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Abnormally high hot idle (Hitachied EA-81) -- any ideas?


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11 replies to this topic

#1 Ma-fia

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Posted 22 March 2004 - 09:59 AM

My 1982 GLF has developed a high idle problem. It starts good and cold idle seems fairly normal to me (1200-1500), but after it starts warming up, the idle instead of slowly going down, is slowly climbing up, to about 2500-3000 rmps.

I am going to dig into the troubleshooting section of the FSM, but I'd like to see if you folks have any ideas.

Before, I was blaming the abnormal idle on the leak in the intake manifold, but the manifold is (finally) back on the car with new gaskets, new original bolts and torqued to the spec, but the problem persists. I marked all the hoses well before taking the manifold off, so there shouldn't be a mix-up there.
The only changes from "before" are cleaned orifice (in the eng.block) and metal pipe going from the block to the EGR valve (both were clogged dead).

#2 subusolo2nut

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Posted 22 March 2004 - 10:08 AM

Might sound simple---but check & see if the choke is getting power. If not, it will open part -way causing elevated idle speed & poor fuel mileage. I have also seen the bi-metal inside the choke go "bad" & cause this:)

#3 GLCraig

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Posted 22 March 2004 - 10:09 AM

From ever subaru I've either owned, worked on or new the owner of; what you are describing is normal. When the rpms start to clime just tap the gas pedal once. The choke then should open to half-way and continue opening untill the engine is warmed up all the way.

#4 Ma-fia

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Posted 22 March 2004 - 10:53 AM

I forgot to mention that the car has a rebuilt carb put on it about 2 years ago.

Tapping (or even stomping) the gas does not render any results -- the idle only goes a notch higher. It would be too nice if this could be solved by adjusting the throttle cable, but I doubt it would help -- the car started doing it on her own accord, it sat for a while, yes, but nobody messed with throttle, vacuums or carb.

I hope it's not the carb, not again!
I will crank her up right now without the airbox and see what the choke plate is doing during all that.

Also, isn't 13-16 ft-lb of torque kinda low? But that's what both books I have say. We tightened it to 20 though -- 16 sounded way too loose! My torque wrench has never been calibrated.
Would it hurt anything if the torque is a bit off?

UPDATE: On cold, I tapped gas once -- the choke closed. I started her and idle was very irregular at first then I tapped gas, it straightened a bit and went to 1500 rpms, but still sounded like the firing was very irregular. Then the same thing - it went up to 2500. At that point the choke was half-way open. I opened it all the way, idle went down to 1500, but still irregular. I guess I need to try cleaning the choke and see if I can adjust hot idle if it opens/closes OK after that.
I hope we didn't fill the engine with crud while replacing the manifold gaskets. I also have a big exhaust leak around rear crossmember.

#5 Ma-fia

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Posted 22 March 2004 - 10:59 AM

Subusolo2nut, are you sure Hitachi choke on EA-81 is electric? I always thought it was mechanical.

#6 subusolo2nut

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Posted 22 March 2004 - 10:11 PM

Well--A '82 could be either one--depends on the emissions package (calif or 49-state) & the month of manufacture--I've seen both with no rhyme or reason in '81 thru '83--guess it was what Subie wanted that week? In any case--the descriptive seemed to fit a electric choke prob--still worth a check-out. :)

#7 GeneralDisorder

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Posted 22 March 2004 - 10:17 PM

Should be electric in my experience.

Simple to check - run it till it's hot, and then open the air filter box - if the choke plate is open all the way, then it's working.

My vote goes next to "carb rebuild" time. Pop the top off the carb, blow out the passages with compressed air, spray liberally with carb cleaner both inside and outside of the carb - put the top back with a new gasket. Should do the trick.

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#8 subusolo2nut

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Posted 22 March 2004 - 10:20 PM

re-read your post---if it was mechanical(only)--you would have a choke knob on the dash on one side of the steering wheel or another--electric choke heats a bi-metal inside the housing--take a test-light & check for power at the wire on the choke cap--if there is power--you might have a bad bi-metal--if no power, you could bypass from the coil + lead to the choke cap (remember to cut the wire from the cap first--your could backfeed the system if not cut) --E me back (see my bio) :)

#9 subusolo2nut

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Posted 22 March 2004 - 10:30 PM

hummm- a GLF--I'm doing a extreme mod to a '82 GLF--re-drilled all the hubs to a 4 on 120mm bolt pattern so I can use 15"wheels with 195/45VR15 Kumo supra tires--lowered the car 3"--re-wound the front springs & re-indexed the rear torsion bars--3" flares with a front air dam--etc-etc-etc. will have pics soon--going to call it my T Rex Wrx--have the 1800 & changing the intake to accept a 40mm Delorto--thought it'd be a fun solo car without spending a ton of cash--:)

#10 Ma-fia

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Posted 26 March 2004 - 03:46 PM

For unknown reason I don't get e-mail notification about replies any more, so I didn't have a clue anybody else answered...

Anyway, the choke plate was the first thing I personally checked with the airbox open.
Tap gas before starting -- it closes like it should.
Warm-up -- it's opening. The car sat for a good while, so first couple of starts the choke didn't want to open 100% (only 90%), but now it does open fully.

We also traced all the vacuum lines and found 2 or 3 that were not where they were supposed to be, that fixed rough idling, but it's still idling way too high.

There's barely 5-7K (if that) on the carburetor after we bought it (fully rebuilt), so the carb is the last thing I want to mess with, really.

#11 Subarino85

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Posted 25 January 2011 - 11:11 PM

What was the problem, & how did you resolve it? My '85 Brat is doing the same thing.

#12 jhs2053

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Posted 29 January 2011 - 11:08 AM

I noticed nobody's answered this after several days, so I'll offer one suggestion. Assuming that you've checked the choke to make sure it's opening fully when hot and that the engine runs well except for the fast idle, you may have an anti-dieseling solenoid that's just re-awakened. It's the octagonal part sticking out of the left front of the Hitachi carb with one wire attached. The solenoid normally shuts off the fuel supply through the slow idle passage if it doesn't get current through the wire, meaning that the engine won't idle when the circuit is interrupted. Many shade tree mechanics deal with this by simply turning up the idle screw until the engine idles on the main jet and get acceptable performance (a little less stable idle and some dieseling when you shut the car off). However, if the solenoid starts working again, the hot idle goes up about 1,000 rpm. You might want to check the wiring to the solenoid to make sure there aren't any breaks or funky connections that might have suddenly started working again. If everything looks OK, try turning the idle adjusting screw back a lot (probably about 2-2 1/2 turns) and see what happens. If it solves the problem, don't leave home without a screwdriver until you're sure the solenoid is trustworthy.




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