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

nutso fasst wrote:
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!!

"AviationTech" <ecarter (AT) planet (DOT) nl> wrote

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

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/deta...tion.asp?21168
http://www.midwayautosupply.com/deta...ption.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

"nutso fasst" <no.replies (AT) no (DOT) where> wrote

"AviationTech" <ecarter (AT) planet (DOT) nl> wrote

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.

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

"C. E. White" <cewhite3 (AT) removemindspring (DOT) com> wrote


Thanks for the reply, Ed.

I believe it was 6000 miles ago.

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.

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

"nutso fasst" <no.replies (AT) no (DOT) where> wrote

Oops, that's not correct. What I added was Techron Concentrate Plus, which
replaced Techroline.