Hesitation and loss of power at freeway speeds

[STUBABREW]

Have a 87 Subaru S/W that experiences hesitation at about 40MPH it feels like it's loosing power and then hit the accellerator and the RPMs will jump up to 5 grand and then back to 3 grand and hang out there not giving any more power. I was wondering if it is an octane thing as I had the issue before my Tbelts went out then after was using gas that i normally didn't use and had no issue. On a road trip I put the safeway gas in and it has not performed right since. I filled the tank with higher octane gas from the station i was using and seemed to be better but still is hesitating.

 

It is a carburated engine with 189k

 

Note. I did perform a search but did not find anything that matched my symptoms

[richardstanley]

Change your fuel filter maybe? Could be a million things eh?

[nvexplorer]

There could have been a little too much water in their tanks, so the filters may be clogged. Wouldn't hurt to do them anyway. Carbed cars have 2 right?

[Prospeeder]

sounds almost like the clutch is slipping...really bad, if its not accelerating and RPMs suddenly jump up to 5k and then sit at 3k and not much power. if its a manual, i suppose an automatic could do that too.

[STUBABREW]

I filled the tank with higher octane gas from the station i was using and seemed to be better but still is hesitating.

 

It is a carburated engine with 189k

 

Note. I did perform a search but did not find anything that matched my symptoms

 

It sat while was at work and came out at lunch and took it for a drive and performed great on the little rod trip and the entire way home.

 

This AM i had only a small bout with it when it was cold and then was great.

 

I guess the mid grade "better Gas is what she likes"

 

Idle in The AM ( first start is extreamly low ) and needs a while to warm up.

[Loyale 2.7 Turbo]

sounds almost like the clutch is slipping...really bad, if its not accelerating and RPMs suddenly jump up to 5k and then sit at 3k and not much power. if its a manual, i suppose an automatic could do that too.

 

Yes, I Think so, but There´s a Li´l Chance to be the Carb´s Secondary Stage Vacuum the Cause of the Problem.

Since it is Carbed, the Hitachi carbs got a Vacuum Activated Secondary, that gives Extra Power to the Engine, if it´s Disconnected, the engine will revv up Normally without any Gear shifted -Neutral- but with load, it Don´t.

If that´s so, I Suggest to check the Vacuum Hoses.

Good Luck!

[thealleyboy]

I guess the mid grade "better Gas is what she likes"

Idle in The AM ( first start is extreamly low ) and needs a while to warm up.

 

Which tranny Brew?

I don't think fuel is your problem...

John

[STUBABREW]

Which tranny Brew?

I don't think fuel is your problem...

John

 

it is the 3 speed Auto

 

I am now only having issues in the AM. Seem to run like a top after small bout with the hessitation.

 

I can feel it shift into all gears but it seems to shift into second at 4500 rpm

[thealleyboy]

My guess is the tranny.

If you are winding it up to 4500 RPM and it's not shifting, it's has to be either vacuum-related, or mechanical within the tranny. This may not be as bad as it seems. Sometimes, replacing the modulator or servicing the governeor solves the problem.

I had these symptoms recently, and unfortunately for me, the tranny itself was shot. But it well-worth giving it a try. There is a good write-up on reconditioning the governer gear on this Board.

One other bit of advice: don't run your motor too hard if you feel it losing power on the freeway (isn't shifting up properly). I went up pretty high (5000-5500k), and now the motor is starting to make low end noises. Don't risk trashing your motor over a stupid 3AT.

 

good luck, John

[STUBABREW]

Shop said, the the 2nd barrel was clogged and I have it set lean

 

i have used seafoam in the tank and down the throat. can travel at 55 now befor the hesitation

 

My quetion is if there is a vaccum issue would it affect the 2 barrel from opening properly?

 

at what speed or RPM does the 2 barrel usally open ?

 

 

My guess is the tranny.

If you are winding it up to 4500 RPM and it's not shifting, it's has to be either vacuum-related, or mechanical within the tranny. This may not be as bad as it seems. Sometimes, replacing the modulator or servicing the governeor solves the problem.

I had these symptoms recently, and unfortunately for me, the tranny itself was shot. But it well-worth giving it a try. There is a good write-up on reconditioning the governer gear on this Board.

One other bit of advice: don't run your motor too hard if you feel it losing power on the freeway (isn't shifting up properly). I went up pretty high (5000-5500k), and now the motor is starting to make low end noises. Don't risk trashing your motor over a stupid 3AT.

 

good luck, John

[Frank B]

The secondary venturi opens as the engine load requires it, not really at a certain speed. When you push the throttle down, do you feel a bit of a hard spot about half way? That's the secondary linkage ingaging. It will start to open mechanically about half throttle. When that happens it creates a vacuum signal and if the engine needs it, it will open up. You really need to disassemble the carb to clean it correctly. Use a Subaru rebuid kit if possible, many of the kits you can get at a parts store are crap. If you have the money, buy a reconditioned carb. http://www.nationalcarburetors.com/cat-subaru.html I have one from them on my hatch and it's awesome!!

This may work too,

http://cgi.ebay.com/ebaymotors/Carburetor-1985-1988-Subaru-2-4-Wheel-Drv-1800-Eng_W0QQitemZ170101790248QQihZ007QQcategoryZ33550QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

 

Change the tranny fluid and filter too, I like the Mercon V fluid. Also the front differential gear oil. Replace the vacuum modulator too while your at it.

[STUBABREW]

Thank you all for the input that you have given. I am making slow but sure progress on this issue.

 

The idle seemed to be a bit low (lean) 500 to 700RPM at idle

I raised the idle to 1000 to 1200 and it seems to be a little more responsive.

 

I still get the hesitation but it starts at 55 to 60 mph. If i back out of the gas a bit when it is doing that it seems to get better.

 

My question now is. Is there a Diagram for vacumme hoses to see if they are all going to the appropriate places.

 

Is it still needing a rebuild of the carb as the mechanic said?

[psylosyfer]

This may sound crazy, But have you replaced the rear fuel filter?

My GL acted very much like your's. At first intermittently then always.

For some reason I never suspected the fuel filter, But when I finally got to it

all the symptoms ceased.

Incidently my trouble started after buying gas at a "hole in the wall" in rural Oregon.

NVEXPLORER may be right about water in the fuel.

My rear filter looked like the element was distorted and had a buildup of sediment in it. You could blow through it but not freely.

[psylosyfer]

There could have been a little too much water in their tanks, so the filters may be clogged. Wouldn't hurt to do them anyway. Carbed cars have 2 right?

Yeah one near the fuel pump and one under the hood.

[STUBABREW]

Well had some time to tinker and allthough the shop was convinced that the carb was the issue..... I changed the fuel filter and wala it has power and no hesitation.

 

I changed the filter under the passenger rear back side. I cannot locate the other one in the engine compartment.

 

I am a little confused any help would be greatly appreciated

[Gloyale]

Yeah one near the fuel pump and one under the hood.

 

 

Sometimes people add the little inline filters to the carbed models somewhere near the intake. But from the factory there is only one filter. It's located on the fuel pump bracket near right rear wheel.

 

SPFI and MPFI models use a filter near the left strut tower. They don't have one underneath.