 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Driving, Maintenance, Tuning / General Car Topics / August 2006smog check HC question
Hello. I replaced cat converter 2 yrs ago to bring down HC in wife's 81 VW Scirocco. Now the car's failing due to high HC again. Results: 15mph, 1807rpm HC max: 162 - HC meas: 149 CO max: 1.09 - CO meas: 0.27 NO max: 1227 - NO meas: 983 25mph, 1938rpm HC max: 132 - HC meas: 172 FAIL CO max: 1.09 - CO meas: 0.27 NO max: 1227 - NO meas: 791 The car is used exclusively for short trips except was driven about 15-20 miles on the freeway before the test. It has over 250K miles, and uses about 1qt oil every month (not sure how many miles, no exhaust smoke in normal driving though). Question: I put a bottle of Techron in the tank. Is there a chance running that out on the freeway would clean up the test results, or is a new cat the answer? Also: what effect does Techron have on a smog test? Does it all have to be run out and refueled before testing? BTW, it's an aftermarket cat, considerably less $ than OEM. thx, nf > Hello. > [quoted text clipped - 27 lines] > thx, > nf Question. Have you considered having a compression check done on the engine? If the mileage is as high as you stated, compression might be quite low and the blowby of oil mist (through the pistion rings where they mate with the cylinders) from the bottom half of the engine to the combustion area at dead top center might be quite excessive. Now that would indeed increase your HC. You have an old engine and even the valve stem seals and hydraulic lifters could also be causing problems. How does it run? Is it a smooth running engine with plenty of power or not? There are many things you must consider. A refurbished engine is what I would be leaning towards after checking the Cat Converter for blockage and corrosion and rebuilding the carburator. If you are mechanically inclined checking the compression is something that you could easily do yourself. Checking the blow by is something best left to the garage as they have the setup with compressed air required to test the engine health. Swapping out an engine in a Scirocco is not difficult, especially if yours is an 8 valve engine.I presume your 81 Scirocco is an 8 valve engine. 16 valve engines were from 1986 on in the US versions. A decent mechanic can swap out your engine in 3 hours including mounting the gearbox you have with the refurbished engine. I love VW's. I have owned a Super Beetle, 2 Sciroccos, A VW pickup with a 2.0 liter 16 valve engine and currently own a Passat with a 1.9 TDI engine. Good luck!! > Question. Have you considered having a compression check done on the > engine? If the mileage is as high as you stated, compression might be [quoted text clipped - 8 lines] > after checking the Cat Converter for blockage and corrosion and > rebuilding the carburator. Thanks for the reply. Car's currently running smooth with good power. It's an FI engine, no carb. My mechanic never did a compression check and I don't have a compression tester. Plugs don't foul and smoke is only visible when accelerating. The first time it needed a new CAT to pass smog was in 98, then again in 04. And now, only about 2.8K miles later, it seems to need one again. My mechanic suggested running a tank with Techron, because the most typical trip for this car is less than 3 miles (about 1200mi/yr). I've got to get past the smog check and can't afford big $ now. Basically, I'm looking for feedback as to whether there's any hope a long drive with Techron could get the CAT working again or otherwise lower HC, and how Techron mix still in the tank will affect a smog check. And any other suggestions how to get under-load HC from 172ppm to under 132. nf > Thanks for the reply. > [quoted text clipped - 15 lines] > > nf Since your car has been driven for only short trips, carbon will accumulate on the heads of the pistons and around the valve faces on the cylinder head. What I used was the extra strength chevron additive with techroline and a long drive (@200 miles round trip) with bursts of high speed. My 1992 Corrado SLC had been sitting in my folks driveway for almost 1 year (I live overseas in the Netherlands) and not driven. I was quite worried about the old premium gas in the tank. My Corrado's VR6 engine perfomed flawlessly and it passed the Georgia smog check easily. Occasional long drives are needed to keep your fuel system and intake/exhaust system healthy. I would expect that your spark plugs have some carbon buildup as well. Try changing out your spark plugs and air filter before the drive and oil w/ oil filter change before you go in for your smog check. There are some additives sold in parts stores that state that they guarantee a pass on the smog check. Do a little research onlilne before you buy as the small bottle of additive is not inexpensive. If I remember correctly,your car ( my second rocco was an 85 model) has an O2 sensor located in the header downpipe of the exhaust system that might need to be changed.Just look for the wire that goes down to the exhaust from the engine. There is a description of a resistance test (with a multimeter) to verify the sensor's operation, in the VW shop manual for the scirocco. Normally if your O2 sensor fails, the mileage will drop down, the engine will run rich and the car won't run as smoothly as normal. By the way, there should be zero visible smoke under acceleration for a healthy fuel injected engine. If the smoke is colored blue you have bad rings( read engine rebuild time) and if it is colored white you have a fuel injection (easier to solve) problem. The seals for the injectors become brittle with age and heat. Faulty injector seals will cause problems with the mixture delivered to the affected cylinder. It is easy to break the seals, so unless you know what you are doing, leave the job to your mechanic. I have no idea what your mechanical skills or level of gasoline engine knowlege is. I hope that I have not overdone the