HC a little higher, and NOx too! '81 Scirocco

1st test @ 91.4F ambient temp. Started car. Drove approx 3 miles to smog tester.

15/25 mph, 1891/2055 rpm HC (PPM): 191/151 FAIL CO (%): 0.29/0.36 NO (PPM): 499/309

2nd test @ 68F ambient temp. Oil had been changed to Mobil 1 'high mileage', new plugs installed, FI cleaner added to tank, 3/4 tank burned at highway speeds, then tank filled with premium. Drove ~25 miles. Water temp mid point, oil temp @ 110-120C. Smog re-test: FAILED!

15/25 mph, 1893/1985 rpm HC (PPM): 210/195 FAIL CO (%): 0.34/0.19 NO (PPM): 2190/1541 FAIL

WTF?! The engine is running better since oil change/new plugs/FI cleaner. Rough start has gone - I assume the FI cleaner did something. Assuming the tank was actually filled at both gas-ups, the car was getting ~30mpg highway in 4th gear - 3K-3.5K rpm.

nf AKA "YADA" (Yet Another DAve)

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Reply to
nutso fasst
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Its actually not uncommon for vehicles to do worse on emission tests after new plugs have been installed. Not to mention you shouldn't add premium fuel unless the car requires it. I have actually seen cars fail because of this. Must be something to do with the extra additives in the fuel that aren't requried in the low compression engines.

If I remember correctly US 1981 Sciroccos came with catalytic convertors where CAN ones did not. Are you sure your cat & O2 sensor is working properly???

Reply to
Craig

New plugs cause that much increase in NOx? In 1998 new plugs plus CAT pushed HC and NOx way down. The plugs are the W7DC I just replaced with WR7DC+.

The tank had 89 octane in the tank for the first test, but it was pinging on acceleration. It is designed to run on 91 octane, would 3/4 tank 93 octane pump NOx up?

I thought faulty O2 sensors resulted in a reduction in gas mileage and a rough running engine. After current maintenance, the engine ran smoother that it did when it passed the test 2 yrs/3300 miles ago. Perhaps i should put a voltmeter to it anyway and see what it reads.

I have no way to test the (aftermarket) CAT. I installed it 4 yrs/10K miles ago, maybe it just used up its catalysts.

Interesting to compare Scirocco to a 2001 2.3L DOHC Ford Ranger that also gets driven very little. Last smog check on Ranger: HC: 0/0, CO: 0/0, NO: 2/4

thanks, nf

Reply to
nutso fasst

YADA.............I like it! lol

Did you install new GOOD spark plug wires, cap and rotor also? You have to get the ign system working very well, so checking the ign. coil is usually a good idea too. Which spark plugs did you install? Bosch W7DC? I have had very good success with Bosch Caps and rotors, but limited success with Bosch spark plug wires with the Rabbits. Strange that I have found 2-3 bad new sets!!!

Observations and ramblings......................... Usually retarding the ign. timing a little will reduce the HC some or increasing the CO will also usually reduce the HC some. So what is the ign. timing set at and does the vacuum advance work on this distributor? Does it only have 1 vacuum hose to the distributor? I have seen the mechanical advance stick in some distributors too!

Important.........What did you set the freq valve to on the dwell meter? What is the max CO that your engine can emit? Also increasing the CO some might reduce the NOx too.

CO did not go down during the 25mph stage of the first test. That is interesting if the 02 sensor system is working!

HCs and NOx went up in the second test but at least the CO went down in the

25mph stage of the second test. NOx can be created by a hot exhaust and some vehicles had an EGR system. I forgot if your '81 has one, but I think not.

There could be vacuum leaks around the engine and especially at the fuel injector seals. Spray some carb cleaner at the FI seals and note the engine rpms.

some light reading............

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Reply to
dave AKA vwdoc1

PINGING? UH OH! It could indicate that the ign. timing is way too advanced. Or the cylinders are starving for gas, i.e. fuel pressure too low, fuel delivery through injectors too weak, deposits sucking up fuel before it enters cylinders, etc. Or combustion chambers getting too hot. Compression too high. Or vacuum leak is possible. Or bad gas. OR..............???

I have always informed people to stay away from that midgrade gas. It has caused running problems with several different engines where the problem was solved simply by dropping to regular gas. Talk about a "cheap" solution!

I won't get into any debate about the midgrade gas is just some premium and regular gas mixed at the pump. Just mix it yourself if you want a blend! 8^)

Testing the cat can be done with a CO tester before and after the cat. I was also informed that it could be done easier with a NON-CONTACT INFRARED THERMOMETER before and after cat. Exhaust temps would be warmer after the cat, but not red hot! lol

Reply to
dave AKA vwdoc1

Hi I'm wondering if a 3 mile / 5 km drive is sufficient to warm the engine and exhaust system to full operating temp? Did you start out the 3 mile drive from a cold start? Do you drive at city speeds (30 mile/hr zones) to the testing station? Perhaps go for a bit longer drive to get the engine and cat up to operating temp. If you can get out for a short ride at highway speeds. If there is a good hill at hwy speeds, so much the better. Or go do the test after you've run around town doing errands, whatever you need to do to get everything up to temperature. Also when you get to the testing station do you leave the engine running while you are waiting in line to be tested (yes, do leave engine running). If the testing station tests the seal on your gas cap, unlock your gas cap beforehand at home rather than stop the engine at the testing station to unlock the cap for them (assuming you have the lock in the gas cap). Just some ideas.

