karinvail Posted March 26, 2005 Share Posted March 26, 2005 Ok, I have been reading the archives and checked everything that was talked about in previous threads - set timing, new vaccuum hoses on anything that looked like it possibly might need it, new manifold gaskets (at $5 ea!), no exhaust leaks, decent gas mileage (I'm guessing around 25, could be better), premium gasoline always, new spark plugs, good cap/rotor, good plug wires. I know it's this loud @$$ exhaust/muffler that is causing the backfire, and I'd like to remedy it ASAP. The exhaust is made from two exhausts - part from my 'donor' car and part from my car. Custom Y-pipe and muffler from the donor car, middle section from my car. Cats removed. It's just pipe down to big muffler with a HUGE tailpipe. The muffler shouldn't even be called a muffler because it doesn't muffle much at all I don't even see baffles in it. I love the looks of the muffler, and the sounds of it when the car is idling or low RPM's. (Doesn't sound like a 4cyl!) But, higher RPM's and it's giving me a headache, PLUS backfiring when shifting and decelerating. Always it's a pop-pop-pop-pop, and sometimes it's a BANG between shifts. Can I add something in the exhaust line that will help? Or is there a different (but still cool looking/sounding) muffler that I can put that it won't backfire? Hubby suggested a cherry bomb, but I would bet it would be the same? I would love to be able to keep the muffler I have (it's shiny chrome and looks good!), and just add something else if I could. I hope anyhow! Quote Link to comment Share on other sites More sharing options...
NorthWet Posted March 26, 2005 Share Posted March 26, 2005 I doubt that mufflers will help, as it sounds like you have a classic case of running overrich mixture on overrun. this is caused by high vaccum conditions sucking excess fuel through the idle-circuit of the carb. Usually, cars have a dashpot or similar to keep the throttle from slamming closed when you suddenly get off of the gas. Some carbs also have an idle-circuit shutoff solenoid that takes care of this. I would look to see what your car is supposed to have and get it working. I blew up a muffler on my 510 due to this problem. Quote Link to comment Share on other sites More sharing options...
karinvail Posted March 26, 2005 Author Share Posted March 26, 2005 I doubt that mufflers will help, as it sounds like you have a classic case of running overrich mixture on overrun. this is caused by high vaccum conditions sucking excess fuel through the idle-circuit of the carb. Usually, cars have a dashpot or similar to keep the throttle from slamming closed when you suddenly get off of the gas. Some carbs also have an idle-circuit shutoff solenoid that takes care of this. I would look to see what your car is supposed to have and get it working. I blew up a muffler on my 510 due to this problem. I am totally confused now, LOL. The carb that we saved from my old engine was a new rebuilt carb - do you think that switching carbs might help then? Quote Link to comment Share on other sites More sharing options...
Skip Posted March 26, 2005 Share Posted March 26, 2005 Karin Not that I want to confuse you more than you are but I have to disagree with Northwet I have never seen a Subaru that used it's anti diesel solenoid to prevent back fires. It's function is to prevent run on after the key is switched off. The backfire sound like a classic case of the air suction reed valves going bad. This condition can lead to the silencer melting and then carb ingests this melted plastic - causing a labyrinth of problems Quote Link to comment Share on other sites More sharing options...
NorthWet Posted March 26, 2005 Share Posted March 26, 2005 ... I have to disagree with Northwet... No worries! I disagree with me at times. The carb on my Nissan engine uses a carb mounted solenoid to cut idle circuit during deceleration, but that doesn't mean that Subaru uses something similar. Skip's idea about the air valve is probably a good thing to check, and could definitely explain where the needed oxygen is getting in; only one of my Subes have these valves, so I didn't think of them. (I personally think that the mixture is still going rich, but opinions are like ***, we all have one. Some say that I have at least two! ) anyways, it should be easier to check the valve reeds than hunt down cause of rich mixture. Quote Link to comment Share on other sites More sharing options...
karinvail Posted March 26, 2005 Author Share Posted March 26, 2005 OK, yeah, now I am confused Where do I find the 'air suction valve reeds'????? I have never heard of such a thing, LOL. I'm guessing it's in/on the carb???? Boy, am I learning a LOT from this site. WOW. I am even dreaming about Subaru's, LOL. Not good dreams either - mechanical/working on them dreams I know that once I get all the things fixed on this car that was neglected for so long, that it will be as reliable as any of my other Soob's have been though Quote Link to comment Share on other sites More sharing options...
