Hi Folks,
I have a problem with 92 Z-28, it failed Maryland State Emissions test. The Hydrocarbons was 1.9262 GPM (S/B 1.2 GPM), the other reading were OK; CO=15.4372(Spec 20.). NOx = .7412 GPM (Spec 2.5). I restore the factory timing before I took the test. I am running a LT4 HOT Cam, 1.6 Roller Rocker, custom chip, 160 degree Thermostat , 2200 stall converter and 3.73 gears + other mods which I don't think changes the emissions. I still have ALL the emission devices - Dual cats.

I plan on the replacing Thermostat with a 195 degrees for the test only and running 87 gas. Does anybody have any ideas on how to get this car to pass the state test???
Bill

 

 

New Plugs, wires, air filter (K&N), and changed the oil 1 months ago (60 miles)

 

From what I hear you do want the 87 octance, but who really knows. Putting in the hotter thermostat and running hotter will definitely help.

Anyway, something that I found that helped was adding a couple cans of DryGas which can be purchased from Walmart for around a $1 each. It's basically alcohol and it directly effected my HC numbers on a couple back to back tests. I was trying to get CO down so it didn't really help me but the HC dropped noticeably.

Also, too high HC is often times running too rich, do you have an adjustable FPR? If so try dropping the fuel pressure. With your custom chip you may have a too rich condition which means you may have to try running the stock chip if you still have it. Assuming it will even run for crap with your car...

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Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

 

I learned that if you run rich, your CO -and- HC's are too high. Running rich= not enough fresh air, so you get more CO out of the motor. Whether that's true for all "rich" situations, I don't know.

Bill might be running lean, or have a missing cylinder. I wonder if the custom chip is affecting things... usually running "lean" gives more power, right?


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

Hydrocarbons are Unburnt Gasoline.


Simple as That.

CO is formed from a Rich Condition as well, combustion forms H2O from the HC and the O2.

combustion Forms H20 and CO and Co2 (and NO if the temp is High enough to allow the nitrogen to combine with the oxygen ). Now, if you are running rich such that there is not enough unspent oxygen after combustion, then You will not have enouhg O to go around to make all the existing CO's into CO2's, Soooo You get a higher CO number.

Whats the overlap On that Cam ? Overlap = higher HC as unburnt gasoline passes right through the whole Shebang w/o Combustion.

Overlap is what Kills Emissions.



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

Overlap on the LT4 Hot Cam is 112*, so that is most likely not the problem.........



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Matt

1987 GTA L98 MD8 GW6

"Stop Lights timed for 35Mph are also timed for 70Mph"

 

Run the engine at proper temp, higher temps cause other emmissions problems (i.e. NOX!!) Double check emmissions equipment that could have come loose (i.e. A.I.R. Lines) Make sure all ignition componants are good. Make sure EGR system is funtioning properly. I too failed emmissions 2 years ago in my 87. Turns out the EGR valve took a dump, and the @$$ hole at the station pulled the A.I.R lines off the smog pump. (Was too stupid to re-connect 'em! hehe)
Also, there is some crap at all auto stores "Gaurenteed to Pass emmissions" I never used it, but it says gauranteed!
Good luck beating the sniffer! I used to have to pass the California sniffer, now I live in Texas


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Corry Lazarowitz
clazarow@voicenet.com
clazarowitz@hotmail.com
1987 Pontiac Trans AM (GTA?) 350 or is it a 305?! TPI
SLP 1 3/4" headers, 3" cat back (stock cat
MSD ignition.
MSD Blaster SS coil.
3.73 Rear end gears
Accell 8.8 Wires
Bosh +4 Spark Plugs (Don't know if they really help but hell!)
Holley AFPR
Race Built Automatic trans ('vette servo, shift kit, tightly packed clutches)--just needs titanium gears now!
Newly gutted cat (the car gutted it's own cat!)
Hypertech Chip (Just found out I had it! :eek
More soon when funds are avail...

 

Hi folks,
About the LT4 HOT Cam, the spec for duration is 218/228 @.050, Center line is 112 and lift is .525 with 1.6 RR. I would have to believe the cam is the problem but I don't want to pull it. I will check the EGR value.
Bill

 

I used the Guaranteed to Pass... and I did- on the "new" NJ chassis dyno emissions test.

