Failed Emissions again!

[lithiumus]

So it's been 2 years since my last emissions test where I had some issues...

http://www.nsxprime.com/forums/showthread.php?t=48432

Similar failed results this time. The load test at 2500 RPM passed with flying colors

HC 18 ppm
CO 0.0
NOX can't remember

But it failed idle big time

HC 1460 ppm
CO 0.2

Parts...
O2 sensors - 2 years old
Cats - known good (2 sets)
PVC valve - 2 years old
Oil - 2 weeks old
Spark Plugs - 1 years old
vacuum hoses - 1 year old (replaced all emissions hoses)
Fuel Injectors - serviced by RC Eng 1 year ago
Fuel Filter - 1 year old
Throttle Body - serviced 2 years ago
New Throttle screw
Ignition coils fall within resistance specs

The last time the Acura service manager twiddled with the idle after I spent over $1,000 trying to locate the problem and it miraculously passed. Not sure what fixed it but now it's dumping fuel again during idle.

I might hook up my AEM wideband from my Accord and see what the readings are at idle but I suspect that with those numbers, AFR is likely 11 or lower...

I've tested the temp sensor that tells the ECU that the car is warmed up and it is inline with the chart in the service manual. I suppose I could go as far as to test those wires @ the ECU to ensure that the ECU is receiving the signal as well...

Any ideas? Is there something at the throttle body or EACV that could cause this rich idle condition? Not enough Oxygen let through by the idle valve or fast idle valve? The idle is fairly stable at around 770 - 800...

I can probably do some troubleshooting if I have my wideband showing the idle AFR. What should I fiddle with? Thanks in advance.

 

[nsxotic911]

Someone on the forum once proposed Auto-RX and I tried it on a Civic that had a CEL for failing cat converter. Although it didn't fix it for good, it fixed it just enough for it to pass emissions - and just as I was getting out, it came on again :biggrin:

Give it a shot. It's available at autozone or online.

 

[sojusoulja]

i'm sure your smog guy did this but make sure that your car is warmed up sufficienty...go drive it hard for a while before testing.

 

[lithiumus]

I did use a bottle of this guaranteed to pass stuff. I filled 3/4 tank and put this stuff in, use up to 1/4 tank and filled up for the test.

The car was warm and was idling on the dyno for some time. The emissions tests in Canada force you to perform sustained load on the car to prepare for the test.

I'm guessing there must be something mechnical that is awry rather than luke warm cats considering when I passed last year my HC was only about ~80 and this time it's 1480! Even when I failed last time my HC at idle was only 850 and 740.

 

[nsxotic911]

I did use a bottle of this guaranteed to pass stuff. I filled 3/4 tank and put this stuff in, use up to 1/4 tank and filled up for the test.

The car was warm and was idling on the dyno for some time. The emissions tests in Canada force you to perform sustained load on the car to prepare for the test.

I'm guessing there must be something mechnical that is awry rather than luke warm cats considering when I passed last year my HC was only about ~80 and this time it's 1480! Even when I failed last time my HC at idle was only 850 and 740.

Did you use Auto-RX or the 'other stuff'?

 

[Daedalus]

Cats work well if hot enough, but not at all if less than hot enough--same as O2 sensors. The idle valve is not the culprit. The car needs to adjust the fuel to match the air, not adjust the air to match the fuel. Either there's a fuel leak or the car's dumping the fuel on purpose. Fuel leaks are rare. If you were to measure both O2s you would at least know if the problem is isolated to one bank.

 

[lithiumus]

Did you use Auto-RX or the 'other stuff'?

I used a Penzoil emissions guarantee. Mind you, 2 years ago I didn't use anything and after the service manager fiddled with the idle, it passed. But that definitely sounds like an intermittent solution to another problem.

 

[ak]

If it's running rich, one thing could be the fuel pressure regulator is faulty, or maybe the vacuum tube to it is disconnected. It's probably a long shot since I've never heard of it going bad but it's easy enough to test. Check out 11-95 on the service manual.

