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unsteady idle


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25 replies to this topic

#1 brokebill

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Posted 07 March 2008 - 05:29 PM

my carbed 86 GL wagon fluctuates 200-300 rpm when idling.
it went away last week for a couple days and had never ran smoother. couldn't even tell it was running when at a red light.
now its back. runs out fine but idles poorly again.
dont know why it left or why it returned.

has pretty much idled this way the whole time i've had it (about 3 yrs)and if it hadn't cleared up for a couple days wouldn't have thought anything about it.
after knowing how smooth it can run, would like to get it that way for good.

i know theres a million things that can cause this but would appreciate some advice on the most likely culprit.

it has fairly new plugs, wires and fuel filter and it didn't clear up after doing anything particular to it. just cleared up on his own and went back to its old ways on its own.

thanks, Bill
-----------------
forgot to add, i have sprayed around with carb cleaner looking for vac. leaks. no luck, and used some seafoam deep creep today in the carb.
didn't smoke very much after i used it and sadly it didn't seem to help.

#2 Quidam

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Posted 07 March 2008 - 10:16 PM

You are due for a complete carb rebuild and or replacement. If you haven't gained access to the idle mixture screw, start there.

#3 brokebill

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Posted 07 March 2008 - 11:13 PM

through receipts i found in it when i got it, a carb had just been put on. dont know if it was junkyard, old rebuilt ,or how competent the people who did the work were.

when i had a timing belt put on last year by a garage (ive since replaced belts , idler pulley,tension adjusters myself, thats how i found usmb) i know for fact they messed with the mixture screw thinking it was the idle adjusting screw.

how would i go about adjusting mixture screw without making things worse since thats a real possible cause of my problem?

thanks, Bill

#4 brokebill

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Posted 08 March 2008 - 10:34 AM

from the threads i've found on the subject usually the mixture screw is covered by a plug or something but mine is not.
its a recessed screw completely visible on the front of carb just below the idle adjuster screw. correct?
i know it should be left alone but they started it so i guess i have to finish it.

also, should my idle adjusting screw have a little up and down play in it?
idle responds correctly (faster or slower) when turning the screw,but with the tip of the screwdriver i can feel and see a little up and down, side to side play.

thanks, Bill

#5 Quidam

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Posted 08 March 2008 - 11:25 AM

from the threads i've found on the subject usually the mixture screw is covered by a plug or something but mine is not.
its a recessed screw completely visible on the front of carb just below the idle adjuster screw. correct?
i know it should be left alone but they started it so i guess i have to finish it.

The plug has been removed from the "Protector". Good. Here's what I would do: Remove the idle mixture screw. Remove the protector, that aluminum piece the screw goes through. Retrive the spring inside the protector. Put the spring on the idle mixture screw, put it back in the carb until it's fully seated, being careful not to tighten it down when it's seated. Turn it out two turns. Start the car, with it warm adjust the mixture screw.

Spray the mixture screw like you're checking for a vacume leak. Blue loctite on the mixture screw threads will seal it if you have a leak there. Check for vacume leaks on the throttle shaft, both sides of the carb.

also, should my idle adjusting screw have a little up and down play in it?
idle responds correctly (faster or slower) when turning the screw,but with the tip of the screwdriver i can feel and see a little up and down, side to side play.

thanks, Bill


That's normal movement on the idle screw, at this point in its life.

Doug

#6 Gloyale

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Posted 08 March 2008 - 11:58 AM

I'll bet the culprit is the Air Injection Vaccum Valve. Near the Thermostat housing. It develope leaks and stops functioning propperly, cauing rough idle. I remove it on most carbed Vehichle I work on. Ussually helps steady the idle quite a bit.
Posted Image
This picture shows it and it's 2 skinny vacuum lines. There are 2 larger lines not shown, that hook to the top of the carb. Plug both of the 2 larger ports on the carb, and the 2 lines shown here, and remove that thing.

#7 Quidam

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Posted 08 March 2008 - 12:34 PM

Before.

I'll bet the culprit is the Air Injection Vaccum Valve. Near the Thermostat housing. It develope leaks and stops functioning propperly, cauing rough idle. I remove it on most carbed Vehichle I work on. Ussually helps steady the idle quite a bit.
Posted Image
This picture shows it and it's 2 skinny vacuum lines. There are 2 larger lines not shown, that hook to the top of the carb. Plug both of the 2 larger ports on the carb, and the 2 lines shown here, and remove that thing.