I also had my 8-month-old major tuneup, $6 "emissions test" K-mart air filter, 195 thermostat, removed the ADS chip and put the GM one back in, and cleaned up the inside of my distributor cap.

Then again, I don't have a cam or anything "special" like that...

------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

When i had my stock LG4 86 tested a few months back, it had levels about the same as what you got for your car. I put a gallon of NAPTHA (Coleman Camping fuel) fuel in the tank and past with flying colors. C0 levels dropped from 16ppm to .04ppm. HC levels dropped quite a bit as well, but i can't remember the excact numbers



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Current
86 TA 305 5 speed, hardtop
81 Z28 350, 4 speed, t-roof
99 Ducati 750 Super Sport

Former
85 Z28
94 TA

 

Denatured Alchohal. Dont use a lot it could hurt you injectors.

 

check for any codes u might have. mine threw an egr code after i failed emissions.

also, if u need more air goin into your exhaust, someone told me a while ago to replace the pulley on yer A.I.R pump with a smaller one. the smaller one will turn a bit faster sending more air into the exhaust. just a thought tho.

daniel

 

 

what you should do first is a compression check... make sure that verying thing is cool as far as that goes... next what is your base timing??? 8-10 degrees should do alright ( would effect NOX more than HC)... judging from the CO you shouldn't have a lean condition creating the hc problem (then again I am not familiar w/ how the test is run)... if all seams ok it could be the rocker ratio (1.6) that is putting you over the limit... another thing the egr is a control for NOX... unless it is crating a vacuum leak (lean condition) which is an outside possibility theeen I would lan away from it... do you hav any other nubrs like the o2 or co2 from the test??? those would be helpfull...

zroc (the chemist)

 

Im in MD too. High HC? Hmmm..

Was this the "sniffer test" or the IM 240 dyno roller test?

Did you gut your cat?

Try this....

1- raise the idle.
2- advance the timing a little.
3- hook your vacuum advance to a full vacuum port (manifold vacuum).
4- make sure its nice and hot. 180 t-stat should be ok.
5- drop the fuel pressure a little.

See if this helps

 

WTF are you talking about Zroc ? His lean condition creating the high HC ?


HC is caused by One or More of three things.


Rich Condition, Incomplete combustion, overlap.


Lean creats NOX.


I don't understand why this is such a magical mystery subject to So many people. Its just freakin chemistry.


To Directly answer You Bill, I Think that a little more advance May allow you to pass. perhaps Using a lower octane With the advance you have Now May Do it, but Either way, What You want to Do is get more of Your gas to finish combustion before the power stroke.

either a Faster burning ( lower octane ) gas or Earlier ignition ( Ignition advance ) Should help accomplish this.

Also, make Sure You Cat's are in Good Shape, And the AIR pump is workin.


the CAT's job ( well part of it ) is to Combust Unburnt HC's. it needs oxygen ( AIR pump ) to Do that.


Turn your FP down a bit, if you can, to lean it out. You could also open up a small vac leak someplace for the same effect. You Will see NoX Go Up, but HC should Go down a bit. You are really close there and have some room to work with on the NOX.



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

I had a similar problem with TX emissions test. A switch to synthetic oil helped a good bit, because it didn't burn so much as the regular stuff. Carb/fuel injector cleaner works too.

 

I'd try the 195 thermostat and maybe one of the alcohol suggestions, prolly w/ the 87 octane as well.
Beyond that, he has a SD TPI, you cannot create a vacuum leak in the traditional sense to lean it out. All a vaccum leak will do is lower your IAC counts. Also, you can't increase th idle speed either without getting into the chip either, if you turn the throttle stop in the computer will compensate down with the IAC.
It is also possible that your O2 sensor is failing, if it's never been replaced, now might be a good time to do that.
...ed

 

Also, forgot to add that turning the FP prolly won't help either. In closed loop the computer will automatically compensate for 14.7:1. In fact, dropping the FP may increase emmisions due to worse atomization.

