bdmartin

Yes - you can slip a quarter into the AIS valve body and thread the pipe fitting back on - that will effectively block the valve and will help with the backfireing.

GD

GD,

Now that I've passed emissions, is it possible and/or desireable to block that air injection system? Lots of backfiring still.

Thanks for all your help. It passed with flying colors this time.

The backfires are probably from too much fresh oxygen in the exhaust. Check the air injection system that I mentioned before and check for exhaust leaks.

Leaning out the mixture is only possible for the idle circuit - screwing it in (clockwise) will lean out the mixture.

I would retard the timing to 2 degree's or even 0 for the test. Retarding the timing will drive up the cylinder temps to your benefit.

GD

Rick,

I have replaced the front exhaust/catalytic converter with a magnaflow direct fit. As you suspected, my old one was pretty well burned out, with chunks of the honeycomb falling out when I removed it. Now it's rather LOUD and backfires quite a bit, but it seems to run better on the road. I plan on mixing in some denatured alcohol, as you've suggested, before I have it emmissions tested again. It still has some E85 gas mixed with regular unleaded in it, about 3-4 gal each. Is there anything else I can adjust to lean it out, and how far should I retard the timing when I do have it tested? Also, I've seen contradicting info online about the idle mixture screw. Is it clockwise leans out the mix, or the reverse? Thanks again for your help.

Brad

The vacuum system may be incorrect - but the only thing that really matters is that the EGR is supplied with late ported vacuum and is opening correctly. The rest of the vacuum system really doesn't effect emissions enough to matter.

There is a passive air injection system that supplies oxygen for the old cat's to work effeciently - a new cat wouldn't need it but if you are conviced the old cat is still good then this system must function properly. It consists of two reed valves that are hooked to metal pipes that run to spacers between the heads and the exhaust manifold. Look for the spacers and trace it back to the reed valves - pull off the plastic silencers while the engine is running and insure that you can feel/hear the exhaust sucking in air. If they have been blocked by a previous owner to prevent backfireing you will hear no change.

Similarly if the reed valves are broken you will feel raw (hot) exhaust - which will melt the plastic silencers and suck melted plastic into the carb....

E85 is corrosive and your fuel lines, etc are not rated for it. I would not use it at all.

I would start with 25% denatured alcohol and go from there. You can run up to 50% but the more you use the worse it will run - no power, etc. Also retard your timing to increase combustion and exhaust temps - this will drive up the cat effeciency and will help to kill HC's too.

Rick

Rick,

Thanks for the reply. Is there a possibility that my vacuum system is the cause of my problem? The reason I ask is that my car only has 105K original miles, and the entire exhaust system appears original and in excellent condition for a 27 year old car. Very little rust and no holes. There's no O2 sensor, ECC or EGI on this model. I have no problem replacing the cat, but I'm less than confidant that my vacuum system is 100% correct. Are there any comprehensive diagrams or pix showing where the lines go? Also, what mixture of Dentatured Alcohol/ fuel should I use, and is E85 fuel ok?

Thanks again for your time and expertise.

Brad

P.S. sorry for posting more than once, having trouble uploading message.

Hey Brad - I would say that your catalytic converter is probably toast - usually they are broken up inside or just plain burned out. I would start out with a new cat from ebay - welded into the exhaust as close as you can get it to the cross-over where the two runners from the heads meet. If that doesn't quite clear it up then start mixing in Dentatured Alcohol from home depot, etc - that stuff burns rediculously clean and although you will have to retune the idle some and it will run like crap - it will pass.

Rick

GeneralDisorder,

From reading your posts you seem to be quite well versed in all things Subaru. I'd like to ask your advice on my car. I have an 84 GL 4X4 Hatchback, 1800 ea81 with a hitachi 2-barrel. I just got it running after having the heads rebuilt, and rebuilding the carb myself. It seems to run well but failed emmissions due to high HC (4.48GPM / limit 3.0) and CO (39.32GPM / limit 30.0) readings. After draining the gas and replacing with E85 fuel it failed the retest as well. The readings were: HC - 11.729 (more than twice the first test) and CO - 3.026 (36GPM dropoff and well below limit) Apparently I still have to much unburned fuel. As far as I've read the only adjustment is the idle air/fuel mixture. Can u offer any advice on what I might look for to get the HC readings down? Any help would be greatly appreciated. Thanks, Brad

GeneralDisorder,

From reading your posts you seem to be quite well versed in all things Subaru. I'd like to ask your advice on my car. I have an 84 GL 4X4 Hatchback, 1800 ea81 with a hitachi 2-barrel. I just got it running after having the heads rebuilt, and rebuilding the carb myself. It seems to run well but failed emmissions due to high HC (4.48GPM / limit 3.0) and CO (39.32GPM / limit 30.0) readings. After draining the gas and replacing with E85 fuel it failed the retest as well. The readings were: HC - 11.729 (more than twice the first test) and CO - 3.026 (36GPM dropoff and well below limit) Apparently I still have to much unburned fuel. As far as I've read the only adjustment is the idle air/fuel mixture. Can u offer any advice on what I might look for to get the HC readings down? Any help would be greatly appreciated. Thanks, Brad