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Rough running when accelerating


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22 replies to this topic

#1 sidekickin

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Posted 25 December 2003 - 09:08 PM

Hey guys,
Got another problem that I am hoping you can help me with. This one just developed a few days ago. Occasionally when the car is accelerating or under a load (going up a hill), the engine will start sputtering and running rough....like it is not getting fuel or the car has run out of gas. It will do this intermittently from time to time. When it does this it will do it for 5-10 seconds and be done. Otherwise this car runs perfectly. It idles perfect and performs perfectly. But it only does this when it is under a load. When it is doing this and I floor the pedal to kick in the 2-barrel, it runs fine and takes off. So I don't think it is the fuel pump or the fuel filter. Because if either of those 2 were bad, the problem would be aggravated when kicking in the 2 barrel and needing more fuel. It typically does this at a higher RPM range also, like when you are winding out the gears when accelerating. At lower RPMs it does not have a problem. It acts as if it is starving for gas....not like it is misfiring or anything. It has steadily gotten worse over the past week. Fuel filter has been replaced, along with dist cap, rotor, plugs, wires, and a new catalytic converter about a year ago. Car has a Hitachi 2BBL carburetor. Could this be a symptom of a carburetor problem or something else? Any help is greatly appreciated! Thanks.

Bill

______
1987 Subaru STD 4WD Hatchback
EA-81 w/hydraulic lifters
Hitachi 2BBL carb
Single range 4WD
133,000 miles

#2 Qman

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Posted 25 December 2003 - 09:17 PM

Fuel filters. Change both of them. Chances are that the rear filter hasn't been changed in a while. It starts as a little bog or hesitation under load and gets progressively worst.

#3 Stupidru

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Posted 26 December 2003 - 01:37 PM

Mine just started doing the same thing...I was thinking I got a batch of bad gas...cause I only have one filter (& that was changed 8k ago)..except for that stupid vapor seperator thingy. hhhummmmm????

#4 sidekickin

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Posted 27 December 2003 - 05:02 PM

Still have my problem....some days it is worse than others. Let me know if you figure out what it is. I really don't want to end up on the side of the road because of it! Mine has one fuel filter too, in the rear near the fuel pump. I also have a vapor separator in the engine compartment. Replaced the fuel filter about 5K miles ago. Thanks for your help.

Bill

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1987 STD 4WD Hatchback
EA-81 w/hydraulic lifters
Single Range 4WD
133,000 miles

#5 Skip

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Posted 27 December 2003 - 06:08 PM

Not to offend anyone, but he "stupid" vapor separator above the master cyl is another fuel filter.
This is called a "liquid diverter" in some parts stores.
I cut one in half and it is a filter.
Bill, it may be worth a look but
for the problem under load, the power valve in the bottom of the fuel bowl could be to blame as it's function is to supplement the primary throttle bore under low vacuum (high load) conditions.
Might try some "Sea Foam", a miracle in a can available at NAPA and Advanced Auto Parts houses, that has been known to well work miracles.


#6 4FOR4

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Posted 27 December 2003 - 06:24 PM

I'm having the same trouble wit the '86 BRAT, started about a week ago and is getting progressively worse. I'm going to try the fuel filters tomrrow.

Seems to happen when under load, usually at about 3,000 rpm in third and fourth gears.

Thought it might be wires but I sprayed the hill out of them and it didn't cause any problems.

How do you check for fuel pump problem? Do you have to drop the tank to change it?

#7 Stupidru

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Posted 27 December 2003 - 09:52 PM

I seen a thread about this a couple years ago, did you get your replacement vapor seperator from SOA? Mine hesitates under load as well...also bogs on deceleration....but mine is ea81t. Thanks Der Skipper & Mr Bill (watch out for Mr. Slugo)

#8 Skip

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Posted 28 December 2003 - 11:58 AM

Mr. 4FOR4, your Brat has a two fuel filters. As outlined in this thread, many times one is neglected. One of my Brats was doing exactly as you mentioned, I found the rear filter almost plugged. The Brats, as all Subarus of this vintage, has an external to the tank fuel pump. Kneel down by the rear of the drivers door and look under the cab. A small shelf with the fuel pump is there. The input line to the pump has the primary fuel filter. This filter is often overlooked.
As for testing the pump, please ask in a separate post or email me directly.


Sir Stupidru, I see your other post working. The fuel filter on the turbo vehicle is a horse of a MUCH different color. There is only one, located under the hood in the area above the master cyl. PLEASE make sure you get a turbo fuel filter, catastrophic results may happen if a carbed fuel filter is used.
As evidenced in a turbo car Noah, Steve and I saw in a boneyard.
Steve was going to show a picture of this engine.
It was a shot of the carbed fuel filer - it burst under the FI fuel pressure and torched the entire under hood area.


#9 Setright

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Posted 28 December 2003 - 02:34 PM

Well, to me it sounds like plug wires. Intermittent, rough running, these two make me suspect the wires. Maybe, but not high on the list: the plugs themselves.

Of course, I am not ruling out a fuel filter.

#10 4FOR4

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Posted 29 December 2003 - 10:48 AM

Spent Sunday afternoon in and under the Brat.

- Changed fuel filter by pump; no better. They didn't have the under the hood one.

- Bought some Sea Foam and did some carb cleaning.

-Dumped some carb cleaner and isopropyl in the gas tank.

- Filled it with 93 octane.

The dropping out / rough run problem moved to 4,500- 5,000 rpm. You really have to push it in 3rd to get to happen but it still does.

What's the concensus? Carb or fuel pump? At what point should you see fuel spraying through the rear (smaller) jet of the carb? While revving I can see the front but never the back, or the throttle below it move. What's its purpose, high load?

