beanbag

Hello folks,

I have a stock 97 GSR with 154,xxx miles on it. Over the last few tens of thousands of miles on it, the black soot problem on the rear bumper has been getting worse and worse. Just 2 days ago, I got a timing belt and valve adjust from the mechanic, where he claimed that the exhaust valves were all tight. Anyway, I think that is fixed now, but I still think I have a bit of soot out the exhaust. (Will need a few more days to see if it isn't just the remnants blowing out).

Anyway, a bigger problem is that it failed a smog test today. Here are the numbers from 2 yrs ago, and today:



Basically the NOx went from zero to fail, and the HC got worse also.

My first worry is that the cat didn't get hot enough. The car was somewhat warmed up, but then was off for about 5 minutes while waiting in line. Is there a way to tell from these numbers? Or how can I tell if the cat is hot enough? I asked the smog technician if a cold cat was a problem, but he didn't really know. You would think that the smog test places would have figured out this problem by now.

Second, I am not sure, but I suspect the soot on rear bumper problem might be related. I'm assuming the timing is correct, but perhaps the O2 sensor is going out?

Oh yeah, the car also burns about a qt of oil every 1-1.5k miles, but it has always done that, and never smokes, and the soot on the bumper is dry. The mechanic that did the timing belt change also poured in some oil stabilizer goo to try to reduce consumption. No idea if it is working yet.

Let's see...any other info... oh yeah, I ran the smog numbers thru one of those calculators, and it said my AFR numbers at 15 and 25 mph are 14.7.

All the internet reading I did point to either the cat or O2. How to tell which?

kchungb17a

Check your ignition timing first, but I'm inclined to think you need a new cat. Is it OEM?

beanbag

original cat.
I don't have a timing light, but I ASSUME that the ignition timing must have been set when they did the timing belt.

kchungb17a

Ignition timing is not typically changed during t-belt replacement. But if it hasn't been changed since your last smog check, I'd assume it's ok.

With high HC and high Nox together, my money would be on the cat.

eaglewesman

How did you end up getting NOx rating of 2 and 0 with an original cat that was 13 years old (2 years ago)? That's incredibly impressive, I've only seen those kinds of numbers when the smog test was performed right after a new cat was installed.

A new cat will for sure let you pass smog, however just because you pass with a new cat doesn't mean that a bad cat was originally the issue. Most of the time it's due to other underlying issues.

Things I've done to get my 93 to pass smog were running seafoam, adding alcohol to a nearly empty tank before testing, driving the engine on the freeway for 15 minutes prior to testing, adjusting timing, cleaning the EGR valve, basic tune up (plugs, wires, air filter, etc.) new O2 sensor, new cat

kchungb17a

Agreed, those NOx numbers from 2 years ago are ridiculously low. Evidence of a well running engine/emission system, perhaps? Or perhaps not since his HC numbers from 2 years ago are far above average.

And while it is rare for an OEM Integra cat to fail, it can happen. Passing emissions numbers are derived by a harmonious balance between engine performance and emissions system.

High HC typically indicates either excessive fuel enrichment or incomplete combustion. High NOx is a result of high combustion temperatures. The two do not usually coexist if it were not for a bad cat.

OP: you are running 91+ octane aka "premium fuel" correct?

beanbag

I usually run 91 octane, unless I accidentally hit the 87 button.

Yes, the NO from 2 yrs ago are really good. I looked at 4 years ago, and the HC was barely pass, and the NO was 121 and 11. However, I am not really worried about numbers that are barely passing. When I asked the smog tech about it, he said that a lot of times, what they do to save time is to wait for the numbers to come down as the car warms up, and then take the test right after it passes the threshold. I guess that's why a lot of the time, the 25 mph numbers are a lot better than the 15 mph.

On monday I will ask the mechanic if they adjusted the timing. Otherwise, I will have to get a gun or have them check it.

I don't remember if 2 yrs ago I made a special effort to heat the car up. I guess this time I was not as careful about it. I just assumed that whatever they do as a standard procedure should heat the car up enough. I looked at the smog test guidelines, and it said wait for the coolant temp to come to the middle, then idle another 3 minutes. I know this is not enough to get the car steaming hot to the point it makes clicking noises after you turn it off, but maybe the cat is already warm enough by then. Dunno

I wonder if all the soot I threw on the back bumper was bad for the cat. (Ya think?) I still need to see how much soot is coming out, and I still need to look into whether the O2 is bad or not.

I agree that I would rather fix the underlying issue, as it is probably cheaper than replacing the cat.

DeCePtEgRa

If it was a test and repair smog station they should of been able to tell you what's needed or what's wrong. If they were report them to the BAR.

Hit the cat with rubber mallet if it rattles cat is bad or with a infrared temp reader temp of cat at exit should be 100 degrees or 10% hotter than inlet temp. A new cat will make those numbers clean up.

beanbag

It was a test only station, so the techs are free to play dumb.

