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Discussion Starter #1 (Edited)
HIGH N0X is the issue. which everyone tells me is either LEAN/ or bad cat. I am pissed off to no ends! how does a car fail smog 3 times??? wtf
Lets say MAX N0X range is from is 730-800 and I've been @ 1700-3200 range. everything passes except for the damn n0x being super high. i have tried @14timing and also 17.5 degrees timing, "tune-up" and a few other tricks. I HAVE NOT verified with a wideband that it is running lean and yes have tried 3 different cats and 2 simultaneously. and also changed 02 sensor out with a new one. i have played with the "SMOG LAMBDA CALCULATOR" if you guys need a pic of the results let me know if it will help....


so here's some background information i got the shell from a acquaintance/guy i previously bough parts off, he got the swap in a parts trade and the "CAR" was put together by a local "speed" shop. car is a 93 civic si with a BONE stock d15b7 swap with a stock p06 ecu. only "modification/change" was a 99-00 d16y8 tubular header.



what happened how i tried to get the car to pass.
1st attempt how the car was from shop running alright (no smoking so i said fuck it lets try this) NO CELS .i only changed out fresh oil, drained fuel system completely then filled up with fresh 87 octane CHEVRON gasoline (2 gallons) with 2 bottles of the red bottle (ISOHEET) failed smog high HC and VERY HIGH N0X
2nd attempt bought BNIB ngk zfr-5 plugs/wires, BNIB OEM cap/rotor, BNIB fuel filter put about 5 more gallons of 87 octane (chevron) replaced the catco (replacement cat) for a OEM cat. failed this time only HIGH N0X (NO CEL looped it nothing showed up)
3rd attempt put the first replacement cat back on(catco) as well as a known functional header cat that passed 2-3 cars within the year and my other car personally. SO THIS TIME IT HAD 2 cats on it i bought a BNIB 02 sensor and again failed ( HIGH N0X). something unusual i noticed was on a single decel i got a CEL 01 primary 02 sensor. i cleared the code drove it for another 10 minutes before heading to smog shop it did not pop up again. JUST ONCE after a decel. I looped the service port again during the 10 minute drive and (NO CEL's) showed up. is it possible to get a faulty sensor? or any other opinions of what could be wrong?

I was also thinking about taking my wideband & ECU out of the other car an putting it into this car to tune the afr's correctly so it will not be "LEAN" high n0x if that is the problem. or simply disabling the 02 sensor OPEN loop and see what happens








 

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NOx is a by product of high combustion chamber temps. In a nut shell your to lean.

 

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Discussion Starter #4 (Edited)
NOx is a by product of high combustion chamber temps. In a nut shell your to lean.


yeah but why would the engine be excessively lean? thats the part i cannot figure out.


Your cat might not be getting warm enough. It Dosent work right if its not.


]
i drove the car for a good 20-30 miles and roughly for 25-40 mins after reaching operating temp. before going to smog place








THIS IS NOT MY OLD 02 senor BUT IT LOOKS SIMILAR (not a clean burning mixture) if that makes any sense LOOKS LIKE A DAMN COW

 

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Honda Service News said:
NOx: The Know-How You Should Know Now For many areas of the country, NOx testing has (or will) become a major part of vehicle emissions testing. You can be sure that customers whose vehicles fail the test due to high NOx levels will be coming to your shop with questions. So even if you don’t have NOx testing equipment, you need to know what NOx is, what causes it, and how to reduce it.

What is NOx?

NOx (oxides of nitrogen) is a product of nitrogen and oxygen combining at high, sustained temperatures (2,500°F or more) inside the engine’s combustion chambers. NOx becomes a problem when it mixes with hydrocarbons (unburned fuel vapor) in the lower
atmosphere and forms that brown haze most of us are all too familiar with: smog.

What Causes NOx?

Many factors are involved in NOx production. High, sustained combustion temperature is just one. Here are some others:

Engine ping: Plain and simple, if the engine detonates (pings), it’s producing excessive NOx. As a general rule, if you correct the detonation, you fix the NOx problem. Over-advanced ignition timing: This causes detonation, so it’s a related cause of excessive NOx. Over-advanced timing creates an early buildup of combustion chamber pressure because the spark plugs fire too soon in the compression stroke. The still-increasing pressure ignites a secondary flame front inside the chamber that collides with the flame
front of normal combustion. The collision of these flame fronts is the “ping.”

Lean mixture: A lean mixture causes a higher than normal temperature in the intake air/fuel mixture, causing the preignition that produces high NOx. Any condition that makes the engine run lean may increase NOx.



Rich mixture: A richer than normal mixture won’t increase NOx, but the high CO (carbon monoxide) it creates will mask excessive NOx. Before you check the NOx reading, lower the CO level by correcting the mixture. Carbon deposits: If hot carbon deposits ignite the mixture before normal combustion begins, the resulting flame front collides with the flame front of normal combustion. The noise of this collision is preignition, and preignition causes excessive NOx.

Low-octane fuel: Low-octane fuel is more likely to detonate than high-octane fuel. If you use a fuel with a lower than recommended octane level, it can cause the detonation that produces NOx.

Fuel injectors: The altered spray patterns of dirty injectors can create hot spots in combustion chambers that increase NOx. A dirty injector causes more NOx because it increases the combustion chamber temperature. And dirty injectors reduce the NOx-lowering capability of the catalytic converter because they increase the oxygen in the exhaust.

