'95 Saturn SL2 man trans Calif. emissions problem

billr

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#1
Well, as usual I put off the smog test until the last minute, but unlike usual it didn't pass. HC is low (1&2) and CO is lower (0&0) at the 15&25 mph test speeds. NO, though is way up, about 2000 at both speeds. I checked the plugs last night (before test) and they look very good. Compression is 180-210 on all cylinders, not as even as I would like, but it has 240K miles on it... It runs fine, of course. The cat is a "know good" one, so I am focusing on the EGR valve. This has a linear EGR valve with the 5-pin connector up on top. I changed one on a different SL2 a few years back, and even took the old one apart to see how it was constructed, but don't know where it is now. I remember there being a linear pot and a big magnetic "voice coil" in there. Does anyone have a pin-out of that EGR valve so I can start testing it? Any other suggestions besides the EGR system (yeah, I know that includes the passages under the valve)?

Edit: I do have an MT2500 that shows live-data for this OBD1 car, but it only shows EGR as being "on/off". Sitting still it is always off, no matter what the engine speed. I will take it out for a drive to observe the EGR action as soon as another driver gets home.
 
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#2
I am confused- low HC and CO is good -yes? this is a 1.9l?
you failed for Nox only?
Can your scanner command EGR open?
I remember that some vehicles a VSS signal was needed to have PCM command EGR...
 

billr

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#3
Well, while driving the "EGR Solenoid" status stays off. And, more to the story: When I first took it for testing there was an exhaust leak between the header and pipe going down to the flez, the three-bolt flange wasn't properly tightened. It wasn't too bad, but was a noticeable noise. Since it is below the (only) O2 sensor I was hoping it wouldn't affect fuel trims and emissions much. Since gasses there are well below NOX-forming temperatures, I sure wouldn't have expected the extra air to increase NOX. With the exhaust leak is when the NO was 2000, I don't know what the NO was after that leak was eliminated, I was just told that it failed again.
 

billr

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#4
Yes, it's the 1.9l DOHC, both HC and CO were very low, only the NO was way high. Unfortunately, the Snappy won't command the EGR, I'm lucky that it even connects to this OBD1. There is some confusion about whether Saturns of this era have classicall vacuum-operated EGR valves, or electric "linear" ones like all of mine have. So the Snappy may be oriented towards the vacuum ones and the fact that the "solenoid" is never commanded on may be meaningless.

Edit: Speed read-out on both the dash and Snappy are fine, so I think the VSS is OK.
 

billr

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#5
More info:

Thanks, I kind of figured out the pin-out using an ohmmeter, but I didn't know for sure which pins are ground (hadn't look at harness yet). The valve and head ports are clean, the valve pintle moves easily manually. The pot is linear, and the pintle moves linearly in response to a varying voltage applied to A and E. Back on the car, applying that varying power to A and E starts bogging the engine down (idle) until it dies when EGR voltage is 7.5VDC; upon restart the idle is high at first, indicating the IAC was struggling to compensate for the EGR action. Next step is to make a break-out-box to see what is happening there while driving. I see the EGR "controller" scabbed-on to the harness just under the RH side of the battery. The CEL hasn't been on but did come on, of course, when I had the EGR disconnected to power it manually. Four codes were set in history, 32 (EGR fault), 52 (???), 53 (system voltage error), and 83 (???). Any hints as to what the 52 and 83 are?

I am working two forums at once with this problem, with a lot of cut/paste to save typing; so some of my replies may seem odd. Please ask for clarification if you need it.
 

billr

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#6
I'm getting to know more about these EGR systems than I intended. Apparently the electric EGR valve was a "scab-on" then, with a "controller" in between the valve and the PCM, the controller is just taped to the harness. Maybe they were getting ready for OBD2? Does anyone have a test procedure for that EGR controller, or the system, or a schematic of the whole circus? As stated above, I am certain the valve itself is OK, so if it isn't opening it has to be a problem with the wiring, the controller, or the PCM. When I get the break-out-box in place I will know more (I hope!).
 

billr

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#8
What in the world is that picture of??? Nothing that I know of on the Saturns...
 
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#9
Secondary Air Injection Pump

Secondary Air Injection Pump
Volkswagen Jetta IV VR6 24v
Keep your engine running efficiently

The secondary air injection pump injects fresh air into the exhaust stream to help burn off harmful pollutants in the catalytic converter. If the injection pump begins to fail, since it is a vital part of the emissions system, a fault code will be triggered. The air flow from the pump will be too low to properly mix with the exhaust stream to clean the air traveling through the catalytic converter. By simply replacing this pump efficiency can be restored and there will be no worry about failing an emissions test.
 

billr

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#10
The air pumps started being used in about '66, for reducing HC and CO (both near zero, in my case here). They have been phased-out in most cases, as the cat does the same and more. No air pump on this Saturn. I assume Dan is joking...
 
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#12
I like dans thinking- F'em inject excess clean air into exhaust before tailpipe would skew the sniffer readings.... I will bet the old school hot rodders do this routinely.

ANYWAY the linear EGR for that year must be CALIF only a bitch to find info... let me know if dia helps.
 

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billr

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#13
Actually, Dan's schematic was more useful; now I have pin-outs for the "Linear EGR Module". The EGR valve itself isn't the bitch, it's that damn "module". I have found no listings for buying it, if it comes down to that.
 

billr

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#14
Alas, the dead-line is coming up fast; I need to resolve this soon! I did make a break-out-box for the EGR valve, and tried it on all three '94/95 SL2 Saturns that I have. The results were the same on all three, once the engine warms up the valve drive signal and the pot feedback signal were fairly close on the three cars. And, I know that the EGR valve is really "EGRing" on the one failing NOX; if I command it open, electrically and through the wiring harness, the engine responds appropriately by gagging with loss of power or dying at idle. Any comments on whether the (now fixed) exhaust leak could have affected NOX so severely? I don't have any test numbers after that was fixed, but am doubting it could have been so drastic, and was reluctant to spend my free "retest" until I had checked out the EGR system. Since that appears OK, anything else I should look at? I did compare (commanded) ignition timing on two of these cars while driving, looks to be the same and both drive the same (nicely). In short, the cat is nearly-new, the HC and CO are very low, the EGR seems to work; what else can I look at for very high (2000 ppm) NOX???
 
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#15
240K miles on the engine? Do a before and after compression test with a decarbonizing the engine in between. Excess carbon will increase combustion chamber temperatures. Another cause is increased thermoconductivity between the combustion chamber and the cooling system. Cooling system could stand a good flushing.

Owned a California car once, what the heck is that thing under the hood? Was an air injection pump, injects air into the cat. Are they still using these?

See labels on my Christmas tree lights, the insulation causes cancer in rats in California. Hope this doesn't hurt my Wisconsin rats.