#11 Stupidru

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Posted 29 December 2003 - 10:53 AM

I'm almost to the bottom of the tank & mine is disappearing as well. I think I got a bad batch of fuel.

#12 Stupidru

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Posted 30 December 2003 - 09:43 AM

Filled-up w/ 87 hesitation is gone.

#13 sidekickin

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Posted 01 January 2004 - 06:10 AM

Went ahead and replaced both fuel filters again a few days ago. Tonight when going 65 mph up a slight grade, the car started sputtering and running rough again....acts just as if the car is running out of gas. Only does it intermittently when under a load. Some nights it will act up and some nights it will be fine. Car has plenty of gas in it at all times. Any other suggestions? Thanks!

Bill

______
1987 STD 4WD Hatchback
EA-81 w/hydraulic lifters
Single Range 4WD
Hitachi 2BBL carburetor
133,000 miles

#14 beauregaardhooligan

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Posted 01 January 2004 - 08:45 AM

A weak spark can make for sputtering under load. Does it smoke when it sputters? If you let up quickly when it sputters, does it backfire?
Put some new NGKs in it.
I'm still leaning toward dirty carbs.
Try a hillbilly tune-up, revving the motor with your hand on the venturi.
Use your favorite gas treatment and a fresh tank of gas.
Skip, isn't the under-the-hood gas filter called a *water* vapor separtor?

#15 Stupidru

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Posted 01 January 2004 - 11:39 AM

Try dry gas & 87 octane. This time of year, 89 & 93 collect condensation in pump tanks cause there not used as frequently as 87. Hesitation on hills also indicates clogged catalyst.

#16 Skip

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Posted 01 January 2004 - 02:22 PM

Ed, to the best of my knowledge it is simply called a "vapor separator"
I believe it is situated high in the engine compartment so that any vapor forming in the fuel line will rise into it and be diverted back to the fuel tank rather than form a "vapor lock"
As I said, I have had it called a liquid diverter at a NAPA store, again diverting the liquid gas into the carb and the gas vapors back to the tank.


#17 4FOR4

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Posted 01 January 2004 - 06:20 PM

[QUOTE]Originally posted by sidekickin
[B]Went ahead and replaced both fuel filters again a few days ago. Tonight when going 65 mph up a slight grade, the car started sputtering and running rough again....acts just as if the car is running out of gas. Only does it intermittently when under a load. Some nights it will act up and some nights it will be fine. Car has plenty of gas in it at all times. Any other suggestions? Thanks!

Bill

I'm still having same trouble with Brat and it seems that going up hill makes it happen. Any body know why going up hill, other than increased load, would matter?

#18 beauregaardhooligan

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Posted 01 January 2004 - 06:49 PM

Incorrect float level?
I checked in the '83 FSM.
Chapter 4-10, page 4-36, section 2;
"Inspection
1) Inspect vapor separator if the foreign matter exsists in it. Replace it if it will interfere with running.
{Gotta love these stilted translations!}
2) If water is found in it, shake it with its outlet downward, and water will be removed."
There is a return line to the tank, so I'm guessing it will separate gas and/or water vapor.
In any case, it needs to be changed regularily.

#19 4FOR4

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Posted 06 January 2004 - 10:46 AM

Thanks to all that helped. It ended up being the part with many names:

2nd fuel filter
vapor separator
liquid separator
liquid diverter

It's the 3 port fuel filter lookin thing on the fire wall above brake master cylinder.

On the way to the parts store it would start to sputter at about 4,500 rpm.

Changed it in the parking lot and on the way home I could red line (almost, 5,500) it and it took it like a Brat (Not that I condone going 70 in 3rd, but it was in the name of science).

Another example of how regular maintenance is the key to happy motoring.

#20 Sweet82

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Posted 06 January 2004 - 11:00 AM

I've had these problems over the years........

I found a basic tune up will cure 99% of everything. Wires, Cap, Rotor....

Being winter, I'd also try a bit of fuel line treatment to get any water out of the system.

My .02

Glenn,
82 Hatch, well it started out that way......
01 Forester, bent but not broken...........

#21 Stupidru

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Posted 06 January 2004 - 02:56 PM

4for4...what did you ask for at auto parts store or was it on the shelf. My vapor seperator is a tiny metal cylinder (almost like a miniture version of my fuel pressure regulator) & mine is in-line before the fuel pump. Never seen anything like it on the shelf.

#22 4FOR4

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Posted 06 January 2004 - 03:12 PM

I think I was calling it a vapor separator.

Carquest And NAPA had no listing for the thing.

Advanced Auto Parts has a pretty good computer set up.
We looked under fuel filters and it listed a half dozen or so various brands. One of the listings was labeled '3 port'.

The guy clicked on that and it was the beast I was looking for. Two 5/16" ports at the bottom coming off in a peace sign, a 1/4"port at the top, which I assume is the vapor return line back to the tank, but I'm not sure about that. Had to wait for it to be shipped from main warehouse, the showed 3, only 3.

It's made of white, somewhat see through plastic, located where I described earlier under the hood.

The 'other' fuel filter on the Brat (I have '85 and '86, both the same setup) is located down by the fuel pump under car behind driver door. It looks like the one under the hood but no 1/4" port on top.

Both CarQuest and Napa, after checking their computers will give you a fuel filter with ports coming out in two directions instead of the V or peace sign arrangement. Doesn't fit real well in the holder under the BRAT but it works OK.

#23 Stupidru

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Posted 06 January 2004 - 03:20 PM

thanks 4for4!




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