First, let me give you the vitals:

-1983 Z28 305 H.O.,(L69), 103,000 miles, Q-Jet,Borg-Warner 5 Speed, 3.73:1 one legger.


-Engine rebuilt (.030 over) 200 miles ago

-Compucam 2040

-rebuilt carb (Autozone)

-new O2 sensor (Bosch)

-new CTS

-new plug wires, plugs, dist cap, rotor, igition pick-up coil

-original single exhaust with mono cat

-Mixture control solinoid set at 30-35 degrees with Idle at 800 RPM (slightly irratic)

-Cooling Fan switch set at around 210 Degrees

- Air going to Cat full time.

RESULTS:
HC was 4.4597,and the limit is 2.0

CO was 19.2880, and the limit is 30.0

N0x was 6.2971, and the limit is 3.0

- I'm thinking it's a partially clogged Cat because it is an original, but I'd rather not take a blind guess. Suggestions????

------------------
-1983 L69 Camaro Z28 305 H.O. (Bored .030 over,Teflon oil seals,Melling H.V. oil pump,Hyperetic pistons,chrome-moly rings,2040 Crane compu-cam) T-tops, 3:73 Open rear, BW T-5, Rebuilt E4ME 4 Barrel, Duel Snorkle Air Cleaner w/K&N Filter , Rhino Clutch, Crane 2040 Compu-cam, LS1 valve springs, porting, PST front end kit with new springs, and runs awesome!! Now for paint, interior, etc...etc.....Future Mods: Get rid of the 100 or so interior rattles.

[This message has been edited by Confuzed1 (edited September 08, 2001).]

[This message has been edited by Confuzed1 (edited September 08, 2001).]

 

Hydrocarbon failures mean unburned gasoline is passing through the engine and entering the exhaust. The three most common causes include ignition misfire, lean misfire and low compression (typically a burned exhaust valve).

Ignition misfire can be caused by worn or fouled spark plugs, bad plug wires or a weak coil. Lean misfire results where there’s too much air and not enough fuel, so check for vacuum leaks, dirty injectors or a fuel delivery problem. In addition to these, hydrocarbon failures can also be caused by oil burning due to worn valve guides, valve guide seals and/or rings.

Oh, and NOx could be a problem with the EGR, typically all three are too high if the catalytic converter is bad. Sometimes a faulty sensor can cause the car to stay in open loop and destroy your emissions, but since you've changed so many sensors I would think that the cat would be a good place to start.

[This message has been edited by rezinn (edited September 08, 2001).]

 

Thanks for the awesomley quick response Rezinn. A couple of other things:

I have CCC. No "Check Engine" light.
-Checked for codes - only 12 (normal)

I've replaced intake gaskets twice - because it seems to idle irratically - it "surges" slighly when idling (flutuates between 750-900 RPM's) **Camshaft maybe???


Oh - and I don't have injectors - (Q-Jet)

Also I replaced the EGR valve recently - Also an Autozone replacement. NOTE: This replacement wasn't a direct replacement - (it came with different sizes of "orfices" , and I matched the one closest to stock)


---I'll check out a couple of things you mentioned, like the EGR - but I have verified that the diaphram isn't blown, and the passages are clear. -

Otherwise, I'm very impressed with it's power. (I've owned slower 350's)

I'm positive I have no misfire. I'd hear that at idle.
I would hope that the compression isn't low either - Complete rebuild was done including new pistons - the works.


- Still open for any further HELP!!!!

 

You can also get unburned hydrocarbons in the exhaust by excessive cam overlap, but I doubt the Compucam would have that problem.

I know you said it was just rebuilt, but a compression check would be a good idea to insure it was done correctly.

About the only other thing that comes to mind is the fresh rebuild. It may not be broken in sufficiently. If that is the case, put a few hundred more miles on it, change the oil, and try again.


------------------
82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

Thanks for the suggestions. I'm really starting to lean towards the "lean misfire" thoery that REZINN (cool name BTW) suggested. I seriously doubt there is anything wrong with compression. Like I said , the car runs great and has no "check engine" light or codes. (except for 12)

I drove the car again today to see what a replacement CAT would cost me, and the cheapest I could find is CAR-X.....$197.00!!!!!!
Anyways, I also noticed my idle is now sitting at 1000 RPM....was 800 yesterday.....maybe a vacuum leak could cause this? (lean misfire)? Maybe I'll rip the stupid intake off AGAIN and change the gasket AGAIN.

What do y'all think??




------------------
-1983 L69 Camaro Z28 305 H.O. (Bored .030 over,Teflon oil seals,Melling H.V. oil pump,Hyperetic pistons,chrome-moly rings,2040 Crane compu-cam) T-tops, 3:73 Open rear, BW T-5, Rebuilt E4ME 4 Barrel, Duel Snorkle Air Cleaner w/K&N Filter , Rhino Clutch, Crane 2040 Compu-cam, LS1 valve springs, porting, PST front end kit with new springs, and runs awesome!! Now for paint, interior, etc...etc.....Future Mods: Get rid of the 100 or so interior rattles.



[This message has been edited by Confuzed1 (edited September 10, 2001).]

 

hey summit sells high flow cats starting at like $70 or something. I think direct replacment for our cars was like $115 or so. So try summit and look at the catco cat.

www.summitracing.com

 

Problem is, since it's a L69 model (H.O.), it has this gigantic cat with a 4-bolt flange on both ends. Supposedly, it's the same cat that was used on the corvettes around '82. A muffler shop also told me that the older pellet-type of cat that's on my car now, rarily clogs. Is that true? Anyone ever hear of that?

How about the symtoms I listed above? Think it's a vacuum leak or what? I plan to change the gasket tomorrow unless there's something I'm missing.......

------------------
-1983 L69 Camaro Z28 305 H.O. (Bored .030 over,Teflon oil seals,Melling H.V. oil pump,Hyperetic pistons,chrome-moly rings,2040 Crane compu-cam) T-tops, 3:73 Open rear, BW T-5, Rebuilt E4ME 4 Barrel, Duel Snorkle Air Cleaner w/K&N Filter , Rhino Clutch, Crane 2040 Compu-cam, LS1 valve springs, porting, PST front end kit with new springs, and runs awesome!! Now for paint, interior, etc...etc.....Future Mods: Get rid of the 100 or so interior rattles.

[This message has been edited by Confuzed1 (edited September 11, 2001).]