Hi everyone, I have a question for the tuner guys.

Here is the background of my car. Purchased in Nebraska in 2002 and moved to California in 2004. Car is a 1999 Coupe with 82K and is not my daily driver....sees about 3000 miles per year.

1. First CA smog in 2005, passed with flying colors (only mods at the time were B&B PRT's and VaraRam).
2. In late 2005, I had Kooks LT's installed and dyno tuned at A&A. (full mod list: Kooks LT's, VaraRam and B&B PRTs)
3. June 2007, passed CA smog with flying colors (see picture below).
4. June 2009, passed CA smog but showed high HC content.
5. Late 2010, Installed Oil Catch Can (Elite Engineering) and performed SeaFoam treatment.
6. June 2011 (yesterday), failed the CA sniffer test for HC content.

So, I have not changed the configuration of my car since late 2005, same tune and same mods. The last time I replaced the spark plugs was late 2004 and I plan to replace those this weekend to see if that helps. Also, I've noticed some pinging at certain RPM and I think I've been getting worse fuel mileage the past few years. Can all of these issues be related? I installed an oil catch can and did the SeaFoam treatment earlier this year as well, but it didn't help with the fuel mileage or pinging issues.

Any thoughts on where to proceed? All other parameters were within range, only the hydrocarbon content exceeded the limits. I have attached a graphic to show the smog data for the past three visits....mind you mods and tune were EXACTLY the same (minus the catch can, but that shouldn't make anything worse, right?) for all three smog tests.

Thanks guys!

 

in a word - cats -

 

I had high-flow cats installed with my Kooks LT's in 2005. You think they could be bad? The car runs smooth with no loss of power and no rattles or funky smells.

 

yes, many of the high flow cats work well for awhile, but not near as long as an OEM cat.

 

Let's assume that I would need to replace my cats. I haven't shopped around for exhaust for quite some time, are there any new products out there that are fairly cost effective and wouldn't alter the tune that I got back in '05 when I had the headers installed? I remember seeing Random Tech cats, but if I recall those can be very pricey.

 

Couple things--Obviously they are not worried about the "visual" inspecition--As long tubes are flat plain illegal--Also-Any replacement cat has to be on the "calif approved list" most hi-flows are NOT-so again they aren't concerned with that either--
Typically cats remove the NOX emiisions mostly--You have high HC amounts--
What causes your high HC #'s are your LT's----LT's have the 02 bungs further back than they were with the stock manifolds--So consequently you get erroneous 02 readings-- The fuel becomes way richer than the stoich of 14.68 and causes the high HC levels-- (somewhere around 14.0-14.3)The 02's don't heat up properly and read incorrectly---many people will install the rear 02's onto the front locations--The rears heat up better and are more sensitive--I have seen this work sometimes in aiding with smog testing.
Another thing to help the cats "light off" and heat up ( the cats don't get hot enough because your AFR is too rich) is to REMOVE some timing in the RPM areas and fuel use areas in your tune--So in your case from idle to about 1600 in th lower fuel use range ( approx
.15- .40 grams) I would REMOVE about 5* of timing--This absolutely will work--I do it all the time for customers---Then after it passes return your tune to the way it was---
Be sure to warm your engine up thorougly before you go--Get some good Chevron gas--

 

tblu92, thank you for the reply. From my 2007 smog check, the HC content was fairly low and I had the LT's installed for 2 years at that point. I understand time is a factor, but I'm trying to get an idea of what changes over time might effect the HC content. spark plugs, wires, O2 sensors.....

 

Were the cats hot prior to the emissions test? Hi-flow cats need to be hot to run efficiently. I put 15 miles on mine prior to testing and I passed with ease

 

Yeah, I drove the car to work that day (12 miles on the freeway) and to the smog station after work. On the way there I ran it at fairly high RPM to heat up the cats.

 

Some things to consider!

Clean your MAF! Use some MAF cleaner and SPRAY out all the dirt build up. Let it evaporate and reassemble.

Find someone with EFI Live or HP Tuners or someone who has an advanced scanner that can read live data. Data Log the engine.
EXAMINE the O2 sensor operation.. In Closed Loop steady state cruising and at idle, the O2 sensor output should swing LOW to HIGH, LOW to HIGH etc...... The swing should be somewhere in the 180-200 millivolts range (LOW) to 800-850 millivolt range (HIGH)

If the O2 are staying around a very narrow reading or stuck at 450Mv,, there bad or the circuit is compromised (bad sensor, bad connectors or wires.

