zellamsee

I have a 1996 993 Coupe with approximately 40,000 miles on the clock. I have owned the car for 17 years now. I live in California, and as a result, my car needs to pass a smog test every two years. Recently, it failed on account of the hydro-carbon reading being too high (not by much, though). The car was hot/warm during the test.

I understand that it is almost impossible for one of these OBD-II cars to fail an emissions test without having fault codes in memory. I will have my dealer double check for fault codes to confirm that there are none. The Check Engine Light is not on and it does light up when I first turn the key, then goes out when the car starts. The car runs strong, smooth and doesn't smell. It consumes very little oil.

I replaced the plugs and the dual ignition distributor about four years ago. Also about four years ago I did a pressure test just to check the health of the engine -- all cylinders were about 4%, except cylinder #4 which measured at 10%. I cannot imagine that I have a burnt valve and no check engine light. The OBD-II system is super picky . . . . But, perhaps a valve is the culprit here? An oil change was done less than a year ago.

I am attaching an image from the smog "fail" report.

Any insights as to what to do here much appreciated!

Attachment 953064

Quadcammer

get the car screaming hot. I mean run it HARD and schedule your appointment so that you can get in immediately. That should solve your problem.

Steve Weiner-Rennsport Systems

Good advice from Quadcammer. I would also follow those words up by a long drive (to get it hot) with a good fuel additive in the tank.

I've had excellent results with these issues since 1985 using a cocktail of LubroMoly Jectron and Ventil Sauber together. These products do a good job of cleaning injectors and the soft carbon buildups on the back of the intake valves. One can of each product into a near empty tank, fill it up and go for that hard drive.

bruce7

Agree with getting the car hot before testing and occasional use of gasoline
additives mentioned.

Here is my test results from last fall. HC is quite a bit lower than you tested. And
this is before I replaced plugs, wires, caps/rotors, valve lifters and cleaned the
fuel injectors.

I would check for vacuum leaks which are common on this engine.

Also, here is some technical information related to the gas readings you might find
interesting: http://www.ratwell.com/mirror/interro/techgas.html

Dan V

Others have had success with alcohol:

https://rennlist.com/forums/993-foru...l#post10306874

I did same as Ted with my '97 w/114K mi back in Jan, and although I probably would have passed without it, I can confirm that it doesn't do any harm.

Steve Weiner-Rennsport Systems

I would never use any additional alcohol in the fuel unless I was trying to rid the system of excess water. There are FAR better additives to use for other purposes and you really don't want to deal with any untended consequences.

stuttgart1

http://www.amazon.com/gp/aw/d/B000CIPUR8?vs=1

Give this a try, I always pour a bottle before i go amog. You can get them at Walmart, Autozone, O'Reilly.

zellamsee

Thanks for all of the replies.

Shtootgart

Says "not VOC compliant in CA" , did they ship it to you in California ?

goldcountryboy

The last time I passed I had the technicians do a pre check. They hook it up to the machine and run the idle up until it's smoking hot. I passed with flying colors after I had failed pryer.
It's a good idea to change your oil right before the test also.

nine9six

I concur with getting a things good and hot via a long drive, with a full tank of gas and additives as Steve W suggests; but I'm at a loss, as well as curious as to why this is a good idea?

If anything, I'd change the oil AFTER running the tank of fuel with the additives; but that's just me...

OverBoosted28

Just register it in a non-smog county and be done with these worthless, smog reducing programs that have absolutely no effect on harmful emissions. Our cars are not driven enough to even make a dent in what the millions (if not billions) of gross polluters out there that squeak through the cracks of the fine CA DMV and CARB systems.

Shtootgart

I like the idea of having older cars get a pass. Of course, that won't happen because these tests are big money makers for the DMV

doublecabmel

Ca is absolutely the worst for this stuff. Even though the car blows low levels of emissions, they always get you for something else- for me it's the stupid rediness codes. All of my cars that are obd2 (993, 430 Ferrari, 360 Ferrari, etc) all fail miserably. It's so annoying. Wholesale dealer plates are probably the best way to go.

goldcountryboy

I copied this from a car forum
It most certainly can give you better results..... Have you ever heard of blow-by??? Open up your oil filler cap when the engine is running. Feel the air coming from the crank case??? That is exhaust, or blow-by. If your exhaust can enter the crank case with the engine oil, then the engine oil can be contaminated with unburned fuel. This blow by gets sucked right back into the engine by way of PCV valve. Have you ever changed your oil and felt like the engine is running 100% better???? Think about it.