Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

EA81 MASSIVE backfireing problem...


  • Please log in to reply
13 replies to this topic

#1 GeneralDisorder

GeneralDisorder

    Elite Master of the Subaru

  • Members
  • 20,279 posts
  • Portland

Posted 07 November 2003 - 09:06 PM

I've got REALLY horrible backfireing on the Brat - I've removed, cleaned, and checked the operation of the EGR valve - looks good, and works good. I've removed, cleaned and checked the operation of the anti-backfire soleniod - also should be fine.

I recently blew an air suction valve, and had to replace that, and the silencer as it was melted. Those seem to be working fine, but some plastic got sucked into the carb.... I dug out all the plastic I could see, and she runs fine now - except for the backfireing.

The backfires are so bad, that my passenger the other day thought he had been shot, and it's blown about five VERY LARGE holes in the muffler.

What to do? Time for a weber? I had small backfireing on my wagon, and when I put the weber on, it all went away - never heard another peep out of it.

I don't really have the money for a weber right now - can anyone recommend a good brand of rebuild kit for the hitachi? I can rebuild it myself, and have some experience along those lines, but I don't know where to get the rebuild kit. Also - specifically what in the carb could be blocked that would cause this backfireing? I'm guessing some plastic has eluded me......

GD

#2 Qman

Qman

    Happiness is... no lag!!

  • Moderator
  • 11,113 posts
  • Sumner

Posted 07 November 2003 - 09:48 PM

Rick, try to follow this but it's kind of complicated. I hope I can explain it clearly.

At the air suction valve connects to the plastic bell. Take that apart and stick a quarter in there. Just to test it start it up and see if it backfires. This trick was told to me by someone who has done it a number of times. It may or may not work. But, it's worth a shot. If it solves the backfire then I'd just disconnect that system.

Ken

#3 GeneralDisorder

GeneralDisorder

    Elite Master of the Subaru

  • Members
  • 20,279 posts
  • Portland

Posted 07 November 2003 - 10:01 PM

I think I see what you mean - the quarter blocks the ASV from taking in any air right? I'll try that out tomarrow - in fact, I'll have to block off both ASV's I suppose in order to fully test that theory. Thanks for the tip.

GD

#4 RallyKeith

RallyKeith

    Got Subaru(s)?

  • Members
  • 1,479 posts
  • Reading, Pa

Posted 07 November 2003 - 10:18 PM

I had the exact same problem! EXACT! Blew apart my muffler at the seam, and even blew apart the honeycomb inside the catalytic converter. The trick Qman suggested will fix it. I replaced everything in my system and could never figure it out. Only thing I didn't replaced was the antibackfire valve since it tested fine and cost a ton of money.

Keith

#5 VABrat

VABrat

    New User

  • Members
  • PipPip
  • 17 posts
  • Round Hill

Posted 08 November 2003 - 02:47 PM

Hi Brat Dudes.

Am Having a backfire problem, as well. I'm just a Sunday afternoon mechanic, and I'm not sure where, in that mess of vacuum connections, the air suction valve is. Can anyone help this duffer?

#6 Snowman

Snowman

    Midnight Passenger

  • Members
  • 3,538 posts
  • Haines

Posted 08 November 2003 - 04:52 PM

The ASV connects to the exhaust ports on the bottom of the heads with metal lines about half an inch in diameter. The valve itself should be on the passenger side, right behind that head. It is inside a canister about the size of a soda can but shorter.

#7 Meeky Moose

Meeky Moose

    Subaru Master

  • Members
  • 2,343 posts
  • Grants Pass

Posted 08 November 2003 - 06:15 PM

so this is a backfire when ya let off the gas right?

cause thats what i'm gettin now since the engine swap.. the swapped in engine had one asv on it, so i had to use one off my other engine, so maybe the asv is bad on my spare engine that i put in?

cause the old engine never did it at all...

#8 GeneralDisorder

GeneralDisorder

    Elite Master of the Subaru

  • Members
  • 20,279 posts
  • Portland

Posted 08 November 2003 - 07:50 PM

Well snowman is mostly correct - the ASV (or ASV's) is roughly where he described, and it could be on either side - passenger or driver, or both. Also - on EA81's, it's not inside of anything - it's just sitting there by itself - couple of bolts hold it to the intake manifold. It could also have a vacuum line attached to the top of it. From it, there is a hose connecting to a black plastic houseing, which is sort of a muffler for the valve. If you remove this muffler from the valve with the engine running, you will hear the difference - it's MUCH louder. This is also where you should put the qaurter. I have yet to try it - I've been at National Guard drill all day today, and now I'm tired.....

