car failing emissions NOx
a car in perfect shape, everything properly tuned and all sensors working, and EGR working properly is failing emissions on high NOx. everything else is passing....
using correct gas (but etested on both regular and supreme), using the correct plugs... EGR guaranteed to work and is not clogged. plugs read hot as well, as in the EGTs are too hot. correct fuel pressure. would a new catalytic be in order, or does a car with a bad catalytic converter fail on ALL tests?? in case you were wondering, the car in question is my old 93 saturn wagon twin cam 5 spd with intake header exhaust. |
Ignition timing too advanced. That's usually the problem with a high NOx rating. Unless it's digital ignition then, IDK :confused:
EDIT: Catalitics only deal with HC emissions normally. |
thats a tough one bruno..
nox is from high temperature combustion. What degree thermostat is being used? that could be something to consider.. is it running lean? a cat. oxidizess hc and co, not NOx. So your cat is fine. |
A failed thermostat that stays closed will give you high HC and CO reading; but if it stays open, perhaps if will give you this particular problem?
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If all else seems fine then it's gotta be running lean.
Throw in a new o2 sensor and it'll pass. They can't be that expensive for the Saturn since it prolly uses a 1 wire o2 sensor anyway. |
im sure he would notice the temp skyrocketing if the stat is failing.... On the other hand its a cheap and easy changed part thats never a waste of money....
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Originally posted by BoOsTd im sure he would notice the temp skyrocketing if the stat is failing.... On the other hand its a cheap and easy changed part thats never a waste of money.... |
O2 sensor and thermostat (dealer item, not aftermarket) are both brand new.
ignition is digital (coil packs).... I've considered all the easy possibilities already. I'm led to believe.... somehow.... that either carbon build up is causing increased compression (but with such high temps, it should have burned off), or that the injectors are in need of replacement. The techs on the saturn boards are also stumped. |
our wise friend google says the following:
Misfire condition Malfunctioning or improperly adjusted EGR valve Failed oxygen sensor Leak in exhaust tubing upstream of converter Excessive carbon deposits in combustion chamber Improper spark advance Blocked coolant passage Overly lean air-fuel mixture Damaged cold air duct Corroded or damaged engine sensor electrical connections because all the plugs look the same, I can eliminate the blocked coolant passage I think, and I know the car is not overheating... new rad, hoses, thermostat... and the fan is wired to be on all the time. |
wow..
my advice Bruno.. get methal hydrate, dump it in the tank and go for the e-test and pass it. or just retard the timing a deg. or two lol |
Originally posted by chris_si98 wow.. my advice Bruno.. get methal hydrate, dump it in the tank and go for the e-test and pass it. or just retard the timing a deg. or two lol vaccum leak is a possibility, is it the OEM EGR? if so take it out and clean all the carbon out of it, run a motorvac on the engine (cleans out injectors and all the carbon from the motor) try putting the stock air box back on, since its more restrictive it will make the car richen up a bit. what do the numbers look like? is it failing lots for NOx? and is it driving or idle test where its failing? |
If its carbon buildup...Take it for an italian tune up and see what that does.
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it's a dealer supplied brand new EGR valve and solenoid and vacuum lines. I replaced the entire system last year, and tested it many many times, it works (as in the ECU sends it signals and it does what it's supposed to). I've tested vacuum with a gauge, it indicates no leaks. I don't have the stock air box anymore.
I'll have to locate the emissions report for exact numbers... |
Originally posted by bbarbulo it's a dealer supplied brand new EGR valve and solenoid and vacuum lines. I replaced the entire system last year, and tested it many many times, it works (as in the ECU sends it signals and it does what it's supposed to). I've tested vacuum with a gauge, it indicates no leaks. I don't have the stock air box anymore. I'll have to locate the emissions report for exact numbers... |
Originally posted by 1PhatCX hmm too bad u dont have the stock air box, but definately find the papers and let us know man :) stutup wanabe mechanic:richslap: |
well what car are we dealing with here....I hate egr ****
anyway check for leaks on the intake side of things could be getting more unsensored air causing lean condition. maybe try putting a colder range of spark plug in there or new gapped plugs but I woudl throw a new o2 in there personally NOx is a bitch to get rid of sometimes but I woudl start replacing **** like o2 and check for leaks in intake system. |
thanks everyone for your input
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40 km/hr test
test limit reading HC ppm 75 37 CO % 0.42 0.05 NO ppm 0576 1517 Fail Curb Idle test limit reading HC ppm 200 42 CO % 1 0.04 NO ppm n/a n/a |
nox
how often do u drive the car? and when u do drive is it short trips ? What i did and I was in a similiar situation go to canadain tirew buy yourself some GTP ( guaranteed to pass) and foolow the instruction make your appointment and go for a really nice blast on the highway for about 1 half hour and have it tested nice and hot! let me know what happens
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Originally posted by dingus888 well what car are we dealing with here....I hate egr **** anyway check for leaks on the intake side of things could be getting more unsensored air causing lean condition. maybe try putting a colder range of spark plug in there or new gapped plugs but I woudl throw a new o2 in there personally NOx is a bitch to get rid of sometimes but I woudl start replacing **** like o2 and check for leaks in intake system. MAP reading (not MAF), therefore no unmetered air is possible. yeah, I gotta find out which ones will be colder, looks like a call to NGK is in order. O2 is new one other possibility I thought of was that the previous owner may have chipped it, which would advance timing of course, but the HC levels don't indicate a richer mixture which is also something a chipped ECU might exhibit. |
thats something i was gonna mention... did they get the cat nice and hot before the test? we sit and rev the car around 2500 rpm for 2 - 3 minutes before the test just to make sure its gonna work right
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yeah of course I warmed up the car before the test.... both times.
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they have some magical stuff I saw on the shelf at CT.. didn't really read it over too much but apparently it will guarantee you pass the e-test..
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