1995 Saturn SL1 fail Emissions Test for high NOx Car: 1995 Saturn SL1 SOHC, 1.9L. Symptom: Drive Clean Emissions Inspection Report show failed reading for NO ppm: Another headache.... ok my Saturn is 14 years old, so things are bound to fail on it. I’ve included my last three Emissions Tests results below, (done every 2 years). In 2006 my NOx result was a close pass. In 2008 the result for NOx was a bad fail. However the HC and CO measurements have not been a problem. The info included suggests for high NOx on driving test... 1.-inoperative EGR... my EGR valve is fine, not the original, I did replace it with a new one 4 years ago. 2.-excessive lean air/fuel ratio... I did replace the air filter 2 months before the test. I have used fuel injector and fuel system cleaners over this year 3.-malfunctioning catalytic converter - 3-way catalyst only.... this is possible with the age of the car, but I would think that the HC and CO readings would be higher too? There is good exhaust out of my tailpipe, so the cat is not plugged. I did not measure the pipe pressure before and after the cat though. 4.-excessive spark advance... I change the spark plugs myself, gap them properly at 0.040”, the current four are one year old, Champion brand RC12YC, traditional flat copper core. I do not use platinum or iridium plugs. 5.-faulty thermostatic air cleaner system.... air filter is new, I did clean the throttle body valve this summer. 6.-engine deposits or mechanical defect..... my engine runs and idles well. I do oil changes every 5000 - 7000 Km, mostly highway driving. This past summer I did do a mild engine flush using 1 L of ATF transmission fluid before an oil change. Folks have recommended this over concentrated flush chemicals, never had problems. 7.-faulty cooling system... I did replace a failed water pump in September, coolant was flushed and replaced. I did replace my accessory belt. I also replaced a faulty temp sensor in July’08. The pigtail harness to this coolant temp sensor was corroded and caused running problems with my engine 2 weeks ago (stalling). I was stranded out of town when this happened and took the car to a shop where this pigtail harness was replaced. Engine was running fine thereafter and this 2008 Emissions Test was performed at the same shop immediately after the repair. Any suggestions? .... Much appreciated. Thanks, Roger Three Emissions Tests results... -------------------------------------------------------------------------------------------------------- Results: Nov 2008 HC ppm @ 40Km/h ASM 2525, 23, limit 75, pass; @ Idle, 53, limit 200, pass CO % @ 40Km/h ASM 2525, 0.01, limit 0.42, pass; @ Idle, 0.00, limit 1, pass NO ppm @ 40Km/h ASM 2525, 1149, limit 576, FAIL; @ Idle, -, limit -, - (not done) @ 40Km/h RPM 1780, Dilution 14.41, valid @ Idle, RPM 745, Dilution 12.80, valid Analyzer Software Version: 4.54 -------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------- Results: 2006 HC ppm @ 40Km/h ASM 2525, 7, limit 75, pass; @ Idle, 20, limit 200, pass CO % @ 40Km/h ASM 2525, 0.01, limit 0.42, pass; @ Idle, 0.16, limit 1, pass NO ppm @ 40Km/h ASM 2525, 550, limit 576, pass; @ Idle, -, limit -, - (not done) @ 40Km/h RPM 2858, Dilution 14.2, valid @ Idle, RPM 751, Dilution 12.6, valid Analyzer Software Version: 3.53 -------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------- Results: 2004 HC ppm @ 40Km/h ASM 2525, 33, limit 86, pass; @ Idle, 196, limit 200, pass CO % @ 40Km/h ASM 2525, 0.02, limit 0.48, pass; @ Idle, 0.33, limit 1, pass NO ppm @ 40Km/h ASM 2525, 301, limit 663, pass; @ Idle, -, limit -, - (not done) @ 40Km/h RPM 1982, Dilution 14.9, valid @ Idle, RPM 760, Dilution 13.20, valid Analyzer Software Version: 3.16 --------------------------------------------------------------------------------------------------------
Roger, I have a few questions and a comment: Is the Service Engine Light lit? (You do not say...) Why do you think "the EGR valve is fine?" How many total miles on the engine/vehicle? How many miles in the 4+ years since the old EGR was replaced? When you replaced the EGR valve, did you also thoroughly clean the intake manifold port? Based on the symptoms you describe, I'd personally suspect the EGR is not operating correctly (if I recall correctly, the '95 was still vacuum operated so look at the rubber hose and diaphragm for small cracks) or the EGR passage in the manifold is partially blocked. By the way, 4 years and 50K miles is about all you get from the EGR, especially if the engine burns a good deal of oil. Good luck. Bob