-ak

 

[lithiumus]

Cats work well if hot enough, but not at all if less than hot enough--same as O2 sensors. The idle valve is not the culprit. The car needs to adjust the fuel to match the air, not adjust the air to match the fuel. Either there's a fuel leak or the car's dumping the fuel on purpose. Fuel leaks are rare. If you were to measure both O2s you would at least know if the problem is isolated to one bank.

hmmm... if there is too much air, the car is going to try to match the fuel right? of if there is too little air, the car will cut fuel but only to a point to ensure the car doesn't stall...

Maybe it's the evaporative system malfunctioning and purge solenoid is releasing too much fuel at idle... We had the car running for over an hour because the RPM sensor of the emissions unit had trouble picking up the signal. The cats were kept hot the entire time.

I'll verify the O2 sensor signals and use my wideband but I can't imagine the O2 sensors malfunctioning when the high idle / load test worked perfectly. It must be something in the idle system or evap...

 

[lithiumus]

If it's running rich, one thing could be the fuel pressure regulator is faulty, or maybe the vacuum tube to it is disconnected. It's probably a long shot since I've never heard of it going bad but it's easy enough to test. Check out 11-95 on the service manual.

-ak

Thanks AK, another item to add to the list to check. I did replace the vacuum hose to the fuel regulator and I'll double check the connections. Strange that it's running rich just at idle...

 

[FastraxTurbo]

High HC is caused usually by a misfire. If your CO is high as well, it could be a rich misfire, but since it is low, it is usually a lean misfire.

 

[drew]

this stuff is a nightmare to figure out. You may have to invest in an ECU extension harness and data logging system (~$1K) so you can figure out what is going on, it would be worth it because the dealer will never figure it out.

The extension harness is important so you can easily label, tap into the ECU without harness damage and easily see what is going on *at the ECU*.

Here would be my plan of attack:
#1 Cooling system. I would guess the system is or *thinks* it is running cool and hence the richness at idle. You might even have a thermostat that is stuck in the open position. Marginal temperature sensor

#2 fuel delivery (pressure, purge, o2 feedback)
#3 air mixture (TB, map and all that)

 

[Sulley]

If your car was just idling or revved up with no load while the tech messed around, then your cats weren't at operating temp. There just isn't enough load to keep them hot, after you stop driving the temps drop in just a few minutes.

The HC is very high and there may well be something wrong other than the cats not being at operating temp. If there is no penalty for multiple tests then I would try again with the cats hot. Maybe with a tech who knows how to use the equipment.

 

[lithiumus]

I just spoke to the Service Manager who fixed the problem last time. He indicated that all he did was raise the idle to fix it last time. He asked me to leave the car with him tomorrow so he can work on it.

Well he can put it on the Emissions Dyno in test mode and can confirm this. (without penalty, just costs me more money...)

The idle test is performed immediately after the high load test. The emissions forces you to keep the reves at 2500 for about 2 minutes to prep then does the test immediately after for about 2 minutes, then you drop right into the idle test. If the HC was 250 or 300, I'd say maybe the cats were not warm enough... 1480 tells me somthing is wrong...

thanks again Drew. Those sound the like the most logical things to check for. If the Service Manager is unable to figure it out, I'll use my wideband to monitor idle and probe the ECU and see what the sensors say at idle and try to make some sense of it...

 

[BioBanker]

Garrick- my car passed last week no problem and I ordered my sticker on line. Never during the process did it ask me for my sticker number of drive clean number. Sticker arrived in the mail today.

Dont know if they've linked the online renewal to the drive clean sites, but I HIGHLY doubt it.

Id give it a try and see if your sticker shows up.

 

[lithiumus]

I processed it online last night and it might not be linked but I also think that the timing on my emissions is off... I may not need emissions this year. I tried to do a 2 year renewal but it indicated that my car is not eligable for a 2 year renewal (likely due to emissions). If I get the emissions done this year it's good for 2 years and I might be able to leap frog a year...

Either way I dropped the car off and asked the Service Manager to not spend too much time on it. If what he did last time doesn't work, just leave it and don't retest.