 

Bort... no offense but a if you have too much air (O2) the the fuel (HC) will not burn... you can get a high hc reading w/ too much fuel but the CO will go through the roof... NOX is created by high combution chamber temp and pressure... in the readings that were posted the co was below the limit so a rich condition is not indicated...

also what I was saying was that there is not a lean condition present. as well it is not overly rich... so the suggestion I made was to check the compression to make sure there is not a weak cylinder and at the same time you would be inspecting the plugs to see if theree was a variance in the fuel distribution... eliminate the basics beefor you go to the other side of the troubleshooting, as in mods (the rocker ratio) or electronics (as in lazy o2 sensor)...

zroc

[This message has been edited by zroc (edited April 25, 2001).]

 

Here is what you do:
1. Check if your O2 sensor is slow, i.e. the rich/lean flag switches slowly.
2. Make sure your coil is in good condition, you can try an Accell 45,000 volt coil for $45.00 (or even an MSD 6AL)
3. Open your plug gap to .055ths
4. Install the 195 degree thermostat.
5. Make sure engine is at full operating tempature and get the trans got too by putting a load on the trans while holding the brakes, this will heat up the torque converter and make it more efficient
6. Check you EGR valve (more for NOX)
7. You need to remove your CATS and have them cleaned. I am not sure what type of solvent to use, but this will increase their efficency.
8. Make sure the airpump is working properly
9. Last, if you have headers you might want to try wraping them or having them coated.

Paul

 

One thing I left out, have your injectors professionally cleaned, like the 3M injector cleaner that the engine rums off of.

Paul

 

Hi folks,
I did not want to make the message to large, so I did leave some information out. First, I have headers,(SLP Hot Jet coated), TPI, 52M TB, ported headed and base, SLP Runners, MSD 6A, MSD coil, new Oxygen sensor (500 miles), no fail codes (custom Chip- Superchip - I believe some fail codes are overridden), 24 lbs injectors, and adjustable Fuel reg (42Lbs).
I will try some of the approaches discussed and let you folks know how it turns out.
Talk to you later
Bill

 

I had the same problem in Colorado trying to pass. I have nothing stock on my engine except the ECM, Q-jet and intake manifold. I replaced my chip with my stock GM chip, put in HIGH octane with a bottle of octane booster, replaced my t-stat, retarded my timing to factory specs, turned down my IAB and idle mixture screws, changed my Vapor Canister Filter, and just made sure it was tuned good and passed. I was without the pulse air (smogpump), and the Thermac aircleaner crap. You could put the factory aircleaner w/ the Thermac on for safe measure though. I have heard of the alcohol helping, but don't know personally. I might also replace the O2 sensor for the $20 it costs. It will help ensure your car is running good.

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Formerly known as 1984L69Z28

1984 Z28 - L69 optioned, 350HO w/ Trick Flow Heads, Drop Forged Lunati Crank, Crane Cam and 1.5 Roller Rockers, Stock Z28 Intake Manifold, Highly Tweaked Rochester Carb(700cfm), K&N Filter, ThermoMaster Chip w/ 160 Stat, Comp Headers, 3" Stainless Dual Exhaust w/ no Cat & Dynoflow Muffler, 4 wheel disc brakes, etc....

God bless us father, son, and holy ghost....whoever goes the fastest wins the most!!

 

bill- use the colemans fule the way the guy said and you will pass with more than flying colors... just mke sure ya run that tank real empty and fill up with premium, throw some dry gas in it, and away ya go....

the alchohol like rubber, but if its not in there long it wont hurt anything.

just remmeber, you can make just about anything pass... been there done that!

Steve

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86 Firebird, LG4, t-tops, 2.73 open rear, SLP 3 inch cat back exhaust, catco cat, 1 inch carb spacer, Fiberglass cowl induction hood, Formula wheels, vette servo.

Current Plans: Waiting on: rear end parts- upgrading to 373's, 28 spline axels, slp zexel torsion posi, and a disk brake setup. Also have lowering springs, front struts, and hopefully a new mild 350.


My Webpage- Battle of the birds, My own Thirdgen Page, still under construction, http://www.geocities.com/soares711/index.htm

88 Firebird Formula- deseased 2/9/99- 305 TPI, SLP 3 inch exhaust, SLP Intake runners, SLP cam, 3.45 BW disc brake posi, WS6, NOS, and all that good stuff, 13.8 on the motor, 12.89 on NOS and slicks! Hit by what else!?!? a FORD EXPLORER!!!!!!