Hi Bob Thanks for your reply. No service light is not on. The original EGR valve gave me trouble back in 2004, not before then, and lasted for about 9 years. What happened then was my car was stalling when dropping the RPM on the engine, example decelerating and coming to a stop. I had removed that EGR valve and cleaned it with carb cleaner... the benefit lasted a couple of weeks then it began to stall again. I replaced the EGR in Oct 2004 and have not had the same trouble since then. Total mileage of my Saturn: 228,800 Km / 142,000 mil. (mostly highway) Total mileage of my Saturn since the old EGR was replaced: 81,700 Km / 50,700 mil. (done @ 147,000 Km). I cleaned the base where the EGR valve mounts, the breather hose or crankcase vent hose, the throttle bore and plate, the hose to the PCV valve and replaced the PCV valve. I did not take apart the intake manifold. Do you mean to get at the gasket too? As I understand it, that is a big job..... here is a link to a doc as I understand that you mean by accessing this port. Am I right? http://wiki.rockauto.com/2000 SATURN SL SERIES 1.9L 116cid L4 FI (8)_Intake Manifold Gasket_0_0 The vacuum hoses and PCV grommet are in good shape. Yes, this car does seem to burn alot of oil.... 1L every 2000 Km or so. I'll remove the EGR valve to examine it this weekend and clean it w/ carb cleaner.... but it seems to be operating well at present. Thanks, Roger
You've got to stop using Nitro while you are running it at the Funny Car Circuit Sorry I can't offer any real help. I just went out to check the emissions inspection reports on my 97 SL2, but for at least the last 4 years, they have not listed actual readings (here in CT), only pass/fail. Good luck with yours. JimR
Are you referring to a vacuum type EGR? Mine is 17 years old with 330k miles on it and still gives me good emission tests (except for the last one, it was a close pass - it might fail the next one in a couple of months) Alex
Hi Bob I removed my EGR valve on the weekend. There was a fair amount of carbon in it, however the valve spring was not sticking. I did clean out the valve holes and spring the best I could with carb cleaner/solvent. The car still runs ok. I'm going to replace the 20 month old RC12YC Champion spark plugs that are currently in the engine with RC14YC's, a spark plug with a higher heat range. I'm not sure if the problem is with the catalytic converter...... exhaust is flowing, no plugs in the pipe, and CO and HC test results were always good. Maybe I should do another retest first, see if cleaning the EGR valve, changing the spark plugs, and using 91 octane gas works? Thanks, Roger
Roger, It might be worth re-checking the NO emissions before you do any more work. The blocked passages could have been the root issue here. When you had the EGR out, did you also verify that the vacuum control was working properly (since failure in the diaphragm and/or the vacuum hose are common for that vintage)? On the higher heat range plugs, I personally do not believe those are your problem. I would make sure they are clean and gapped properly though since the carbon you saw in the manifold from the oil consumption is likely also on those plugs too. On the high octane fuel, in my opinion this will not do anything to help you since that year Saturn did not use computer advanced timing to allow you to get any advantage from the higher octane. (If anything, it might even cause the vehicle to run worse. At best, all you are doing is paying more for the fuel.) Good luck and let us know what you find is the problem. Bob
Thanks Bob I did not check the vacuum control. How does one do that? I'll research this... http://www.asashop.org/autoinc/dec97/egr.htm Cheers, Roger
I hope this helps: I have a SL1, 1997, SOHC, 171000 KM. I ONLY use Synthetic oil Mobil 5W30 (good deal @ Costco), changed every 5000 Km. I ONLY use the K&N oil filter. I prefer to invest in preventive maintenance. Every couple of years (here in Toronto, Canada), I must have it emission test certified for at time of license renewal, which is the date of my birthday (February! Bloody Winter cool!). The tric I use (again, just my situation, which might apply to you or not), is to have the engine VERY hot before going to testsite, and change the PCV valve (regardless how good it mght look from outside), a couple of hours before. Also, I fill the tank with the highest octane gasoilne. Regulations here require the testing of leakage from the gas tank cup. I have another cup (brand new), which I ONLY use at test time, to swap few hours before the test. Somehow (yes; folks; I'm knocking wood), seems to have helped. Good luck.
