IROCtheZ28

Thought I'd pick your brains about my emission test failure. Here is the test results. As you can see I flunked 2 out of 3 parameters.


Just purchased this black Z28 Motor is an 88,000 mile L98 TPI 350. Last night 1 can of Seafoam was added to a full tank of 87 octane fuel. Today was a nice drive with no problems before the emissions test. I should have done a basic tune up prior to the test but the previous owner said it'll pass.

So I have the entire weekend to wrench on this temporary problem and perform the following basic maintenance parts swap:

Spark Plugs ( tell me which ones are L98 350 TPI decent? )
Cap
Rotor
Ignition Wires
PCV Valve
Coolant Flush
Thermostat ( 180* or stock 195*?)
Gatorback Poly V-Belt
Oil Change + Filter ( going Mobil 1 Synthetic VS Valvoline )
Fuel Filter
K&N Air Filters ( done )


I won't mess with the EGR valve yet but my O2 Sensors are in question and I'm not afraid to change them if it would definitely help me pass the next test. I just need your opinions about the Hydrocarbons PPM & CO% readings shown at the top of this post. I'll state that this is an original Dual Catted exhaust with a Flowmaster Cat-Back setup ( original GM catalytic converters ).

A deeper 'Search' in other L98 related websites mentioned using denatured alcohol to raise my chances to pass this test or mess with the timing. I can do the denatured alcohol bit but how much if any of you used this trick? I still have 3/4 of a tank of 87 plus Seafoam, should I expel all that and refill with 93 Super Unleaded?

Newbie Question #1: Would you Seafoam an 88K mile motor?

Newbie Question #2: When's a good time to replace the catalytic converters?


I'm being real here, the previous owner was a cop and didn't mention doing anything else besides an oil change and I did ask him about the rear and transmission fluids and he said "it's all original".
So with all that information, I have much to attack later.

cars3

Your car is designed to run on premium fuel. Yes it will run on regular 87 octane, but you should always use what the owners manual says. Three of my cars say premium and that's what they get. I can only get 91 octane near where I live.

IROCtheZ28

You're right. This from the '92 Service Manual.

cars3

That answers at least one of your questions. As far as emission testing goes I can't help. Never had to do that before Looks like a very well maintained car.

mako350Z28

Never had a problem with emissions testing, but it looks like you have all the basics covered.

Nice looking Camaro, btw.

Gord's Green Z28

Those are some stringent emissions standards you have to pass. Your car would pass TX emission standards. My car would fail CT standards even though it passes TX standards.

Limits allowed here are:
HC 148 ppm
CO% 0.83
NOx 1014 ppm

I'd say you pretty much have everything taken care of in your checklist of stuff. As far as 180 vs 195° thermostat, if your car is going to be running for awhile, it will probably be around 190° anyways. (Pick a hot day outside if possible. And take it for a LONG drive on the highway before you go to the test)

20 year old catalytic converters may be suspect. But then again, your numbers aren't that bad.

New O2 sensor is a good idea. If you have the special O2 sensor socket, it makes changing them a breeze.

IROCtheZ28

Update:

Failed my 2nd test after replacing all the mentioned parts above, even the O2 sensor. I put on at least 100 miles of break in cruising since this past Sunday. BUT I did manage to pass 2 out of 3 now, so I'm making some headway at least. Below is the emissions test from today.


I did not touch the EGR, Catalytic converters or mess with the timing yet. The timing part I need direction on as I dont have a timing gun, scanner or oscilloscope style diagnostic equipement on hand.

I also suspect the cats being 20 yrs old could be preventing me in a clean pass but any ideas would be helpful.

The fuel tank is full of Super V Power 93. Still it failed but not losing hope yet!

They put a fan on this time in front of the '92 Camaro.


Below is from the FIRST emissions test to show my intial test. What's next for me?

Marc 85Z28

NOx is where is should be, which means the cooling system and EGR systems are operating properly. Don't bother with the EGR.

Hydrocarbons are JUST BARELY passing, so don't assume they'll be OK next time around.

Now that you have the ignition system operating as it should (hopefully at least, replacing parts is only half of it ), you still need to get those unburnt fuel levels down. Check the fuel pressure, make sure it's within spec. Then I would run a can of injector cleaner. Not the kind you pour in the tank, but the kind that hooks up to the fuel rail - remove the fuel pump fuse and let the engine run solely on the injector cleaner. Then you could either retake the test and cross your fingers, or you may just need to replace those converters and be done with it.

Also, how does the engine run overall? No misfires? Any rotten egg smell from the exhaust?

IROCtheZ28

Engine runs smooth, purrs like a kitten and no rotten egg smell but I am deciding to order new cats. Wonder if I can get away with that without doing an adjustable fuel pressure gauge install or fuel rail flush?

Glad to see more technical advice given here. I will attempt to do whatever it take without blowing extra money away but the urge to upgrade this and that is very tempting. I have a long way to go.

I saw a video on the fuel rail flush, looks easy and solves injector woes?
http://www.youtube.com/watch?v=bKGI9N_yWd0

Marc 85Z28

Injectors get carbon deposits over time and this affects the spray pattern. Sometimes it can get bad enough to cause flow problems. Is it necessary? Only way to know for sure is to remove the injectors w/rail and apply a pressurized fuel source and power the injectors. The spray pattern will tell the story. But chances are with the age and miles, it's a good idea to perform it. It's cheap and relatively easy to do.

Adjustable pressure regulator? Not really necessary. Just make sure the system is within spec.

As far as the cats go, replacement will most likely get you to pass. On fuel injected engines I consider checking fuel pressure part of the tune-up procedure. I also recommend the cleaning of the injectors as I described not only for performance reasons, but clogged/leaking injectors can cause your new cats to fail too

Gord's Green Z28

Timing gun is $40. You absolutely need the special wrench that parts stores sell for adjusting the nut behind the distributor. Factor on $3 for that.

If you have a multimeter, try unplugging the wire clips from the fuel injectors and reading the ohms on the injectors. 16-17 ohms is good. 12 ohms is bad. Doing this when the engine is hot will have a better representation of performance.

I really wish they wouldn't put the fan in front of the car. That's helping keep it cool, which goes against helping you pass.

Cbystrack

have you sea foamed it through the vac system yet?? as a fellow CT person im deff willing to help. CT emissions suck! Where in ct are you?

IROCtheZ28

I put one can of Seafoam in the tank.

Poured at least a 1/2 of a can in through the rubber line at the brake booster very carefully.

Deep Creep'd the intake.

Changed plugs after that process along with a fresh fuel filter. It ran smoother actually but I'm still kinda stumped as to what cat system to install.

RockAuto had a smoothly bent dual cat w/pipes made by Bosal but it was 'unavailable' at checkout. Here's the pic that I wish I could order.


I reside near Tweed Airport.

68 RS/SS Ragtop

I had a problem with my O2 sensor even though they were brand new from auto zone. Changed it 2x, no go. Finally bought one from the dealer- no problems since. So I can vouch for Genuine GM on that part.

Love the POLO ll green, bummer to keep seeing pictures of it on the rack. Good luck.