I don't think the cause of the problem is actually the ASV's, but rather an effect brought on by them working correctly, and introducing too much unburnt oxygen into the exhaust stream. If this oxygen is not used by the cat, then it causes an explosive mixture of fuel and air in the tailpipe - which spontaneously ignites when exposed to the hot exhaust. I have a feeling the problem is actually several things - possibly a weak cat, combined with a carb that is running too rich. My EGR is fine, and my anti-backfire solenoid checks out, so that is my hypothesis at this point. We'll see if reducing the amount of oxygen in the exhaust by blocking the ASV helps or not. I think if it does, I will simply remove the system entirely.

GD

#9 VABrat

VABrat

    New User

  • Members
  • PipPip
  • 17 posts
  • Round Hill

Posted 09 November 2003 - 06:01 PM

All,

Thanks for the tips. Yes, backfire problem happens after accelleration when you let off the gas. I have an anti-afterburn valve on order (exspensive sucker) and should be in within a few days. Will let you all know if this solves the problem--from what I'm hearing, I just wasted a buck and a half. Have to get the Brat thru emissions within the next few weeks (pain) but if I get it to pass, I'm planning on sinking some bucks into this project--rust removal, paint, new exhaust, etc.
Sub friends--I cant get out of the parking lot without someone asking me if my Brat is for sale. What is it about this car that has captured the imagination? Maybe the fact that I have 230,000 miles and the EA 81 is still not burning one drop of oil!

VABrat

#10 Meeky Moose

Meeky Moose

    Subaru Master

  • Members
  • 2,343 posts
  • Grants Pass

Posted 09 November 2003 - 06:05 PM

well fixed my backfire.. all teh emissions stuff was just hangin really when i got the car, and with teh weber alot of it doesn't hook up anymore..

but i took the 2 lines that come from the ASV's and hooked it into a tube that came outa the intake.. seemed to have fixed the backfire and the rough idle.. not sure what that line is for so dunno if it should be there or not.. going to dig in my FSM and figure it out..

#11 GeneralDisorder

GeneralDisorder

    Elite Master of the Subaru

  • Members
  • 20,279 posts
  • Portland

Posted 09 November 2003 - 10:43 PM

Ok - just put the quarters to use in my ASV system, and the backfires are COMPLETELY gone. I talked to Mudrat on the phone, and he informed me that the actualy problem is likely the exhaust gaskets, or a hole in the Y pipe before the cat. This is sucking air into the exhaust stream and coupled with the air from the ASV system, is enough to cause the backfireing. Take away the ASV - problem is gone. Fix the exhaust leaks - problem also gone. So now I'll need to be putting on a muffler, and when I do, I can take a look for holes, and replace the gaskets.

Also - the quarters fit well in the ASV body itself, on the head side. You can just slip a quarter down past the threads, and then thread the pipe back on the valve - thus disabling the system without really removing it. Good if you want to pass emmisions later on, but don't want to fix a bad ASV right now, or fix exhaust problems. Really neato trick actually - Thanks Ken.

This one should go into the repair manual......

GD

#12 Oregonboy1

Oregonboy1

    USMB Regular

  • Members
  • PipPipPip
  • 85 posts
  • Billings

Posted 09 November 2003 - 11:39 PM

I just got back (Sunday night) from having my car towed to a shop. I was driving my 84 GL wagon to the gas station, and as I started to accelerate from a light, my car died. As I was trying to start it again, the car backfired! It sounded like an M80 going off. I then had to push the car to the side. I tried to start it again, and AGAIN it backfired! This time even louder!

A guy down the street ran to my car telling me that I probably blew my engine up. I don't think I did, but I did blow the seam heck out of my muffler.

GD, maybe I can stop by sometime and you can show me how to do that quarter trick.

Derek

#13 GeneralDisorder

GeneralDisorder

    Elite Master of the Subaru

  • Members
  • 20,279 posts
  • Portland

Posted 10 November 2003 - 12:04 AM

You might have blown an ASV, and sucked a bunch of plastic into the carb - sounds plausible. Maybe not tho. Don't take it to a shop! There's plenty of us board members around that could help you fix it yourself.....

GD

#14 VABrat

VABrat

    New User

  • Members
  • PipPip
  • 17 posts
  • Round Hill

Posted 11 November 2003 - 06:18 PM

I love this message board! Just took my gen 2 Brat for emissions test--to the Sub Dealer in town--what a huge mistake! they told me they couldn't even run the test until I gave them 600 bucks to replace the Y pipe. (after I told them this was a likely problem to my backfire problem) I'm going to try and find the hole, clamp it, and see if this solves problem. Unfortunately, I cant do the quarter trick until I pass emissions. Another problem which I knew about is a rust hole in the gas tank. Fuel system not holding pressure. They wanted me to by a new gas cap. If you want it done right--If you resent being raped by so-called mechanics--you need to do-it-yourself.

I do have another option--thank the Lord--my son lives in neighboring Clarke County, VA, and they dont require emissions test. I'm going to give him the Brat, get plates there, and stop worrying about it. Then I could put on a webber and forget the problems.

Thanks again for all the great advice

VABrat




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users