Northstar Wont Pass Smog Emissions

[MCD0MINGUEZ]

Vehicle: 2001 Cadillac Deville
Promblem: Failed Smog Emissions Test [HC (PPM) MAX=31 MEAS=50]
Recent Services: New Spark Plugs, Air Filter, Oil Change, Throttle Body Cleaning, Inspection of Idle Controllers.

Does anyone have any ideas what could be causing my car to fail? I've been having ENHANCED SMOG INSPECTIONS, would it pass if I have a standard smog?

[carnut]

Car not reaching temperature i.e. thermostat weak. car should run 205 to 220 degrees. EGR passages plugged? but I think that affects NOX more than HC. You can monitor temp thru the on board diagnostics. Should reach 95 to 98 degrees celcius in just a few min. Slow to react pre cat. OXY sensor. Again, it can be monitored thru on board diagnostics. I've seen a thermostat affect operation ( delay of going into closed loop) of the OXY sensor, so verify engine temp 1st.

[MCD0MINGUEZ]

All my Emission Control Systems passed according to my visual/functional check results.

But my ASM Emission test failed at 25 mph [RPM 1121, %CO2 14.8, %O2 0.1, HC (PPM) MAX 31 AVE 4 MEAS 50, CO (%) MAX 0.43 AVE 0.01 MEAS 0.11, NO (PPM) MAX 687 AVE 18 MEAS 24] FAIL

Also my 15 mph HC (PPM) test barely passed at MAX 47 AVE 4 MEAS 47

[submariner409]

Hmmmm........Thought your car did not need the dynamometer test, just an OBD-II plug-in go/no go.

Do you have a Service Engine or any DIC messages concerning transmission or gas cap ?

Pull your Diagnostic trouble Codes from the car's built-in scan system. You don't need a scanner or outside help. Use the sticky thread at the top of this main page titled "How to pull codes", scroll to the OBD-II procedure, and then use the links to the P,B,U, and C codes to find what each (if any) means.

Curious that the car did not throw a "Traction Disabled" message and fail everything. (All wheel speeds not within tolerances for Stability Control.)

[MCD0MINGUEZ]

The car had an IDLE ERROR code appear a week ago, I took it into my local Dealer and they fixed the problem (Idle Screw Too Tight). Now there is no codes or lights appearing on the dash.

The first 2 smogs I had done were enhanced with dyno's. If I register it in Santa Barbara County first before I smog it again they, will perform a normal smog this time. Would my car maybe pass a regular smog test?

[00 Deville]

That's odd... I've never heard of an OBD 2 car ever getting anything other than just checking the computer for no codes and a ready light... I never lived in Cali either.

[jcresciSTS]

I didn't watch mine car get smogged because I had to walk and get the money for it but it did take about 15minutes to complete which leads me to believe mine wasn't with the OBD-II either, I went to a standard smog check too.

[MCD0MINGUEZ]

It still hasn't passed smog yet. Also the idle codes returned. P0506 idle too low and P0507. When I try to start the car the RPMs drop below 600 and shuts off. Would this have anything to do with why my car isn't passing smog?

[Caddyshack100]

Those codes, will not light the MIL until the second time, they are both considered GM B codes in the sense that they do not affect emmissions right away like an o2 sensor would which is a A code. To properly diagnose these codes, you will need a BI scanner in order to control the IAC valve. It sounds like you have done the right things.

Conditions For Running the DTC
DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0335, P0336, P0340, P0341, P0385, P0386, P0401, P0403, P0404, P0405, P0440, P0442, P0443, P0446, P0449, P1106, P1107, P1111, P1112, P1114, P1115, P1121, P1122, P1336, P1372, P1404, or P1441 are not set.
The engine coolant temperature (ECT) is greater than -40°C (-40°F).
The intake air temperature (IAT) is greater than -18°C (-1°F).
The ignition voltage is between 10.5-16 volts.
The barometric pressure (BARO) is greater than 6 kPa.
The engine run time greater than 40 seconds.
The transmission gear state has not changed for 3 seconds.
The torque converter clutch (TCC) state has not changed in 3 seconds.
The TPS less than 1.5 percent.
The spark advance is less than 12.39 degrees.
The spark retard is greater than -13.79°.
The vehicle speed sensor (VSS) is less than 3 km/h (1.9 mph).
The above conditions are present for 3 seconds.
Conditions for Setting the DTC
The actual engine speed is 100 RPM less than the desired engine speed.
The above enabling criteria must be met and fail the diagnostic 3 consecutive times to set this DTC.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
Inspect for the following conditions:

A restricted air intake system
Proper operation and installation of all air intake components, for example, collapsed, clogged, or loose air intake ducts, a clogged air filter, and proper operation of the mass air flow (MAF) sensor, if equipped
A tampered with or damaged throttle stop screw
A tampered with or damaged throttle plate, throttle shaft, or throttle linkage
Objects blocking the IAC passage or throttle bore
Excessive deposits in the IAC passage or on the IAC pintle
Excessive deposits in the throttle bore or on the throttle plate
Vacuum leaks
A low or unstable idle condition could be caused by a non-IAC system problem that cannot be overcome by the IAC valve. Refer to Symptoms - Engine Controls .
If the problem is determined to be intermittent, refer to Intermittent Conditions in Symptoms.

[submariner409]

Pull the IAC (Idle Air Control) valve out the side of the throttlebody and clean it with TB cleaner. Clean the TB as posted several times in here, Seville, Northstar Performance and technical down below.

"Idle screw too tight" ?????? No idle adjustment screw on a 2001 that I know of...........

[MCD0MINGUEZ]

I did clean the areas myself and the car idle seems to be fix! The idle is staying around 775-800 and there is a slight rough idle but at less the car is staying on. Now what should I do next to pass smog?

[submariner409]

Your idle, in D, should be about 650 rpm.

When you removed the IAC to clean the tip, what did it look like?? Nasty black or clean ???

If it was nasty, then you need to go back and carefully remove the intake ducting, block the thottle wide open and use throttlebody cleaner, rags, and a toothbrush to scrub the butterfly (both sides) and TB bore until they're absolutely clean. Stuff a lint-free rag into the TB past the butterfly in order to prevent liquid cleaner from pooling in the manifold. Remove the rag carefully with long needlenose pliers. .......or be very careful with the amount of cleaner you spray/use.

You may also want to remove the EGR valve, just behind the throttlebody, and scrub that and the gas passages also. A dirty/stuck EGR will screw up an emissions test, too.

[carnut]

I've seen no response about engine temperature getting to 95 degrees C ? within 10 minutes. You ask what else you should do and I for one cannt respond unless I know this reading. How many miles on this car?

[submariner409]

mcdominguez,

95C is 203F. Normal Northstar everyday temperature.

F = C x 9 / 5 + 32

C = F - 32 / 9 x 5

As carnut posted, your engine should reach 200F within 2 miles or so - a few minutes of town driving.

EDIT carnut, are you looking at the possibility of the engine not going to closed loop ?

[carnut]

Yes exactly, or going into it then out during the test.