NOx Control

A vehicle’s emissions control system reduces NOx two ways: during precombustion with EGR (exhaust gas recirculation), and during post- combustion with the TWC (three-way catalytic converter). By injecting a small amount of exhaust gas into the intake stream, EGR reduces NOx by lowering the temperature of combustion. The TWC then uses a reduction method to lower NOx even more. (The TWC also lowers HC [hydrocarbons] and CO levels through oxidation.) When it leaves the tailpipe, most of the exhaust gas has been converted to water vapor and carbon dioxide. On a healthy engine under load, the NOx level out of the tailpipe should be 200 to 600 PPM (parts per million).

How to Reduce NOx

To reduce NOx on a vehicle that fails an emissions test, do these 10 steps, in order:
1. Check the timing, and make sure it’s within specification.
2. Make sure the knock sensor and its circuit are working. A malfunctioning sensor can cause over-advanced timing.
3. Check the EGR system. Look for correct vacuum to the EGR valve and proper valve operation.
4. If needed, clear any clogged EGR passages.
5. Make sure the octane rating of the fuel being used is high enough for the engine.
6. Check the coolant, and add some if needed.
7. Check the cooling system (thermostat, cooling fan, fan clutch, etc.) for proper operation. If any of these parts aren’t working, they’ll cause excessive NOx from an overheated engine or high intake air temperature.
8. Check for dirty or clogged fuel injectors, and clean or replace them as needed.
9. Check the O2 sensor reading(s) for an overly lean mixture, and correct the mixture if needed.
10. If the previous steps didn’t reduce the NOx level, use a decarbonizer to remove carbon buildup in the combustion chambers.
 

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MIXTURE 15:1 20:1 Rich mixture: A richer than normal mixture won’t increase NOx, but the high CO (carbon monoxide) it creates will mask excessive NOx.

Am I reading this right?!?

15:1 - 20:1 is WAY LEAN! Why the F does it say Rich mixture??
 

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The only real way to figure out what is going on is to get a pre cat sample of the gases.

This will tell you everything you need to know. Can you get that?
 

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pull your o2 sensor and see what it looks like. I have failed smog because the o2 sensor wasn't throwing a code, but the o2 was fouled from running lean and the sensor was white and caked in carbon.
 

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MIXTURE 15:1 20:1 Rich mixture: A richer than normal mixture won’t increase NOx, but the high CO (carbon monoxide) it creates will mask excessive NOx.

Am I reading this right?!?

15:1 - 20:1 is WAY LEAN! Why the F does it say Rich mixture??

I may of copied and pasted wrong. It's on a PDF so it copied funny. I'll check it

EDIT: Fixed it. There was a picture in there that copied oddly.
 

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Discussion Starter #10
The only real way to figure out what is going on is to get a pre cat sample of the gases.


This will tell you everything you need to know. Can you get that?
how would i get that? maybe i am over thinking it


pull your o2 sensor and see what it looks like. I have failed smog because the o2 sensor wasn't throwing a code, but the o2 was fouled from running lean and the sensor was white and caked in carbon.

i had a "used denso (oem-type) sensor that looked like it wasnt burning right; it looked like a cow in other words random spots of black in areas. I REPLACED that sensor with a new sensor...
 

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Discussion Starter #12
The only real way to figure out what is going on is to get a pre cat sample of the gases.

This will tell you everything you need to know. Can you get that?
pull your o2 sensor and see what it looks like. I have failed smog because the o2 sensor wasn't throwing a code, but the o2 was fouled from running lean and the sensor was white and caked in carbon.
Are you sure the timing is correct? Stock b7 on a po6 should never fail. Is it possible the car has 190 injectors instead of 240?


that is exactly why i am shocked/pissed. i checked the mechanical timing and marks lined up correctly the distributor was dead in the middle @16 degrees so it did not appear to like it was off a tooth or anything the car doesnt feel sluggish or hesitant or anything weird. the ecu is 100% virgin 1992 1720 ecu board p06-a02. as for the 190cc injectors (the engine was "supposed to pass smog exactly how it was according to the one guy). everything was of a 1992 civic dx i would be surprised if it had 190's instead of 240s. i dont think you can tell just by looking at them? or can you??? does not run crappy i guess i can take pics of stuff
 

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190cc injector are OBD2 so you can tell by just looking at them.

190cc obd2:


240cc obd1:


See the difference in connectors?
 

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Get a timing light and check ignition timing. Too much adv spark will increase HC and NOX readings.
Remember to jump the service connection if you need to adjust it.
 

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That list is wrong. The Cx uses the same injectors as the Vx down to the part numbers 06164-P05-A00/2 and that list shows the Vx as 240cc.

I'm 99% sure that all obd1 D series injectors are 240cc's
 

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Discussion Starter #18
fuel filter is new just bought it 2 weeks ago. i already lined up timing marks and checked timing with a (bluepoint timing gun) but then again my friend was operating the timing light but he is "ase" certifed mechanic whom used to work at mazada and is a manager at autozone.. i can triple check the IGNITION timing myself- but i know for a fact the MECHANICAL timing is dead on with all the covers... and the cam should not be retarded or advance by a tooth... i am seriously confused this car runs good it just wont pass smog and i really DO NOT have an idea why.... i could only guess that the 02 i bought is bad or isnt the right resistance or something and that is making it "LEAN".... everything is stock/oem replaced i can think of/
 
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