NorthWet Posted March 26, 2005 Share Posted March 26, 2005 Not on the carb, but connected to the intake and the exhaust. Skip/others can tell you where to look on an EA82 (I don't have them), but if you look at your exhaust ports there should be one or more large (1" dia. ?) steel tubes that connect to the exhaust port area and travel upwards towards the air filter. Somewheres there should be a small-fist sized hunk of metal that is the reed valve housing. As I said, others know more... Quote Link to comment Share on other sites More sharing options...
Skip Posted March 26, 2005 Share Posted March 26, 2005 Karin Pat did an exclenent job of giving you a sure fire way of finding them here is a post about my episode http://www.ultimatesubaru.org/forum/showthread.php?t=2569&page=1&pp=20&highlight=reed+valves Here is a link to the Ultimate Subaru repair manual. (found at the top of the page) article by Shawn http://www.ultimatesubaru.org/forum/article.php?a=72 And here is one for reading about some "other" ways to fix or test if it is the problem http://www.ultimatesubaru.org/forum/showthread.php?t=18913&highlight=backfire Hope this helps Quote Link to comment Share on other sites More sharing options...
karinvail Posted March 26, 2005 Author Share Posted March 26, 2005 oh, man, my head is spinning with all that info! dang, and we just sold that parts car with the engine with the cracked block too (and it probably had that part on the engine that DIDN'T backfire, grrr.) Is this the air valve? The silver part right in the middle of the pic? I had to unhook that black canister (moved it to the left - what IS that part too?) that goes in the hanger there, and has a hose that goes to the air filter..... Is there one on both sides or just the passenger side? I peeked on the drivers side, but it's a lot more crowded on that side and I didn't see one..... Quote Link to comment Share on other sites More sharing options...
subie94 Posted March 27, 2005 Share Posted March 27, 2005 had a back firing prob on my 86 gl,turned out to be what my mech called a anti-back fire valve.of course he never showed me where it was located.of course i enjoyed it but not my neighbors. was told by a friend that was driving behind me that when it backfired it through out a small flame---cool! Quote Link to comment Share on other sites More sharing options...
NorthWet Posted March 27, 2005 Share Posted March 27, 2005 ...Is this the air valve? The silver part right in the middle of the pic? I had to unhook that black canister (moved it to the left - what IS that part too?) that goes in the hanger there, and has a hose that goes to the air filter..... Is there one on both sides or just the passenger side? I peeked on the drivers side, but it's a lot more crowded on that side and I didn't see one..... That looks to me like the ASV (again, I am no expert on carb'd EA82s). According to my '85 FSM, the Cali version had only a driver's (left) side ASV, while the 49-state versions had variations that used ASVs on both heads. Some confusion might have occurred duriing your engine swap, so watch for mismatch issues. The black canister should be the silencer, which I believe is what Skip warned could/would get melted and cause FOD to your carburetor. Skip, thanks for the links. I had just seen Shawn's writeup last week, but couldn't remember who/where to recommend it to Karin. Quote Link to comment Share on other sites More sharing options...
torxxx Posted March 27, 2005 Share Posted March 27, 2005 carb expert here. You need to plug off the ASV hoses. Unplug the hose at the big black canister thing. (the silencer) now get some pvc end caps. thread it on to the hose. this will fix that popping and backfiring. Your exhuast is getting too much air, thus making the popping and the backfire when you shift. Quote Link to comment Share on other sites More sharing options...
karinvail Posted March 28, 2005 Author Share Posted March 28, 2005 carb expert here. You need to plug off the ASV hoses. Unplug the hose at the big black canister thing. (the silencer) now get some pvc end caps. thread it on to the hose. this will fix that popping and backfiring. Your exhuast is getting too much air, thus making the popping and the backfire when you shift. So, plug it between the ASV and the black canister? Is this just a band-aid fix though? I'd like to get the best fuel mileage possible, and if plugging it will hurt fuel economy, then I'd only do it until the part came in (assuming I have to order it). I am not in a part of the state where we do emmissions testing, so that is not a concern - just fuel economy and how well it runs. Quote Link to comment Share on other sites More sharing options...
