Fast81

Just got back from the "sniffer shop" and didn't pass. I drove her around for 60 min to get all nice and toasty before the test. Had a 1/2 tank of reg unleaded, new cat installed. Only failed the CO.

reading limit
HC 85.5ppm 148ppm PASS
CO 2.63% 1.84% FAIL
NO 73.6ppm 1047ppm PASS
CO2 12.32%

No A.I.R. pump , no EGR



[Modified by Fast81, 3:09 PM 9/25/2003]

battsup

Hmm, that was the one thing i did pass, :lol maybe if you try cleaning out the carbon and also fill up with the highest octane gas u can get at the pump.

Gator81

Here's a couple of ideas.

Assuming your '81 is basically stock and has all the smog gear on it... and assuming your "check engine" light works and is not on...

You didn't say if the failed test was at idle speed or road speed. Where I live, you have to pass both at 1000 rpm and at 2500.

If the problem is at idle, I'd bet it's the idle air bleed valve, in the top of the carb. If it's never been tampered with, it probably isn't the problem, but I've never yet seen one that hasn't been "adjusted", and I've looked at dozens of 'em. Anyway, if it's been adjusted before, the tamper-resistant cover will be off and you'll be able to see the screw head. It's shiny chrome, with a single slot, and about the size of a dime or a little smaller. With the engine hot and running at idle, turn this screw in whichever direction will get you an increase in idle speed. Then, adjust your idle stop screw (on the driver's side of the carb, where the linkage connects) until the idle speed goes back down. You may need to do this cycle a couple of times.

If the problem is at road speed (2500 rpm or thereabouts) I would check the air system. There are three check valves that have to open to let the air pump push air into the exhaust to feed the cat. And they have to close to prevent hot exhaust from backing up into the air pump. If they stick shut, you don't get enough air for the cat. If they stick open, your air pump gets burned out.

I would also check to make sure you're getting EGR activation, and that the PCV valve is working properly. And just for a small margin of good luck, I'd make sure it had clean oil in the crankcase.

[edit] Oh, yeah, one other thing. I'd set the timing up above the stock 6 degrees at idle to at least 8, maybe 10. That will increase your idle speed, so you might need to do the idle air bleed valve and idle stop screw adjustments after you adjust the timing. If you haven't set timing on the '81 before, there's a wire with a plug on the side of the distributor that has to be unplugged to disconnect the computer from the distributore so you can set base timing. I can't remember for sure the color of the wire - I think's it's gray, but I'm just guessing.

Good luck! :seeya


[Modified by Gator81, 1:54 PM 9/25/2003]

Fast81

Gator -- I have a Holley Throttle Body Injection system. No AIR pump or EGR. Just a Cat. The test printout doesn't list where the failure occured, only that I exceeded the 1.84% standard by .79% (2.63-1.84=.79)

All I really need is to cut the CO down
Mods are listed in my sig

Tom454

Heads up... some people are on dial-up and have to turn sigs etc off or else they cannot use this web site. This sometimes contributes to confusion when questions are answered. I have had this problem myself. Just one of those things.

May not apply in this case... but I didn't see the sig either. Had no idea it was Holley instead of GM. I thought it was an awesome response. Oh well. :crazy:

Gator81

OK, then, so much for all that crap... (I don't have sigs turned on :) )

Well, all I can offer is that the TBI ought to be better at this than the E4ME, so I think you gotta look downstream from the induction system. The stock cat needs air to work at its best, that much is for sure. I hope that doesn't mean putting the air pump back on, but it might.

Can you adjust the Holley system to give you a leaner mixture during the test?

I would still have the timing up as much as your engine will tolerate at idle. Plus all the hoohah about clean oil still applies. Higher temperatures clean up the exhaust, but that applies more to HC than CO. Do you know where your temps are running during the test?

And now that I think of it, you might try the opposite tactic on the timing. I don't know why, because it's the opposite of what I understand about emissions, but I used to have an old truck that would only pass emissions if I retarded the base timing back to the point where the damn thing would barely run. It was a 1980, and had the cat removed, but would still pass the 1980 standards if the timing was set way back.

