weird smog check/please help

jerrykrug · 10-20-2003, 11:41 AM

I did a "pretest" the other day on my car and wanted some advise. Passed all the underhood inspection even w/ SSI's so I am pleased about that, but the #'s from the test seem odd.

2500 RPM (ACTUALLY 2384 RPM)
HC/PPM (ALLOW) 0480 MEASURED 0072
CO% (ALLOW) 1.70 MEASURED 4.20% FAILED
CO2 MEASURED = 8.2
02 MEASURED = 6.1

IDLE (749 RPM)
HC/PPM (ALLOW) 0220 MEASURED 0880 FAILED
CO% (ALLOW) 1.70 MEASURED 0.66%
CO2 MEASURED = 7.7
02 MEASURED = 9.0

Is it normal for the HC/PPM to be high @ idle and low @2500 rpm?

Is it normal for the CO% to be low @ idle and high @2500 rpm?

I leaned the car out so it just started to stumble, does anyone know if this is symptoms of vacuum leak, bad ignition, valve problem etc...

PS: the car is an 1980 911sc stock except for the SSI's and has about 1000 miles on 18 month old oil.

Thans in advance

juanbenae · juanbenae's Garage

do you have a cat and oxygen sensor? normally the SSI will not allow for either and this could be leading to the high numbers.

jerrykrug · 10-20-2003, 11:55 AM

No cat but I plugged in the o2 sensor for the test, 1st time its been plugged in in over 2 years, car has 163K miles & runs good overall

jerrykrug · 10-21-2003, 06:39 AM

bump....Anyone?....I am really trying to figure out if I need to put my old (stock) exhaust on (PITA) or if I have other issues like vacuum leak, injectors etc....

Thanks

Joe Bob · Joe Bob's Garage

Well, the best that can be done is to put it on an exhaust analyzer and then lean it out via the adjustment under the air box.

If it still fails it needs some diganostics. At least in your area you do not have to do the roller.

When was the last time the valves were adjusted? Are you sure you don't have an intake or other vacuum leak?

juanbenae · juanbenae's Garage

if there is no cat it is nearly impossible to pass the calif emissions testing. i have a 78 and have resisted the SSI's for that very reason. even every two years for an exhaust swap out is too much.

can you "move" to nevada and register your car there?

HarryD · 10-21-2003, 07:02 AM

Check this POST . There may be something there to help you.

Seems to be a different verse of the same song.

Boy am I glad I live in Orygun with a DEQ exempt vehicle!!

makaio · 10-21-2003, 07:11 AM

When I smogged my SC last January, there was no way it was going to pass without the cat. The numbers were just too high. Fortunatley, I have a spare that came with my CAB, since the cat on my SC had been gutted for some time.

dvkk · 10-21-2003, 12:38 PM

The first thing I noticed is you have an oxygen dilution problem. How well was the probe installed in the muffler? If it only went up a short distance, you'll get this problem. It can be caused by exhaust leaks as well. The reason you need to address this is that it artificially lowers the HC and CO. Depending on how the test was done, some jurisdictions actually multiply your CO and HC by a fudge factor to compensate. I don't trust this, so I try to minimize the O2. Try to get the O2 down to 2% or better before you try to adjust your engine. With the O2 below 2%, the CO and HC readings you get will be accurate. You will also note that the sum of O2 and CO2 will always be around 15-16%

What is your timing set to? If its advanced more than stock, this will cause hi HC at idle. Retard it to spec.
What is factory recommended idle speed? If you are at the bottom of the range, increase it to the top, or go over a little bit. This will help HCs too.

jerrykrug · 10-21-2003, 03:59 PM

Thanks for the great replies. I will need to adj. my timing back to factory spec, forgot to do that before the pretest. Would a vacuum leak be the culprit of the high o2 #'s and if so should all the other #'s come close to spec if the leak is fixed? also I would think that with the co% at .66% at idle it should be pretty close to passing at 2500 rpm?

Thanks again, any other imput would be great

Silveresrty911S · Silveresrty911S's Garage

Don't you guys in Truckee get a fairer shake when it comes to smog tests? My brother lives in Truckee and my parents have a cabin in Soda Springs and my Dad was talking about registering his SUV in Nevada County because of the easier smog regs up there. Wasss Upppp!

Rick

makaio · 10-21-2003, 04:41 PM

I think it's easier, in the fact that they don't have to go on a rolling road, like you probably do down in So-Cal..

Joe Bob · Joe Bob's Garage

Quote:

Originally posted by k911sc
if there is no cat it is nearly impossible to pass the calif emissions testing. i have a 78 and have resisted the SSI's for that very reason. even every two years for an exhaust swap out is too much.

can you "move" to nevada and register your car there?

When I still had the 3.0 I passed w/o a cat, SSIs and dual out exhaust....but I did have a euro motor that was federalized with an add on smog pump.

jerrykrug · 10-22-2003, 07:38 AM

Truckee, is the same as other counties that have no rolling tests. Placer county (tahoe city) I believe has no smog requirements.

What part of the #'s game does the cat take care of? or does it lower ALL the #'s

any more thought on this
Would a vacuum leak be the culprit of the high o2 #'s and if so should all the other #'s come close to spec if the leak is fixed? also I would think that with the co% at .66% at idle it should be pretty close to passing at 2500 rpm?