Failed Smog - Running Lean (Vacuum Leak?)

[Marccus]

1989, 360,000 mi.

First time failed smog and I failed it badly.

Smog Test:

15mph:
%CO2: 14.6 measured
%O2: 0.2 measured
ppm HC: 116 ppm max allowed, 31 ppm ave, 126 ppm measured (FAILED) :cuss:
%CO: 0.74 max allowed, 0.10 average, 0.12 measured (PASS)
ppm NO: 791 max allowed, 237 ave, 1228 measured (FAILED BADLY!) :cuss:

25mph (all pass)
%CO2: 14.4 measured
%O2: 0.0 measured

ppm HC: 91 ppm max allowed, 20 ppm ave, 91 ppm measured (PASS - BARELY!)

%CO: 0.62 max allowed, 0.09 average, 0.46 measured (PASS)

ppm NO: 730 max allowed, 199 ave, 535 measured (PASS)


I had a vacuum leak before from the coupling hose on the intake manifold and fixed it. I thought that solved the problem since the error codes on the O2 sensors not cycling and the lean fuel error went away.

But it seems like I must have a leak elsewhere.

But I am confused. Lean operation (leaking air) would cause high measured
O2, but I am reading 0.2% at 15 mph and 0.0% at 25 mph. I thought %O2 should be around 2.0%.

Lean operation would result in high temperatures which would lead to high thermal NOx formation. So that makes sense. I don't have EGR.

The leak makes sense since I failed at 15 mph but passed at 25 mph. At the higher mph, the intake air would dominate over the leaking air, whereas the opposite happens at idle or low mph.

Vacuum system questions:

I am totally ignorant of vacuum system. Is there a description or flow diagram of the system somewhere?

How is the vacuum formed?

Where does the vacuum "start"?

Where should I look for the leak after checking the coupling hoses?

Last time I squired WD-40 around the intake manifold I found the huge coupling leak. But there also seemed to be some oil being sucked in where the manifold sits on the engine. In other words the manifold may not be "sitting properly", although it seemed to tighten down OK and I put in new intake manifold gaskets.

I have a rebuilt, painted manifold ready to go in, so I could try that, but I would like to find the leak on this system.

Thanks.

 

[sdpatt]

Wow! A SHO with more miles on it that than mine! My non-EGR quipped engine has exhibited difficulty with the Texas emissions regulations that allow only a small percentage of increase over the very tight levels in Callifornia.


---------------Standard/Measured
Pollutant-----15 mph------25 mph
HC (ppm)-----128/37-------123/15
CO (%)-------.71/.16------.69/.08
CO2 (%)------NA/14.4-----NA/14.5
O2 (%)-------NA/4.1-------NA/2.4
NOx (ppm)----970/295-----878/189

I searched for all vacuum leaks and replaced the O2 sensors even without any error codes pointing to component failures. The only vacuum leak I was able to locate was in the charcoal purge canister vacuum line at the solenoid under the coil pack. This 3/16" line attaches to the throttle body on the upper, forward tap. With that leak corrected, the numbers moved closer to a passing grade, but still failed the NOx limit.

With all parts working at their best (I think), the engine was still unable to pass the test requirements on the NOx component. The values were about double the standard. The other values were well within their limits, including the HC and CO. Since the Gen I MTX engine in 49-state, non-EGR configuration was not designed to operate with NOx emissions as low as that required in California, you cannot expect the engine to pass those requirements.

The HC numbers your engine posted make me think that the O2 sensors are not switching as quickly as they should for optimum emissions and power levels. Tired, old O2 sensors do not switch quickly enough and cause the air/fuel ratio to be too lean and too rich for too long. The Bosch 13942 can be found at AutoZone for $39.99 each and is the direct replacement for the two OEM sensors on the 3.0L SHO engine. That fix may correct the higher HC emissions all by itself.

The final solution for the NOx portion was spelled SPOUT. With the 49-state version, defaulting to the base 10 degrees before top dead center on the igntion timing results in lower combustion temperatures that may be to only hope for those lower Ca limits. It makes the SHO run like a tired old dog (like your father's Oldsmobile), but it still drives to the test station just fine.

 

[Marccus]

Thanks scott. You directed me to the problem - the O2 sensors. I just installed them a couple of months ago, so I didn't even consider looking there. The wire was cut on the rear sensor. I don't know how that could have possibly happened since I didn't use any tools when I was on the ground under the engine that could have cut the wire. Maybe it came that way!

Now code 41 is gone and just 49 is left which states I have a SPOUT circuit problem. Can I ignore this code and not have any negative effects on engine performance?

Regarding SPOUT, what does that acronym mean?

On the emissions diagram, it talks about SPOUT and to disconnect the "inline connector" and attach something to measure something! I found a male connector hanging but it was blanked off with a special plug that could be easily removed. I don't know what this connector is for - attaching some sort of test instrument - but it certainly isn't inline.

If you have any more knowledge SPOUT circuit probkems or the emissions statements please advise.

Thanks.

P.S.

I'll try smog check again. If I don't pass, the state of CA says I must spend a maximum of $500 to try to fix the problem on NOx, before they will issue me my new registration!

 

[rangerj]

SPOUT = Spark OutPut of the ECU (electronic control unit) or DIS = Distributorless Ignition System. Do a search for "testing the DIS" and it may help you determine which component of the DIS system is causing a problem. Given the age of your car check all of the ignition systems electrical connections for proper contact and look for any corrosion on the connections or broken or shorted wires.

 

[rangerj]

Added thoughts; The vacuum is created when a piston is drawn down on the intake stroke like the piston in a needle syringe. Spray carb cleaner or WD-40 along the intake manifold gaskets to see if the fluid is drawn into the engine. If it is there is a failure of the intake manifold gasket. Otherwise, look for broken or cracked vacuum lines, especially at the connections.

 

[hawkeye18]

agh, don't go yet! that connector you found, was it right below where the computer test connector is? by the passenger side strut tower? If that's the one you found, PULL THAT CONNECTOR! That's the SPOUT (SPark OUT) connector, pulling that will force your engine to -10 degrees. Like sdpatt said, it will make your car run like shee-ite, I mean CRAP, but it will significantly lower emissions. It should be grey (sometimes black, sometimes white), have two wires coming from the bottom, and have a plug you can remove. Keep that plug tho, you'll need to put it back in when you're done :grin:

 

[Marccus]

The connector you describe is the connector I found.

I don't understand what you mean by "PULL THAT CONNECTOR". It has a plug in it and is just hanging.

I left the plug in.

Do you want me to pull the plug out? But what will that do, unless the plug is a shorting plug connecting the two terminals inside to complete a circuit.

I did pass emissions, but I am at the maximum - right on the line - for CO and HC. I passed NOx, as now the cylinder temperatures are lower with the engine not running lean, reducing thermal NOx.

The technician thinks I need new cats. I have had the PP Plus high flow Y-pipe installed for about 10 years now. The exhaust does smell "richer" than it should be, like a presence of HCs.

The presence of high HCs and CO does indicate to me that the cats are no doing their job.

I spoke to PP once about this and I think he stated the cats are from Magnaflow.

I have to smog again in two years, and I doubt I will pass then no matter what I do!

So I can look into welding new cats in between now and then.

Thanks.

Let me know what you think.

 

[SHOtimer]

The plug in the middle of the SPOUT plug is exactly what you said, it is a short connecting the two sides. By pulling it out you set the default timing at -10 degrees, and greatly reduces all of the emissions outputs.

Doug

 

[Paul]

I donno