amount of information that I have given you. Is your mechanic a VW guy or not? If he is or is an ASE certified mechanic, he should be easily able to diagnose the problem. Did you tell him about the smoke under acceleration? I hope for your $$$ sake that the smoke is not blue. > > Thanks for the reply. > > [quoted text clipped - 55 lines] > tell him about the smoke under acceleration? I hope for your $$$ sake > that the smoke is not blue. I just looked through my library and found my Bentley Scirocco book. It covers 1985-1993. The correct smoke colors to look for are Blue-gray (cylinder head and piston or piston ring problems) / Blue-gray and or white steam in exhaust (cylinder head gasket failed, Warped or cracked cylinder head or cracked cylinder block) / Black smoke - (Rich air/fuel mixture). > Since your car has been driven for only short trips, carbon will > accumulate on the heads of the pistons and around the valve faces on > the cylinder head. What I used was the extra strength chevron additive > with techroline and a long drive (@200 miles round trip) with bursts of I added a bottle of Techroline to about 9gal gas in the tank. Today I went for a 200 mile drive. Ambient temp 90-100F. From about 500ft to >4000ft above sea level with one very steep grade. The first 100 miles was kept in 4th gear, with speeds 60-75mph. Return trip (mostly downhill) a mix of 4th and 5th, speeds 65-80mph. Uphill oil temp read as high as 160F. Downhill 120-125F. Water temp well within normal. Occasionally floored accelerator to above 80mph. Driver side window was open. Fuel mileage was almost 32 mpg. Oil consumption was a bit more than 1 pint (freshly changed with - as always - Castrol 20W-50). There is a noticeable difference. A slight preignition rattle between 2500-3000rpm is gone. The engine is running better than it has in years. I checked plugs (2800 miles on them) and they did not look heavily carboned. Will check again to see if any noticeable change. I've replaced an O2 sensor previously to pass smog. IIRC a faulty O2 sensor produces a rich mixture with high CO readings as well as HC. My CO reading is low, but no harm in checking voltage. There is currently no visible smoke coming out of the exhaust in normal driving. (I had previously seen what I think was a mix of carbon and oil smoke when my wife drove away when engine was cold.) Now I must decide...take a chance and do free re-test, then pay for CAT and another test if fail, or go ahead and install new CAT which will almost certainly pass test. I'm tending to first option, as that will tell me if the drive with Techroline really did reduce HC. > you. Is your mechanic a VW guy or not? If he is or is an ASE certified > mechanic, he should be easily able to diagnose the problem. He's a VW mechanic but I haven't given him the car to work on this time (though he insisted on checking distributor vacuum advance/retard to make sure both were working after I flunked smog check). He suggested Techroline and a long drive. nf > I added a bottle of Techroline Oops, that's not correct. What I added was Techron Concentrate Plus, which replaced Techroline. For a feedback controlled, fuel injected engine to fail a smog check with high HC, you almost certainly have a bad catalytic converter. Since you seem to be killing them regularly, I am guessing you have other problems. When was the last time you had your O2 sensor replaced? My '81 Audi called for routine O2 sensor replacement (every 50,000 miles). On the other hand, the fact that you don't see any smoke during normal driving despite using over a quart per 1000 miles (250,000 miles in 25 years = 833 miles/month on average, and I betting you use it less these days) indicates that maybe the catalytic converter is working. I would suggest replacing the O2 sensor, doing an oil change, driving the car for at least 50 miles before the test to make sure it is completely warmed up (hot even), and adding a a can of one of the emmission test additives (see list below). http://passsmog.com/ http://how-to-pass-smog-test.rxp.com/master.htm http://www.midwayautosupply.com/detailedproductdescription.asp?21168 http://www.midwayautosupply.com/detailedproductdescription.asp?3026 http://www.smogtips.com/six_things.cfm http://www.protecusa.com/tbpuragas_emissions_test.htm There are lots more of these sort of "no-fail" additives at the local Pep Boys. They might help. Pick one with a gaurantee and you can always get a refund if it fails again. Ed > Hello. > [quoted text clipped - 27 lines] > thx, > nf Thanks for the reply, Ed. > For a feedback controlled, fuel injected engine to fail a smog check with > high HC, you almost certainly have a bad catalytic converter. Since you seem > to be killing them regularly, I am guessing you have other problems. When > was the last time you had your O2 sensor replaced? I believe it was 6000 miles ago. > fact that you don't see any smoke during normal driving despite using over a > quart per 1000 miles (250,000 miles in 25 years = 833 miles/month on > average, and I betting you use it less these days) indicates that maybe the > catalytic converter is working. Yes, smoke seems to have disappeared, and yet... so did 1 pint of oil in a 200 mile drive (see my reply to AviationTech). As for monthly miles, car had 210K in 1992 = 253 miles/month avg since. But for the past 5 years it's been more like 115 miles/month, most commonly for 4-8 mile round trips. > doing an oil change, driving the car for at least 50 miles before the test > to make sure it is completely warmed up (hot even), and adding a a can of [quoted text clipped - 9 lines] > There are lots more of these sort of "no-fail" additives at the local Pep > Boys. Not here in California. I think there must be a law against making that claim, as the auto parts stores here only carry gas additives like Techroline that claim to clean the engine. But I am definitely going to take your 50-mile ride advice. nf |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.