TomRhere Posted March 28, 2005 Share Posted March 28, 2005 Went thru this meself when I ditched the cat on the '82. You need to block the steel pipes shown in your pic, either at the exhaust port/Y-pipe connection, or where they go into the piece shown in pic. Did mine at the exhaust port. GeneralDisorder often stated that a quarter would fit enough to block port, just put in in-front of tube, where it attaches to exaust port. I just cut the tube and welded in a section of a bolt that I had cut down, in the tube, close to fitting. Quote Link to comment Share on other sites More sharing options...
Numbchux Posted March 28, 2005 Share Posted March 28, 2005 And here is one for reading about some "other" ways to fix or test if it is the problem http://www.ultimatesubaru.org/forum/showthread.php?t=18913& that is my thread...still running just a Y-pipe, but disabled the ASV's as described in both threads, and running the Y-pipe of my loyale, which has a good cat, and may be of slightly different design (since it's for an FI motor, not a carbed one). the backpressure of a good cat, instead of a rotted out one, helped a TON. Quote Link to comment Share on other sites More sharing options...
85Sub4WD Posted March 28, 2005 Share Posted March 28, 2005 had a back firing prob on my 86 gl,turned out to be what my mech called a anti-back fire valve.of course he never showed me where it was located.of course i enjoyed it but not my neighbors. was told by a friend that was driving behind me that when it backfired it through out a small flame---cool! there is actually an anti-backfire valve - it is located near the charcoal canister I think that torxx is right - mine popped whenever I released the throttle - did not go BANG, just sort of sounded like an exhaust leak ( put, put, put ) I doubt that running without your ASV's should not cause any change in fuel economy - just emissions Quote Link to comment Share on other sites More sharing options...
karinvail Posted March 29, 2005 Author Share Posted March 29, 2005 Well, we took off the ASV on the passenger side to inspect it - and it looked perfectly intact and assumed it just wasn't working even though it's not broken. The ASV on the driver's side is under the distributor and silencer - and both would have to be removed to get that one off to inspect it since the bracket bolts are inacessable without removing them (which we did NOT want to do!). So, we made some 'plugs' out of sheet metal and blocked the ASV's off at the manifold. It made a big difference - it doesn't pop or backfire when accelerating/shifting, but it does still pop a little decelerating (which I am sure is the anti-muffling muffler.) No more shot gun going off anyhow! Quote Link to comment Share on other sites More sharing options...
gunslinger Posted March 29, 2005 Share Posted March 29, 2005 Well, we took off the ASV on the passenger side to inspect it - and it looked perfectly intact and assumed it just wasn't working even though it's not broken. The ASV on the driver's side is under the distributor and silencer - and both would have to be removed to get that one off to inspect it since the bracket bolts are inacessable without removing them (which we did NOT want to do!). So, we made some 'plugs' out of sheet metal and blocked the ASV's off at the manifold. It made a big difference - it doesn't pop or backfire when accelerating/shifting, but it does still pop a little decelerating (which I am sure is the anti-muffling muffler.) No more shot gun going off anyhow! after reading everyone's info, sounds like you solved it or close to it. swervey and i both had the prob on carbs. swervy had fun with it till he blew the back of his brand new muffler out.... we both weld so we unbolted the hard steel lines coming off of the heads by each exhaust port and pinched/welded the lines shut @ approx 2". no probs after that. you get rid of the whole system that way. also, the muffler IS too big/too much flow. my 87 yota had the same prob when i put a header and too large exhaust on it. put a higher flow muffler on it but not a really big one/or one with no baffles. you need some backpressure with these subie motors. hope this helps. Quote Link to comment Share on other sites More sharing options...
