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Tach jumpy all of a sudden...


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17 replies to this topic

#1 gmcfan

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Posted 20 January 2004 - 01:56 PM

1984 ea81 GL Sedan

I was going down to the store last night, 25 degrees outside. The car was fine when I went down there. But, as I drove back, the tach started jumping around from 2000 all the way up to 4000 RPM, sometimes stopping at 4000, then going back down and jittering. I pushed in the clutch and revved it up a couple of times, the tach settled back down, smooth as its always been. Then, a little while later, it started doing it again!

what is the problem, I have read on the repair manual section, that this is caused by a bad distributor, I don't believe it would just start doing it out of the blue. This is the first time it has happened. Could there be something else wrong? anyone else have expereince with this? I don't have the money to get a new or used distributor right now, and things keep going wrong with this thing. It is also my vehicle for going back and fourth to work in. What can I do?

#2 Subarutex

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Posted 20 January 2004 - 03:16 PM

I would guess coil, or dirty contacts on the disty. Take the cap off, and clean the points.

#3 Sweet82

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Posted 20 January 2004 - 03:30 PM

My Hatch does this ocasionally.......

Done it for quite sometime.....

Never fixed it......

Mudrat picked up a spare Junkyard disty here for $12.

I figure when mine becomes a problem, I'll do the same.

Glenn,
82 Hatch, frozen in the garage....
01 Forester, bent but not broken.

#4 NV Zeno

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Posted 20 January 2004 - 03:39 PM

Yeah, my '83 does that, mostly when it's around freezing or below. It hasn't affected performance, so I just list it as one of the many quirks of a 20 year old car that's seen nearly 300,000 miles.

#5 Scoobydoo

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Posted 11 February 2004 - 03:13 AM

ahh, the classic jittery tach.
What's happening (I'm betting) is that the lower spinning bits in the distributor are occasionally hitting the sides of the distributor body. How does this happen? Glad you asked!
The distributor shaft has some flutes machined into it that draw a small amount of oil up to where the distributor shaft rests the distributor body. Unfortunately the shaft does not ride on bearings, but just sits on thin washers. Anyway, the flutes can get clogged, eliminating any lubrication of the washers, and the distributor shaft assembly eventually wears it's way lower and lower in the housing, eventually hitting the sides of the housing (why this makes the tach jump, I don't know, but it does).

You can get a set of "distributor thrust washers" from a Subaru dealership for a few bucks and add them to the stack to raise the shaft assembly (add some grease while you're there). You'll have to tweak the timing a bit too. If not fixed it will get worse, but at a very slow rate. I drove mine for six or seven years with a jumping tach.
If you get a distributor assembly from a wrecker, you'd be wise to take the lower gear off, remove the shaft, and make sure the lubrication flutes are clean.

#6 The Scooby

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Posted 11 February 2004 - 03:47 AM

scooby, thanks for the very informative information, i got the same problem, it was there since i bought my scooby about a month and a half ago, i dont really watch it while im driving, i go by sound and feel. but im gettin another dizzy soon for free.

#7 GeneralDisorder

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Posted 11 February 2004 - 03:51 AM

The shaft of the disty needs to be rebushed..... is this a 2WD or a 4WD? The 2WD disty is made by nippondenso, and these wear out much faster. Well - not really, actually they wear at about the same rate, but the ND mechanicals can't stand nearly as much wear as the Hitachi internals. The problem comes from the variation in the air gap of the rotor inside the disty. The Hitachi design can withstand a LOT of play. I've seen some that were so bad you could move the shaft side to side about 1/8"! The ND will exhibit rapid decay, and almost no noticeable shaft play. Mine went bad in the space of 1 week. It went from perfect, to jumping to 7000 RPM at idle, with a very loud buzzing noise comming from the disty itself (you could actually feel it). It was my only car at the time, and after checking into many options, I found a local shop that will rebush any disty for $35. Their site is here:

www.philbingroup.com

Thet did an awesome job for me - 24 hour turn around.

Just pop the cap off your disty, and try to move the shaft - if you notice ANY (and I do mean ANY) play on a ND, then it's shot. I was very sceptical when I first took my disty apart to look, as the play was hardly noticeable, but it was there. When I got it back from the shop, it was solid as a rock - no play AT ALL.

Almost 100% positive this is your problem - the disty is the only thing on your car that can cause this. A bad coil won't do this - as the tach signal (and what fires the coil), has to come from the disty.

The cheapest I found rebuilt distys, was from roobuilders in Denver - $145 for a complete Hitachi setup.... not cheap. Especially when I just needed a $35 rebush.