-Tony '85 Golf with no cat, '90 Golf with cat (both Canadian models), pass emission tests annually

Reply to
tonyw

Like I said check the CAT. If the HC & NOX are high these are two things the cat should be cleaning up. Mostly the NOX. As far as the fuel goes before I turbocharged my 1981 Scirocco I never put anything other than 87octane fuel in it. I even emission tested it myself just for kicks & it passed with flying colors & in Canada ours didn't come with catalytic convtors.

Craig

Reply to
Craig

I have no way to test the (aftermarket) CAT. I installed it 4 yrs/10K miles ago, maybe it just used up its catalysts.

do you have one of them point and shoot non-contact guns?

Reply to
Lost In Space/Woodchuck

Most aftermarket CATS don't last much more than 1 year. They are extremelt cheap construction when compared to an OEM cat.

Craig

Reply to
Craig

The drive to the first check was not enough to fully warm the oil, and I turned off the motor for a few minutes. For the second check I took a 30 minute freeway drive and didn't turn off the motor, but the results - especially NOx - were worse.

nf

Reply to
nutso fasst

If the temp diff from intake to exhaust is 100F is the CAT still good?

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But this says nothing about a CAT reducing NOx, only CO and HC.

nf

Reply to
nutso fasst

Nope. 3 ATDC. I think 0 is spec. No ping with 91 octane gas. It is a bit odd that it's pinging with that much retard though, eh?

By golly, that sounds reasonable! :-)

May be time to buy a tester and find out how low it is. And go through the Clymer manual and check other things such as the ones you mention. I was lazily hoping for some 'silver bullet' where somebody replies: "Why, yes, the very same thing happened to me and I fixed it by..." But then, maybe with 255Kmiles I'm beating a dead horse as far as emissions go.

Thanks, nf

Reply to
nutso fasst

I think you measure just before the cat and just after the cat.

AFAIK NOx is created by too much heat.

Reply to
dave AKA vwdoc1

Some have used this trick to reduce buildup in the engine intake/exhaust/combustion areas. I am too afraid to try it on any engine but if I bought a engine with running problems, I would try it before rebuilding engine. For a fast clean up................... Add SEA-FOAM slowly in the intake, then towards the last of the Sea-Foam let it go in fast enough to kill the engine, and let it sit overnight. When you start it again expect some smoke, possibly a lot of it. Some have used Water or Automatic Transmission fluid to clean up the combustion chambers.

Do you have an EGR system on that '81?

Reply to
dave AKA vwdoc1

...

I've heard of this and similar. I'll look at other possibilities first.

Well, the Clymer manual implies so, but only diagrams '75 and '76 so I'm not sure. This Clymer has the '81 as sort of an addendum. Will check tomorrow.

BTW, how did the C to F switching go?

nf

Reply to
nutso fasst

Have not seen that '01 Golf to try the C to F procedure yet. Soon though! ;-) thank

Reply to
One out of many Daves

I would think the temp difference should be greater. Been awhile since I had to check a cat but HC is mainly controlled by the cat. And since your CO% in good, that leaves only the cat. Have heard if you dump about 4 or so bottles of dry gas the alcohol really cleans up the emission during a test. But then again with enough alcohol you then have a vapor lock concern until the alcohol is all gone.

Reply to
Lost In Space/Woodchuck

Smog test numbers were good even though CAT was over 210K miles old when typical trip was over 25mi. When driving dropped to 2-10mi per trip, smog numbers started to go up.

I'll attempt some diagnostics as soon as my ol lady doesn't need the car.

thanks, nf

Reply to
nutso fasst

I missed all the 101 stuff. I removed the cpr and attached the fuel pressure gauge. Cold and running pressure is correct. I removed the injectors and checked for proper flow rate and pattern. I removed the catalytic converter and inspected both the intake and outake of the converter for damage. As Dave mentioned Seafoam to clean the filthy intake valves and pistons might reduce the pinging. It is possible that the system is trying to get the car to run rich enough but an injector or two are not flowing properly so that is making the task challenging. Tossing the injectors in an ultrasonic cleaner for a half hour might help. I swear it did for my Toyota injectors but it could have been a placebo affect as I had to rationalize the purchase of the cleaner.

I know you were looking for magic bullet but you might be at the 101 troubleshooting that the Bentley manual covers in great detail. Low mileage driving is hard on the converter. I have a 21 year old truck with 275,000 miles on it. Original converter that appears to bee good with a visual inspection. County does not require emission testing. I used to drive it a lot but not so much the last 15 years. Trip to town is 7 miles so at least the engine get hot going to and from as all trips are done as a loop. No drive a few miles, sit all day and drive back home. The exhaust does not stink like a car that is supposed to have a converter but the converter was removed.

Reply to
Jim Behning

Thanks. I've decided to give the car to the VW mechanic who got it passed 2 years ago. I don't have the testing tools and can't afford hit-and-miss attempts to pass it. On the one hand I wish I'd done this initially, but in that case the plugs and oil change would still have been good prelim. Car is starting and running much better.

nf

Reply to
nutso fasst

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