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Constant Speed Roughness


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16 replies to this topic

#1 NV Zeno

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Posted 04 December 2005 - 04:00 PM

'83 EA81 4WD 4MT, Hitachi Carb (California spec):

OK..Over the last few hundred miles, this car has developed an odd problem. When just "goin' down the road" at partial throttle, the engine seems to kind of stumble the whole time, like a constant hesitation. Not any major loss of what little power this car has:rolleyes: , just a mild roughness to the way it runs. In addition, when accelerating, or "going through the gears", the engine seems to accelerate much better (like a sudden turbo boost) at around 3500 RPM, all the way to the time I have to let off and shift.

I recently replaced both fuel filters (that cleared up another prob I had), spark plugs, cap and rotor, all well before this current issue started.

Today I disconnected the vac advance line to see if there would be any difference. Test drove, no change..replaced vac line.

I have guessed there could be two possibilities: shot vac advance, or carb problem of some sort.

Choke works fine, idle is good and smooth (although a couple hundred high), no stalling or rough idle.

Opinions, advice, educated guess?

Thanks

#2 jxavierf

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Posted 04 December 2005 - 04:03 PM

What was the problem you had that was fixed when you installed the new fuel fitlers?

#3 NV Zeno

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Posted 04 December 2005 - 04:08 PM

What was the problem you had that was fixed when you installed the new fuel fitlers?


That was the classic fuel starvation when a high demand for power was needed (any uphill grade, overpass, or strong head wind:lol: )

#4 NorthWet

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Posted 04 December 2005 - 05:07 PM

...I recently replaced both fuel filters (that cleared up another prob I had), spark plugs, cap and rotor, all well before this current issue started...

You mentioned spark plugs, but how about spark wires? And were these spark plugs subjected to the fuel starvation that prompted you to to change the filters?

#5 NV Zeno

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Posted 04 December 2005 - 05:32 PM

You mentioned spark plugs, but how about spark wires? And were these spark plugs subjected to the fuel starvation that prompted you to to change the filters?


Wires are Magnecor, a couple years old..checked for cracks and tightness, all OK. Car does not exhibit the symptoms of a bad plug wire, completely different from that.

Spark plugs were replaced before the filters (filters last week). I removed the plugs a couple of days ago to inspect/clean. There was some black carbon buildup (nothing major) on most of them..cleaned with wire brush, re-gapped, replaced.

No change.

#6 hooziewhatsit

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Posted 04 December 2005 - 07:40 PM

try some seafoam in it yet? Both straight through the carb and in the fuel tank? Worth a shot if nothing else :drunk:

To test the vacuum advance in the disty... take the cap off, unplug the vacuum line, attach a clean vacuum line to the disty, and start sucking (and stop laughing :-P) If the mechanism moves and holds, I think it's safe to say the vacuum advance works.

#7 subieman

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Posted 04 December 2005 - 07:50 PM

Dave, I have the same problem on my 86 ea82 and it's carb related. Maybe your accelerator pump is going out or has an air leak. Or maybe its because your car has 300,000 miles on it! :)

#8 ShawnW

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Posted 05 December 2005 - 07:09 PM

Id say its the accel pump.

#9 TheSubaruJunkie

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Posted 05 December 2005 - 07:59 PM

I'd say its old and needs to be retired. I think i know of a buyer :brow:

-Brian

#10 NV Zeno

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Posted 05 December 2005 - 08:29 PM

Thanks for the replies. I haven't pursued it much in the last couple of days, been too cold (and I've been too lazy:lol: ) and I thought I'd take a break from it for awhile to compile the info you all have provided.

Brian, if you're looking for an EA81 or 82, I'm sure we could find something for you around here easily..only you have to live here to be able to register without smog check (Jeremy's part of Washoe county has smog check, mine does not). Now's your chance to bail out of "Calitreehuggerenvironmentalwackofornia"

Retire my wagon? Why? it's only got 297K, plenty of life left!:grin:

#11 TheSubaruJunkie

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Posted 06 December 2005 - 12:47 AM

297k? Are you rolling back? I thought you were in the 300's by now. I cant move out of calfuquindassfornia till my lease is expired. But you know ive been thinking of it.

I say you slap a weber on there and get alittle more gusto out of your old ea81. Will help you keep up with me on the trails :-p

-Brian

#12 NV Zeno

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Posted 06 December 2005 - 02:11 AM

297k? Are you rolling back? I thought you were in the 300's by now. I cant move out of calfuquindassfornia till my lease is expired. But you know ive been thinking of it.

I say you slap a weber on there and get alittle more gusto out of your old ea81. Will help you keep up with me on the trails :-p

-Brian


Keep up with you on the trails? Heck, I was keeping up with Jibs' lifted BRAT:lol: :lol: !

Film at 11.:-p

#13 joostvdw

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Posted 28 May 2006 - 01:05 PM

has this ever been solved?

because I have a very similar problem, on my MPFI XT turbo :rolleyes: and was hoping someone had a clue..

#14 NV Zeno

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Posted 28 May 2006 - 04:10 PM

has this ever been solved?

because I have a very similar problem, on my MPFI XT turbo :rolleyes: and was hoping someone had a clue..


Not really. I've learned to "adjust" the way I use the throttle and just got used to it. I've asked around, and have been told that it's something that is pretty much a normal occurance. Remember, that carb is almost 25 years old:rolleyes: .

Hope this helps.

#15 GeneralDisorder

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Posted 28 May 2006 - 05:31 PM

(I know - old thread - but you are still having the issue so....)

Probably just a gunked up main jet or venturi in the carb. It's probably not a real clean spray pattern, and you might need a new gasket between the two carb halves - might be sucking air.

Accelerator pump is only used when you are actively pushing down on the pedal. When the pedal is held still it's not used.

Shouldn't be hard to clean it a little - just pop the top off the carb and spray all the passages with compressed air. Replace the top gasket and give it a go. Can also use the redneck trick and hold a rag over it while revved up to suck some of the crap out of the carb.

GD

#16 joostvdw

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Posted 29 May 2006 - 03:53 AM

thanks for the info/help

but I did mention I have a MPFI XT turbo, so no carbs, FI ;)

I still hope someone has any ideas, because it is annoying the hell out of me, it's also a lot more noticeble when it's cold, dunno if that matters, but hey...

#17 Hank Roberts

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Posted 30 May 2006 - 09:04 AM

Sounds exactly like the what my 1988 GL did with a slowly degrading Throttle Position Sensor. I don't know if yours has that item -- it's a solid state device. Once I had mine replaced I was just amazed, I'd been driving the Subaru for a year off and on between repair and replacement vacations, thought I knew how it felt.

I drove it over 300 miles last weekend after the TPS was changed. It was completely different. Smooth, predictable increase and decrease in RPMs with gas pedal motion, instead of the ratchety jerky sometimes delayed response, and far more of a range of motion/RPMs than I had ever known these engines were capable of.

The throttle used to basically offer just 'sputter along, roll along, try to go fast' -- it's now a whole smooth range of motion.

It's the one thing I've gotten fixed on the, well, third try. First try the mechanic didn't believe there could be a problem. Switched mechanics. Second place just "cleaned the TPS" without testing it, didn't believe me. I brought it back and insisted they do the test by the book and it failed completely. They found one from a junkyard and at my insistence they tested that before putting it in, instead of just swapping parts and pretending it was a repair.




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