SMKNTRS

This sucks, I have a feeling it is due to my TPI fuel pump causing it to run too rich. I am almost due for an oil change and haven't cleaned my air filter in years. I am not throwing any SES lights or anything unusual, wish I was brave enough to attempt the an adjustable FPR mod. If anyone has any ideas let me know. Here is the results of the test:

HC - 124 out of 117 = FAIL!
CO - .54 out of .65 = PASS
NO - 1535 out of 821 = FAIL!
CO2 - 14.6%

Note: I drove the car two hours on the highway and went straight to the testing center.

Thanks guys

akmusclecar

I am running a Holley 255lph pump without any problems. The diaphram in the TB FPR will compensate for the higher flow pump. I would first check for any vacuum leaks.

ownor

iTrader: (5)

imho the 160°F t-stat is hurting emissions badly if your prom is not setup for it. change out for a 195° and try again

+1 on ruling out the fuel pump, shouldn't be a problem with the tpi pump - the 255 though is a bit on the stronger side and might overflow the stock fpr/return lines.

acadburn

im not sure but i hear that if you make sure your car is good and warmed up first itll help lower the emissions. also if your car is running to rich you could always advance the ignition a little for the test ..... if you have monies to burn maybe a fresh set of cats how old are the ones you have on

SMKNTRS

The cat is only two years old and since I have no running issues whatsoever I don't see it being a leak problem.

One thing that might make it easier for the 160 thermostat is that my fan doesn't turn on automatically so I have a fan switch. So maybe insteatd of leaving the fan on i should just let it run hot when i hand them the keys. Could this 40-50 degree temp difference really make the HC lower by almost in half??

RFmaster

SMK

NOx emissions are the result of very high combustion chamber temperatures. NOx readings tend to increase dramatically whenever there are hot spots in the combustion chamber that exceed about 2400 degrees. Since you have stock engine high compression is not and issue, but having a lean mixtures will contribute to high chamber temps, as does over-advanced ignition timing. High combustion temperatures can also be caused by a lean fuel mixture due to faulty oxygen (O2) sensor.

High HC are indicative of incomplete mixture combustion. In a close loop operation O2 sensor reports back to ECM O2 levels. When cylinder misfire occurs unused oxygen gets dumped into exhaust where it is detected (assuming fully functioning) O2 sensor. If a single cylinder is occasionally misfiring ECM may not see higher O2 levels. Consequently exhaust contains unburnt HC along with excess O2. Over advanced timing may contribute to higher HC levels.

1) Inspect (be ready to replace with a fresh set) spark plugs.
2) Check for leaks in the EGR Valve and EGR control solenoid plumbing. Verify EGR is operational.
3) Check and verify ignition system (rotor, cap, coil, spark plug wires)
4) O2 Sensor - see if it is not lazy and actually swings above and below 450 when in close loop.

//RF

SMKNTRS

Hey RF, great info! Think I will do the plugs out of maintenance anyway. The EGR is actually MIA.. how can I monitor the O2 Sensor? With a scanner?

RFmaster

O2 Sensor can be directly monitored with DVOM (or DVM as some call it) or (better) with oscilloscope if you have access to one! Narrow band O2 sensor voltage has a range between 0 and 1 V. A new narrow band O2 sensor will have a cross count of 50 to 100 milliseconds (Apx. 1/20 of a second). A cross count is defined as a transition between rich (800mV) to lean mixture (200mV) and in reverse with 450 mV being stoich condition (14.7:1). Furthermore, TRL (time rich to lean) and TLR (time lean to rich) are not identical, but unless you are designing engine ECM control algorithms the last bit is rather meaningless. However, you should know that an old oxygen sensor may have a cross count as slow as 1/2 second even though it may sound fast, it is not fast enough! If the sensor has a slow cross count, the ECU is not receiving updates fast enough to efficiently manipulate the fuel flow through the injectors resulting in a sluggish fuel mixture response.

Scanner will not show real time voltage change as its update is very slow (160 baud).

//RF

topless89

the EGR is MIA? was there a visual inspection at the smog place... they should have cought it then. the EGR will definately lower combustion chamber temps if it is functioning properly. is your AIR system functioning?