Read the actual CATs with a infrared thermometer and see if there lighting off and working.

Look at your LONG TERM FUEL TRIMS. See where they are at. Ideal readings should be ZERO to very slightly negative. If there very HIGH, you have a leaky injector, bad O2 Sensors, VACUUM/AIR LEAK, etc..

Data Log and see what the engine is complaining about.



Bill

 

Thanks for the input Bill. I am going to replace my plugs and wires this weekend and give it another shot. I'm hoping the problem is not cat/02 sensor related, but the only way to be sure is to rule out other things first.....plus the car is in need of a tune up anyway. Also, I don't have any tuners or friends close to me that can read live engine data.

 

You could always purchase your own diagnostic scan tool. There are tons available

I have a ACTRON CP 9180 and it has live sensor data capability. $130

AMAZON.com

BC

 

That's a good idea. I didn't know they were that affordable. Could be fun too.

We have a 1 year old daughter now so my "Corvette Time" has been slashed to a minimal amount.

 

I replaced my spark plugs last night with stock AC-Delco Iridiums and the NGK's that I took out looked pretty good actually. My GM hot wires should be in today, so I will attempt the smog test again tomorrow. I have a sinking feeling that this will not solve the problem and the more I look into this, I'm leaning toward the header/02 sensor issue with installing long tube headers.

I have Kooks headers, which were installed by a shop...not myself....and then dyno tuned. Correct me if I'm wrong, but the Kooks headers incorporate all 4 02 sensors, correct? I'm wondering how the tuners deal with the 02 sensor tuning aspect with the Kooks headers. Do they turn off the rear sensors? I keep going back to my smog test in 2007, in which the setup was identical to now (headers were installed for 2 years) and the car produced low amounts of HC. So, the current setup is capable of passing I just have to find out what went bad. A faulty O2 sensor would throw a code and I have not had any codes over the past few years.

Any additional help is appreciated. I don't have a good reliable tuner near by to help either.

Thanks,

 

Have you cleaned your MAF!
Use some MAF cleaner and SPRAY out all the dirt build up. Let it evaporate and reassemble.

While your in there, clean the Throttle Blade and carefully examine your PCV system hoses for damage/rot. They get soft and rot from the oil and then you have a very large air leak. Chech the hoses and fittings from the manifold to the valve cover. Ive see too many with damage not to recommend that you check that.

Here is a picture of the PCV hose on my 02. Its different than yours. That U shaped hose rots and cracks a LOT on the 2001-2004 C5s:



BC

 

I recall cleaning my MAF sensor a few months ago when I performed the SeaFoam treatment. Either I cleaned it or I noticed it wasn't too dirty....but anyway, I will check on that tonight when I finish up the plug install. I will also check the PCV hoses. I will check in detail tonight, but my hoses tend to be in really good shape. Also, I looked through most of them when I installed the catch can a few months back too, and nothing jumped out at me.

 

Well,, If all that stuff checks out, the next step is to data log and see what the LTFTs are and look at the Primary O2 sensors and see if there cycling properly (high/low,, high/low...... If there dead and hanging out at one voltage (450 mv) thats your issue in a nut shell!

So,, When do you get that scanner?

Bill

 

Which scan tool do you recommend? It looks like Actron now has a CP9575, CP9580, CP9185 and CP9190. Which one is equivalent to the CP9180 that you have? There weren't any CP9180's for sale at amazon.

 

Dang, you've got some very lenient smog techs up there. I'd be dead in the water if I showed up for a smog test with LTs and a Vararam!

I always swap in a Z06 airbox setup. This year I replaced its air filter and scored a 5 PPM HC reading - way lower than when the car was brand new, ao it's still a puzzle to me. The difference I can think of is that I've been using Shell gas (with nitrogen) almost exclusively.

 

Did the smog shop give you any hassle about the LTs on the visual inspection? I'd hate to see you spend all sorts of $ to pass the sniffer and then have him send you back to swap the LTs for factory manifolds. I believe that a lot of guys here in CA actually swap headers for manifolds every other year during smog test and then swap back - you may get stuck with this route.

Also, don't rush down to the smog shop after you get things fixed from a hardware perspective. Remember that they still need to do the OBD tests and if your evap cycle or other electronic emissions tests haven't happened, you won't pass because of that.

Good luck