Carb keeps backfiring....??

[87gl]

Got an 87 Subaru GL, 4WD, 1.8 (non-turbo) carburated.

 

I got it running now, but at low RPM's, it has pretty much no power. The idle fluctuates between about 400 - 1000 RPM when its just sitting.

At high speeds, it seems to run fine. Once I get it up to about 3000 RPM's, or about 40 - 45 mph, it does okay, still not perfect, but it doesnt act like its gonna die or anything.

I have had about 3 people look at it, and nobody can figure it out, small town, and there are virtually no Subaru's in this town. Nobody has ever really worked on one.

The carb backfires too, especially after it is reved up to a high RPM, then as it is coming down, it pops out of the carb, and almost immediately dies.

We have checked the timing, seems to be right on, new plugs, cap + rotor. Wires are okay too.

 

Anyone have an idea? I put a new fuel pump on too, wondered if the pressure of the new pump was too high, could this cause it? The fuel system runs stock about 2.2 - 3.3 lbs of pressure, and the new pump I put on pumps 4 lbs. Would this make a difference?

 

Someone please, HELP ME!!!

 

If somethinks they know, they could also just take the car home for $350. There are some pics on this thread, and I can take as many more as anyone wants.

 

http://usmb.ultimatesubaru.org/forum/showthread.php?s=&threadid=7466

[GeneralDisorder]

Ya know - with the tach jumping you describe, and the lack of power, and the backfireing - it really sounds like your distributor is starting to go. Wiggle the shaft - there should be almost no play if it's good.

 

Possibility anyway. If that is the case - there should be someone in a close LARGE town that could do the shaft bushing for you. Cost around here is about $35

 

These guys can do it:

http://www.philbingroup.com/

 

GD

[87gl]

someone actually suggested that the distributor was bad. Would an 87 Subaru XT non-turbo with the 1.8 work in my car?

 

Let me know, I know where I can get one for around $30 out of a good running XT.

 

Thanks for the quick advice.

[87gl]

the distributor would cause the backfiring out of the carb too though?? that seems weird....but then again first car I have ever worked on that is this old, or that has a carb.

 

Let me know if anyone else has a suggestion.

 

Thanks again.

[MilesFox]

no, the xt dist will not work, being probably mpfi, having an optical disty.

 

an 85 or 86 carb disty will work on anything(i got one on an spfi motor with a carb down in a turbo car, running off the turbo's coil, mpfi harness still there) i got an 86 dist im my ea82 powered 83 wagon.

 

so if you cant find an 87, go with 85-86.

 

and the internals of the 85/86 carb is the same as a lot of ea81 dists also

[87gl]

what if the XT was carburated? Then would it work?

 

Does anyone have a good dist. they could sell me?

 

Let me know.

[MilesFox]

i dont think the xt came as carb. they were turbo, non-turbo mpfi, and xt6.

 

carbs lasted to mid 87. torbo has been around for ea82 since 85, and the 85-86 mpfi and turbo are pretty much based off the 83-84 ea81 turbo.

 

all 87 and up have the optical dist

 

but the 85/86 xt turbo has the same type dist, but with a knock control unit. i'm sure the mpfi xt would have the same dist, but no knock unit.

 

i have seen an 86 spfi, i dont recall the dist, but all other spfi has the optical type.

[MilesFox]

i put a carb on my throw-together just bought a car with no motor. it backfired didnt run right. by the 3rd carb, i turned the disty and it ran like it was supposd to.

 

advance the timing by turning the dist slightly to the RIGHT, se if it idles up a little. drive it around. tweak the timing until it seems to run the bedt. just keep a 10mm socket handy.

 

if it were a vacuum leak, it would want to idle faster. see if the idle changes when you hit the brake pedal. that will help a little in determining a vacuum problem. make sure al the connections around the air cleaner are connected, there is one underneath in the back of the air cleaner that goes doen to the framerail under the master cylinder.

 

there are 2 on the front, one can come off easily if the aorbox is moved for any reason.

 

carb toiming should be 8deg BTDC, test timing with the vacuum advance disconnected and the hose plugged.

[87gl]

i will try this, but if it doesnt work, I am just gonna give up on this!!! LOL

[Superoo]

1987 GL, my favorite and only Sube. Anyway what you are discribing is classic vacuum leak symptoms. With all the vacuum lines on a stock 87 it could be a little tough to find but somewhere you've got a vac hose loose or cracked. At least that's my guess. The primary indicator to me (and the reason I don't think that it's the disty) is the fluctuating idle (lean air fuel mixture) AND off throttle backfire. I'd bet if you do some searches on finding a vacuum leak you should be able to turn up some techniques for locating your problem.

Good luck!

LenHorn