GD

#8 Scoobydoo

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Posted 11 February 2004 - 04:08 AM

Good tip, GD. A rebushing is the best solution.
I should add to my earlier comments that adding more thrust washers won't help with the side to side play, but like GD says you can get away with a lot of slop on a Hitachi distributor. When you have it out just spin it by hand and make sure nothing hits (I forget the proper terms, but the star shaped piece just under the rotor will often collide with the, uh, 'prongs' that it spins between. You can bend the prongs out a bit so they clear. Not a perfect solution, but it'll probably get you around.)

#9 GeneralDisorder

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Posted 11 February 2004 - 04:11 AM

I've never seen one with this "washer" problem you speak of scooby.... maybe that's an EA82 thing? I've seen MANY bad EA81 distys, but all were bad from bushings - lots of side play, but never one that hit anything.... curious

GD

#10 Qman

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Posted 11 February 2004 - 11:58 AM

Do the repair, DO NOT BEND THE TABS!!

The air gap is critical to performance. Fix the one you have or get a suitable used one.

#11 Scoobydoo

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Posted 11 February 2004 - 03:15 PM

Actually, it was an EA81 engine that the shaft was boring it's way down into the body. The aluminum body was worn away at the bottom, and even the plastic on hall sensor that circles the shaft had been worn down a bit. It looked like it dropped maybe 2-3mm over the years. At the time, I looked around a lot for a replacement, but could only find ones from the dealership with prices to match. Maybe the distributor was slightly different on canadian models?
I was hesitant to mess with the air gap, but considering the shaft was already flopping around so much I figured I might as well. It performed adaquately that way for awhile until I was able to find a replacement.
Like Qman says, get a replacement. My car was a beater, so "performance" just meant "running."

#12 gmcfan

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Posted 11 February 2004 - 03:45 PM

I checked the disty, about 1/8" side to side play. THanks for the advice everybody, I think I will get it rebushed.

#13 edrach

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Posted 11 February 2004 - 09:25 PM

Ship it to Portland. Best price on a rebuild you can get.

http://www.philbingr...istributors.htm

#14 Russ Hill

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Posted 12 February 2004 - 11:32 AM

Hey,
You guys saved me from having to search for the old post! Cool!
The disty on the new hatch is TOAST.

#15 ebarb

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Posted 26 February 2014 - 05:34 PM

I know this is kind of an old one, but I came across this last night. I've got a Hitachi distributor and have about 1/8inch or slightly more vertical play in the shaft, but no side to side movement that I notice. The stator has slightly more gap on one side of the reluctor than on the other.  I tore down the whole thing to regrease it all as well as replace the vacuum controller. It looked like it had chewed through something and had a thin strip of round metal lodged in the bottom of the distributor kind of near the pick-up coil plate. Almost like it had chewed through a bit of one of these washers. When one of you says thrust washer and the other says bushing are you guys talking about the same thing? Or is there a sleeved bushing that would fit over the shaft and slide down into the housing to hold the shaft in place? Either way I think I need to add a couple more thrust washers/bushings to eliminate the up/down play. 

 

HitachiDistributor.gif



#16 ebarb

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Posted 26 February 2014 - 06:23 PM

The thrust washer set is Subaru P/N: 491867401. Was hoping maybe the local dealership still had access to them, but of course they are discontinued. I hit up Regis Philbin there in Portland and they have do have them. I can't imagine it'll be more than a few bucks. 



#17 ebarb

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Posted 13 March 2014 - 11:08 AM

Ok so I found the bushing you guys were talking about. Mine was definitely worn. I had a spare one so I popped it out and put it in along with a new washer set. Here's a few pics of the pieces for anyone that might run into this in the future.

 

Bushings. Mine was so worn when I looked at the housing I couldn't tell there was anything on top. After looking at another one though it stood up quite a bit further from the housing. 

hitachi-bushings.jpg

 

The new bushing definitely fit a lot tighter than the old one. 

hitachi-distributor-bushing.jpg

 

And the thrust washer set that the diagram depicts.

hitachi-distributor-thrust-washer-set.jp

 

Unfortunately though none of this solved my jumpy tach, but it does seem to have helped with the intermittent miss that I was having. 



#18 coxy

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Posted 16 March 2014 - 04:30 AM

Probably the lube in the tach itself is getting old and thick that is why it more than likely plays up when it gets colder, more common issue than people realise I have a mate that is a trained Scientific Instrument maker who has been an Auto, Marine and specialist Instrument repairer for thirty years including Artillery laying instruments and he says that scenario is quite common on older instruments.






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