AIV, and SCV function. If all that checks out, replace the cannister.

I'm no expert at all, but your results makes me think there's something wrong with your valves or timing (assuming everything else i mentioned is working). Check valve lash, and make sure they're all seating properly. I would also do a compression test on all 4 cylinders. It can tell you if you have a bent valve, or if they're opening early. It might also be a good idea to check your injectors, make sure they're not staying on too long. It's bizarre to me that your HC and CO are fine on the low speed test, but GP on the high speed test, and your NOx is the opposite. What was your CO2% for each test? High amounts of HC and CO means there's not enough heat to burn off all the fuel in the cylinder, and won't produce a lot of CO2. High NOx can mean there's too much heat in the cylinder.

It would also help to know how well the engine runs. is it smooth or rough? are their any RPM ranges where it starts performing poorly?

banandana · 03-08-2019, 12:43 PM

Quote:

Originally Posted by 240sxTuck

Not as bad as mine, lol. Gross Polluter all across the board! I just got mine done hot, which is pricey, but easy to do. I plan on passing legit next time i need to smog it.

Cat should be the last thing you replace. I would start small. Go ahead and seafoam it (probably gonna wanna change your spark plugs afterwards). Check for vacuum leaks. Make sure all your solenoids are hooked up right, and working (EGR, SCV, AIV). Make sure it's timed and idling correctly (20 degrees BTDC, 700 +/- 50 RPM). Make sure there are no exhaust leaks. Check for EGR, BPT, AIV, and SCV function. If all that checks out, replace the cannister.

I'm no expert at all, but your results makes me think there's something wrong with your valves or timing (assuming everything else i mentioned is working). Check valve lash, and make sure they're all seating properly. I would also do a compression test on all 4 cylinders. It can tell you if you have a bent valve, or if they're opening early. It might also be a good idea to check your injectors, make sure they're not staying on too long. It's bizarre to me that your HC and CO are fine on the low speed test, but GP on the high speed test, and your NOx is the opposite. What was your CO2% for each test? High amounts of HC and CO means there's not enough heat to burn off all the fuel in the cylinder, and won't produce a lot of CO2. High NOx can mean there's too much heat in the cylinder.

It would also help to know how well the engine runs. is it smooth or rough? are their any RPM ranges where it starts performing poorly?

PS california allows +/- 3 degrees of ignition timing from factory spec or you will fail smog.

I've heard adjusting the idle to just below 1000rpm will help in some cases with emissions when testing. Something around 1100 is the limit afaik

Check the ECU diagnostics mode to see if the o2 sensor is reading rich or lean; it'll tell you if the ECU is trying to trim fuel up or down. Replace the o2 sensor if it's old. Check for unmetered air.

240sxTuck · 03-09-2019, 11:57 PM

Quote:

Originally Posted by banandana

PS california allows +/- 3 degrees of ignition timing from factory spec or you will fail smog.

I've heard adjusting the idle to just below 1000rpm will help in some cases with emissions when testing. Something around 1100 is the limit afaik

Check the ECU diagnostics mode to see if the o2 sensor is reading rich or lean; it'll tell you if the ECU is trying to trim fuel up or down. Replace the o2 sensor if it's old. Check for unmetered air.

TBH, the O2 sensor won't tell you much unless you're looking at a oscilloscope. Gotta see it in the graph to really get a decent understanding of what's going on, otherwise it's just a bunch of meaningless flashes on the dash

banandana · 03-10-2019, 04:35 PM

Quote:

Originally Posted by 240sxTuck

TBH, the O2 sensor won't tell you much unless you're looking at a oscilloscope. Gotta see it in the graph to really get a decent understanding of what's going on, otherwise it's just a bunch of meaningless flashes on the dash

The information in the full service manual will show you how to put the car into a diagnostics mode which flashes 2 LEDs on the ECU depending on it running 5%+ rich or lean, or within spec. Just using the dash light won't get you anywhere

03-07-2019, 04:01 AM	#1
Lehr98 Join Date: Apr 2018 Location: CA Age: 23 Posts: 17 Trader Rating: (0) Feedback Score: 0 reviews	Cali smog help I’m trying to make my s13 coupe pass smog. Here are my results. https://imgur.com/gallery/PISIBhy I am planning on using seafoam, replacing cat and charcoal cannister, try to clean the egr and bpt. Is there anything else you guys recommend?

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03-07-2019, 07:31 AM	#2
jedi03 Nissanaholic! Join Date: Jul 2008 Location: albuquerque Posts: 1,784 Trader Rating: (8) Feedback Score: 8 reviews	fresh fuel, run it for at least 15 min before testing, fresh oil change, new spark plugs/wires, that's all i can think of for now...

03-07-2019, 08:01 PM	#3
240sxTuck Join Date: Sep 2016 Location: Sonoma County, CA Age: 26 Posts: 18 Trader Rating: (0) Feedback Score: 0 reviews	Not as bad as mine, lol. Gross Polluter all across the board! I just got mine done hot, which is pricey, but easy to do. I plan on passing legit next time i need to smog it. Cat should be the last thing you replace. I would start small. Go ahead and seafoam it (probably gonna wanna change your spark plugs afterwards). Check for vacuum leaks. Make sure all your solenoids are hooked up right, and working (EGR, SCV, AIV). Make sure it's timed and idling correctly (20 degrees BTDC, 700 +/- 50 RPM). Make sure there are no exhaust leaks. Check for EGR, BPT, AIV, and SCV function. If all that checks out, replace the cannister. I'm no expert at all, but your results makes me think there's something wrong with your valves or timing (assuming everything else i mentioned is working). Check valve lash, and make sure they're all seating properly. I would also do a compression test on all 4 cylinders. It can tell you if you have a bent valve, or if they're opening early. It might also be a good idea to check your injectors, make sure they're not staying on too long. It's bizarre to me that your HC and CO are fine on the low speed test, but GP on the high speed test, and your NOx is the opposite. What was your CO2% for each test? High amounts of HC and CO means there's not enough heat to burn off all the fuel in the cylinder, and won't produce a lot of CO2. High NOx can mean there's too much heat in the cylinder. It would also help to know how well the engine runs. is it smooth or rough? are their any RPM ranges where it starts performing poorly?