Good tip on checking the cat temperatures.

soulpwr

Soot indicates burning oil which will effectively lower octane but shouldn't affect the 4 gasses being tested. I'd check the spark plugs and try higher octane gas. Has anyone ever considered how the new ethanol blended gas affects emissions since it isn't as efficient as straight gas? That could possibly play a role in your issue

racebum

how much oil is the car burning? is it worse than a quart every 1500 miles yet?

beanbag

Like I said in post #1, it burns 1 qt every 1-1.5k miles. Which is either the same as usual, or maybe slightly worse. But the soot is dry, not oily. Currently there is oil stabilizer goo in the oil (put in by the mechanic coz he says it will help). I need to see if it has any effect or not. I cannot find the source of oil consumption and the compression numbers are good, so my best guess is stuck oil rings.

New spark plugs put in a week ago. Will it be too soon to tell their condition?

I cannot get higher than 91 octane unless it is race gas.

racebum

that's fairly common with older gsr engines. your oil burning is likely due to loss of tension in the rings, the guides and seals. the gsr/itr used a thin steel ring that didn't have a lot of tension to start with. over the miles and heat cycles they start to loose it. you basically wind up with race rings which can have great compression and make good power, they just allow some blow by. you can sometimes slow/stop this by simply doing a brush hone and installing new rings

the other problem you'll have is with the cat. burning that much oil will nuke a magnaflow cat within a year. only the oem cats seem to be able to resist oil burning and rich engines.

i had an itr that burned a quart every 1500 like clockwork. magnaflow cat lasted around a year before it melted

beanbag

How can I tell the difference between "loose" rings and "stuck" rings? I have read that Marvel Mystery Oil or Auto-RX can help the latter, but I doubt the former. Installing new rings is out of the question for now because that costs a lot of money.

I checked the O2 sensor today, and it seems to switch back and forth between rich and lean at an appropriate rate, so maybe that is ok.
https://honda-tech.com/forums/tech-misc-15/o2-sensor-testing-3094436/

DeCePtEgRa

Soot is from hc or hydrocarbons. Ever seen a diesel with a power tuner turned up get on it, hella black smoke and soot come out and left at tip of top stacks.

Also oil burning is blue smoke, fuel is black, and coolant is white.

vtaker

The numbers aren't that far off. I would give it a good hard drive and then go test again. Leave the car running while you wait otherwise the cat cools down too much.

If you still don't pass, buy a new cat and only use it for smog tests. Like people have said, an aftermarket cat in a car that uses oil will not last more than a few years. Unless you want to spend $700 for an OEM or buy a $200 cat every few years, this is your best bet.

DeCePtEgRa

I'm glad living 30 miles north other sac in attainment area so no nox testing and dyno.

el crapitan

few things.
first. high hc is caused by unburnt fuel. that's all. high co is rich.
second, i'm very inclined to believe the cat was not heated enough. below 500*f, the cat is inefficient in converting hc and nox specifically. a cat needs heat. plain and simple.
third, check your timing. after a t-belt replacement, timing must be adjusted. always.
the fact that you have both high hc and nox numbers really points towards too far advanced timing. that, or the cat was too cold.

if this were a customer car, what i'd do; check timing first. adjust as necessary. get the cat good and hot. take it for a rip on freeway. never shut it off prior if possible. that's about it. if that doesn't get the pass, would be time to dig further

el crapitan

also, if you're burning oil, keep the oil clean before testing. oil is dilluted with hc over time. it's a natural occurance. spent oil will effect your readings for sure

fcm

As mentioned, timing needs to be checked, [ign. timing].

Hows your gas milage, with those HC numbers I am guessing it is not so good.

Dry black soot, poor gas milage, high HCs, I would definatly check the ECT sensor. 94

DeCePtEgRa

Map sensor is higher up on the list of fuel control, speed density system is rpm and map sensor values, TPS then ECT, IAT and O2S

KILLAB17VTEC

easy man.u dont have to fix any prob.just move to different states,where theres no smog.

el crapitan

it's not a rich condition. high HC is caused by unburnt fuel. that's it. ie, misfire, timing, or possibly an inoperative cat. the fact that you have high NOx coupled with high HC leads me to believe the cat was not hot enough. or the timing is too far advanced. or a combination of both. too much timing timing will increase HC and NOx.
what you really want to see is your CO2 numbers and O2 numbers. those are gold.
a rich condition causes high CO, not high HC

fcm

That is why I asked if the fuel mileage was bad, we have replaced more then a few ECT senors on diff. MM&Y of cars.

Dry black soot is almost always due to a rich A/F, if a car gets poor gas mileage and has dry black soot at the exhaust the first thing I want to check is A/F ratio, and because older Honda/Acura ECT sensors do go bad, why would you not check the obvious, possible problem.

I did not say that The ECT sensor was the OPs problem, only to check it, unlike replacing expensive parts that may or may not be the problem it costs nothing to check the sensor.

There is way too much replace this and replace that to troubleshoot problems, it is so much easier/cheaper to test this and test that to eliminate things as possible problems.

With that said, it would not surprised me if the OPs problem is the cat, or timing, but I would also not be surprised if it was something else entirely, like maybe a bad ECT sensor.

So $200-$800 to replace a cat, $0 to test the sensor, I guess I will let the OP decide what he wants to "try" first. 94

BC2003UGA

rich condition means more fuel in mixture. and if you have a bad O2, you'd be running rich. if you have a bad sensor, you'd be running rich. if your car is throwing in CEL's, you'd be running rich. that's what cars with fuel injection do as a safeguard. factory programming says rich=safe and lean=bad. so it dumps more fuel if anything is incorrect, and down goes your fuel mileage.