If my sticker shows up (I'm out of town anyway until the 13th) I'll have another year to figure this out and I'll follow some of the suggestions above and try to find the root cause... it's all about the datalogging and Acura won't be able to do it or at least not for cheap...

 

[Synthesis]

I processed it online last night and it might not be linked but I also think that the timing on my emissions is off... I may not need emissions this year. I tried to do a 2 year renewal but it indicated that my car is not eligable for a 2 year renewal (likely due to emissions). If I get the emissions done this year it's good for 2 years and I might be able to leap frog a year...

Either way I dropped the car off and asked the Service Manager to not spend too much time on it. If what he did last time doesn't work, just leave it and don't retest.

If my sticker shows up (I'm out of town anyway until the 13th) I'll have another year to figure this out and I'll follow some of the suggestions above and try to find the root cause... it's all about the datalogging and Acura won't be able to do it or at least not for cheap...

so you took it in, he messed with the idle screw and charged you a grand??
do you know for sure that last time he didn't just give you the sticker?

that's the only good thing about alabama..... no emissions. you can drive your car on fire, and it's legal.

 

[lithiumus]

so you took it in, he messed with the idle screw and charged you a grand??
do you know for sure that last time he didn't just give you the sticker?

that's the only good thing about alabama..... no emissions. you can drive your car on fire, and it's legal.

In the end yes, but at the time they suspected O2 sensors, Cats, Throttle body cleaning, PVC, etc. I was there watching my car on the emissions dyno. The emissions facilities are directly connected to our DMV so the results are immediately sent. If it fails, they know, if it passes, the DMV will issue the sticker but not before...

 

[lithiumus]

I got the car back today and they couldn't get the idle HC low enough to pass. They were able to get the HC down to ~250ppm from 1,480ppm by raising the idle RPM. They only charged me the failed emissions test $37.

Looks like I have some emissions troubleshooting to do...

 

[D'Ecosse]

Hi Garrick - sorry for your woes
High HC is definitely a sysmptom of misfire - HC is unburnt fuel so could also be overly rich condition.
Since higher idle speed seems to helpa little, might be worth changing out the 02 sensor - if it is off it may be trying to incorrectly adjust for what it thinks is a weak misture & dumping more fuel in.
One thing you could do right off the bat is to do a baseline, then unplug the clock fuse to reset the trims & see if there is any immediate impact to the HC reading.
Next thing in line (or maybe first) would be the coils &/or plugs. Are any of the cylinders contributing less power? Try disconnecting each one at a time & see if you have a low power cylinder - it will have less effect on the idle if you inhibit a 'low' cylinder vs a good one.
If you find a weak cylinder it could also potentially be the injector - could be passing a weak enough mixture to not fire, yet still enough unburnt fuel to give the high reading.
Once you find & eliminate the problem, your cat on the manifold with the problem is most likely shot - they don't like raw fuel being dumped over them for prolonged periods so prepare to change that too.
Plugs/coils is most likely source
Good Luck - hope those suggestions help!

 

[lithiumus]

Super old thread I know, but I figured I would close out my open issues in case there were searches, etc. In the end it was simply the AIT sensor that needed replacement which was something that was discovered to be a common cause for Idle HC dumping of fuel around 2012. Drew was on the right track in the logic and the engine was definitely seeing incorrect temps and compensating with more fuel at Idle.

Compounding the problem was the fouling of the spark plugs due to super rich idle and incomplete burns during idle. As the newer thread indicates, I may still have a vacuum issue, but not enough to fail emissions.

http://www.nsxprime.com/forum/showthread.php/159564-Is-your-NSX-failing-smog-Read-this

My most recent passed emissions results...

My 2500 rpm results were
HC Limit = 200, Reading = 25, Pass
CO Limit = 1, Reading = 0.01, Pass
Dillution = 12.55

Idle results were
HC Limit = 200, Reading = 170, Pass
CO Limit = 1, Reading = 0.02, Pass
Dillution = 12.77

 

[darock]

HC 170? There must be something wrong still ...

I had my NSX tested before I bought it and it was reading HC 77 but the car does NOT have cats right now!

So 77 without cats

Bernhard