RFmaster

Yes, EGR will reduce NoX substantially by reducing combustion chamber temperatures. AIR system on third gen primarily operates during cold start conditions to heat up capitalist. Thereafter, it is not used as ECM goes into close loop. As a side note on 95-96 B-body GM issued a TSB to disable AIR operation due to moisture ingress into the intake where it may damage MAF.
http://www.impalassforum.com/tech/en...p/air_pump.htm
95+ PCM's and associated emission system components are complex vs. what was used during late 80's!
You need to get that EGR back in auction, I am also surprised that you are not getting Code 43 (ESC, KS)

//RF

SMKNTRS

Update: I went back to the same testing place and had the car up to 210 degrees and I actually did worse than I did the first time with a temp of 120 degress. This time around my HC was 122.6 out of 117 allowable and my NO was 2230 out of 821 allowable. I really need to get this on a scanner to see what it going on.

I've tested at the same testing center before and passed without the AIR in place. There is no way I am going to replace the AIR tubes, I'd rather move outta my county. There is no visual inspection under the hood in my county also BTW.

SMKNTRS

ALSO! I am dumb, I was mistaking my EGR for something else, I DO HAVE the EGR in place but I am not certain about how well it's functioning. I just dont have AIR tubes

RFmaster

You have one or more cylinders misfiring which is indicative in higher HC numbers. As I have state before check your ignition system. Make sure that all cylinders are firing and you do not have any mis-fire! Do you have original CAT???

EGR valve is mounted on the passenger side of intake. Get a hand held vacuum pump and verify if EGR diaphragm is functional (i.e holds vacuum). If EGR holds vacuum - carefully remove EGR valve, and clean out carbon buildup in the EGR passages. Carbon buildup is very common in high millage vehicles which blocks this passage. Re-install, replace mounting gasket. Bring your coolant temperature down from 210 down to 185-190 range. Higher operating temperatures result in leaner mixtures which produce higher NoX numbers!

This is emission curve of a typical gasoline:

As you can see, stoich 14.7:1 is where HC and CO are both at minimal levels. Of course there’s not much you can do here about NOx, but as long as it’s not at its peak either which occurs at leaner mixtures! Being just a bit on rich side of stoich is better.

AIR is used to heat up CAT to operating temperature.

Basic background information:
http://www.ratwell.com/mirror/interro/techgas.html

//RF

SMKNTRS

Thanks for all your help, I would imagine I should notice a cylinder misfire right? These plugs I am using now also the cat have about 5k on them. I replaced these all at the same time when I put my headers on. I may just buy a new EGR since this one has 116k on it.

RFmaster

Spark plug wires are known to dry-up and cause a misfire as they age. Remember, that modern spark wires have build in resistance for radio noise suppression. Do not forget the other ignition components as well cap, rotor, and coil.

In a dark garage spray wires with a water mist from a spray bottle - if you see a blue glow or hear an engine stumble this will indicate a source of spark weakness and likely source of misfire. It does not take much to increase HC levels - one or two cylinders misfiring every so often.

//RF

SMKNTRS

UPDATE

Hey guys. Started working on getting my Camaro to pass emissions again. After replacing the EGR valve and replacing my vacuum line I was able to pass everything except the NO.

Reading/Limit
HC 60 / 117
CO .27 / .65
NO 886 / 821*

I failed the NO this time by 65 ppm. I sprayed the wires and looked for shorts and didn't see anything. I also tried a test again today using 93 octane like many places I researched suggested and it did a lot worse.

Reading/Limit
HC 117.4 / 117
CO .27 / .65
NO 1206 / 821

I don't know if I should replace my spark plugs along with cap and rotor. See about getting a chip tuned because maybe my mods are screwing with the emission system. Or run some seafoam hoping to clear things out.

RFmaster

What is your base timing, stock is 4 to 6 deg IFRC? NOx levels go up as cylinder pressures and temperature increase which happens when SA timing is advanced too much. When NOx levels are high HC levels tend to increase due to incomplete burn. Spark plugs, rotor, cap & wires - all should be in good working shape.

Try backing base SA from 6 deg down 3 deg.

//RF