karinvail Posted March 30, 2005 Author Share Posted March 30, 2005 after reading everyone's info, sounds like you solved it or close to it. swervey and i both had the prob on carbs. swervy had fun with it till he blew the back of his brand new muffler out.... we both weld so we unbolted the hard steel lines coming off of the heads by each exhaust port and pinched/welded the lines shut @ approx 2". no probs after that. you get rid of the whole system that way. also, the muffler IS too big/too much flow. my 87 yota had the same prob when i put a header and too large exhaust on it. put a higher flow muffler on it but not a really big one/or one with no baffles. you need some backpressure with these subie motors. hope this helps. Ya, I was kinda hoping for a sportier sound and a little more ''oomph'' with this muffler. Got a little more than I bargained for though Quote Link to comment Share on other sites More sharing options...
swervey87gl Posted March 30, 2005 Share Posted March 30, 2005 Ok, I have been reading the archives and checked everything that was talked about in previous threads - set timing, new vaccuum hoses on anything that looked like it possibly might need it, new manifold gaskets (at $5 ea!), no exhaust leaks, decent gas mileage (I'm guessing around 25, could be better), premium gasoline always, new spark plugs, good cap/rotor, good plug wires. I know it's this loud @$$ exhaust/muffler that is causing the backfire, and I'd like to remedy it ASAP. The exhaust is made from two exhausts - part from my 'donor' car and part from my car. Custom Y-pipe and muffler from the donor car, middle section from my car. Cats removed. It's just pipe down to big muffler with a HUGE tailpipe. The muffler shouldn't even be called a muffler because it doesn't muffle much at all I don't even see baffles in it. I love the looks of the muffler, and the sounds of it when the car is idling or low RPM's. (Doesn't sound like a 4cyl!) But, higher RPM's and it's giving me a headache, PLUS backfiring when shifting and decelerating. Always it's a pop-pop-pop-pop, and sometimes it's a BANG between shifts. Can I add something in the exhaust line that will help? Or is there a different (but still cool looking/sounding) muffler that I can put that it won't backfire? Hubby suggested a cherry bomb, but I would bet it would be the same? I would love to be able to keep the muffler I have (it's shiny chrome and looks good!), and just add something else if I could. I hope anyhow! Yea. gunslinger hit it. Find the two pipes coming off of the head that are not the exhaust. Follow them up to the plastic boxes that are on each side of the back of the engine. Then the hoses that come off of those that feed to the air cleaner. PLUG THEM WITH MARBLES. yes it is a hokie way to fix it but it works till you decide to convert your car to FI. Enjoy your quiet subie then. Quote Link to comment Share on other sites More sharing options...
karinvail Posted March 30, 2005 Author Share Posted March 30, 2005 Yea. gunslinger hit it. Find the two pipes coming off of the head that are not the exhaust. Follow them up to the plastic boxes that are on each side of the back of the engine. Then the hoses that come off of those that feed to the air cleaner. PLUG THEM WITH MARBLES. yes it is a hokie way to fix it but it works till you decide to convert your car to FI. Enjoy your quiet subie then. We ended up pluggin them with sheet metal made into the shape of a small exhaust gasket (without the hole in the middle, LOL). I would LOVE LOVE LOVE fuel injection in my car - I would have NO clue how to go about it though - seems like it would be just easier to sell this one and buy one that already had fuel injection, LOL. Quote Link to comment Share on other sites More sharing options...
85Sub4WD Posted April 21, 2005 Share Posted April 21, 2005 I would LOVE LOVE LOVE fuel injection in my car - I would have NO clue how to go about it though - seems like it would be just easier to sell this one and buy one that already had fuel injection, LOL. http://www.ultimatesubaru.org/forum/article.php?a=61 I did it myself - not that hard, you do have to plug the pipes for the Air Injection system (which I assume you have already done - I fabbed aluminum coverplates plates out of scrapmetal), and from then on, it isn't so bad, especially if you have a donor car with a known working engine - the exhaust system connection is probably the hardest part - just make sure the ECU case is well grounded - I think the carb engine cams actually work very well with SPFI everything else - I just wish I had the 9.5:1 compression ratio (more power) - I normally around 25mpg in the city now vs. about 18 before Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.