Sorry about all the off-target advice. :rolleyes: Good luck! :seeya

Jvette73

RETARD TIMING!!!!!! My 86 pont had all the emissions equip intact and functional but still would just barely fail with the timing set to specs. Got a tip from another forum member(Matt Gruber) to retard timing which I did. The factory setting was 8 and I retarded it to 2. That did the trick and significantly reduced the emissions output in all catagories. It passed with flying colors with the retarded timing even though it did not run all that good. After the test I re-set the timing to specs.

Master Ho

It might be worth checking into the gasoline additives made specifically for passing emissions testing. I've seen them in the local parts stores. YMMV.

Z-man

I agree that you might want to try retarding timing. Your HC might go up, but you have some room there.

BSeery

did you fail idle or loaded test?

BSeery

did you fail idle or loaded test?
I am guessing that you are running rich. Which version of the Holley TBI are you running ? The 4D, 4Di, or Commander950 ?

BSeery

did you fail idle or loaded test?
I am guessing that you are running rich. Which version of the Holley TBI are you running ? The 4D, 4Di, or Commander950 ?

If it is the 4D, you need to tune it with the *****.
4Di or C950 should self correct via the 02 sensor. Make sure you are in closed loop. If in open loop then you need to tune the map.

Jvette73

In my case, retarding the timing reduced all catagories, including the HC, which went down by more than 1 full gpm. I would recomend cutting the timing back 6 degrees from where it was on the first test.

Fast81

The stupid printout doesn't break out which phase I failed. The only info I have is what I originally posted.

I'm running the Holley 2Di without the closed loop add-on (ordered it yesterday).
I'm going to lean the fuel MAP some more and fill up with Super-de-duper Unleaded and try it again (failng is FREE).

BTW do those emissions fuel additives come with any guarentee, might try a can/bottle to tweak that last .79% of CO out of the fumes !!!!!! All I have to do is pass this once then I hit the magical 25 yr exemption (true duals here I come) :D

BSeery

I don't know if the higher octane is better. It burns slower, and is harder to ignite (hence why it will not ignite early (pre-ignition) and cause knock). To me, I would want my fuel to burn faster to get a complete burn and make sure I don't have any raw leftovers going down the tailpipe.

But I could be wrong.

Yep, work on that map and lean it out some. Just remember to record your old settings in case you want to go back.
I am going to be installing the C950 4 bbl system on my 1980, and I have to pass emissions every year from now till, well, ever. We don't have a 25 year exemption. AZ tests everything from 1967 and up.

Gator81

Ya know, I've always been puzzled by why it is that retarding the timing, way, way, back to the point where the rig will hardly run, seems to clean up the exhaust. But now you've given me a theory... maybe, by starting the fire so late in the cycle, we've still got fire going when the exhaust valve opens and the exhaust stroke begins. That means we've got live fire streaming out the exhaust ports and into the manifold, creating an effective afterburner, not unlike another catalytic converter. Whatcha think? Could that be what really happens?

Have you ever watched race cars on a road course, slowing down to enter a corner... they're completly out of the throttle, and the timing backs down, and there it is: fire coming out the tailpipe. And it stays visible right up to the point where they nail the throttle again.

Well, that's my theory, and I'm stickin' to it. At least until one of you smart guys shows me why I'm wrong... and that usually doesn't take long around here... :lolg:

BSeery

The fire in the pipes is from the raw gas going into the VERY hot pipes and burning in the pipes. There is a lot of raw gas right after they close the throttle as the air is cut off right away so it suddenly goes rich. The pipes are so dang hot that they will ignite any raw fuel. I would love to see what that would do to that dang emissions probe the put up the ol' tailpipe !

EDIT: Supposedly the A.I.R. system works with that and sends more air into the system at the exhaust valve to help continue the burning process. Helps get the mixture after the valve back to very lean so it burns fast and hot.


[Modified by BSeery, 10:26 AM 9/26/2003]

MN-Brent

I have seen first hand the effects of simply removing the vacuum advance to the distributor will take both needles (C02 and HCO) on the smog sniffer and drop them to almost nothing.

Brent....

Fast81

MN-Brent: please pardon my ignorance.
Is this something I can unhook (1 block away), plug and drive to the E-station ??? They don't even open the hood.