After
Posted Image

#8 brokebill

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Posted 08 March 2008 - 04:19 PM

i think it Posted Imagemay already be gone cause i sure don't see it.
could that be what the "mystery" hose to the right of the pic once attached to?

overlook my pic posting ability, i have an odd setup & still learning.

#9 brokebill

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Posted 08 March 2008 - 05:29 PM

Posted Image

i'm trying.
thanks, Bill

#10 Gloyale

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Posted 08 March 2008 - 09:45 PM

Well, crap, you have a feedback carb. that explains some of it.

You didn't have that thing to begin with.

YOu could try to diagno using the ECU.

Do you have a CEL? Any codes on the LED?

Connect the test connectors and see if you get any.

#11 GeneralDisorder

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Posted 08 March 2008 - 09:52 PM

This picture shows it and it's 2 skinny vacuum lines. There are 2 larger lines not shown, that hook to the top of the carb. Plug both of the 2 larger ports on the carb, and the 2 lines shown here, and remove that thing.


You don't want to plug the ports on the carb - those are supposed to be open to the air cleaner via the air control vacuum valve. They are the air supply that regulates the mixture. Without those ports open, the carb will run rich as it thinks the engine bay temp is below the opening temp of the thermo-vacuum valve (EA81) or solenoid valve (EA82) that opens it.

.....I'm not entirely sure if that valve is supposed to be open, or closed, or what - how it regulates airflow through the metering ports is something I have not as yet tested. What I can tell you is that it's supposed to have vacuum above 81 degrees F engine bay temp (EA81) or through some other magic mind reading all knowing oracle type device on the EA82's. I would not be tossing it in the crapper till I knew the proper airflow to the metering ports though - and plugging them is probably not the answer.

On a feedback carb, those same ports are used to regulate mixture via the duty solenoid(s). But in the case of the feedback's, the jetting is different and the duty solenoids meter the air to bring the mixture within spec as judged by the ECU.

GD

#12 GeneralDisorder

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Posted 08 March 2008 - 10:04 PM

Also - to partially answer the original question.

1. You have a feedback EA82 Hitachi. Bad juju in the worst way. Not only is it the EA82 Hitachi with the poorly designed choke spring, but it's jetted in such a way that it can't be run properly without the duty solenoids, and the ECU+sensors are a mess that really is cost prohibitive to repair.

2. There's stuff in there that doesn't work, and at this point never will again. The price of the manifold pressure sensor at the dealer is so outragous as to be silly.

3. Tuning it properly is a nightmare and a half. You actually need a tail-pipe sniffer according to the FSM to properly adjust the duty solenoids, etc.

4. Your carb is probably wore out as well - rebuilding it is possible, but since the rest of the stuff doesn't work properly.... what would that gain you?

Dump the whole mess in the crapper and put on a Weber or SPFI. It's the only proper cure for the EA82 feedback. The EA81 system isn't quite as bad, but most people can't work with it either.

Dump it.

GD

#13 brokebill

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Posted 08 March 2008 - 10:16 PM

so to try and sum it up in my mind;

1- the original carb was replaced with a troublesome thing?

2- be glad it runs out as good as it does?

3- if and when it craps out replace it with one of the forementioned carbs?

is that about right?

thanks, Bill

#14 Gloyale

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Posted 08 March 2008 - 10:37 PM

those are supposed to be open to the air cleaner via the air control vacuum valve. They are the air supply that regulates the mixture. Without those ports open, the carb will run rich as it thinks the engine bay temp is below the opening temp of the thermo-vacuum valve (EA81) or solenoid valve (EA82) that opens it.


True true. They are the slow air control and main air control. I should have said bypassed with a *T* fitting, connected to the air cleaner. Like this.

Posted Image

#15 GeneralDisorder

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Posted 09 March 2008 - 01:50 AM

so to try and sum it up in my mind;

1- the original carb was replaced with a troublesome thing?


Nope - the feedback Hitachi is orignal.

2- be glad it runs out as good as it does?


I suppose - if it were me I would be doing an SPFI swap - easy on the EA82's.


3- if and when it craps out replace it with one of the forementioned carbs?


Weber of SPFI, yeah.

GD

#16 brokebill

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Posted 09 March 2008 - 02:27 AM


I suppose - if it were me I would be doing an SPFI swap - easy on the EA82's.

GD


since it runs out well and doesn't idle that bad(when set at 1000-1200 rpm cant even notice it) not enough of an issue to swap yet.
Good to know when the time comes though what i need to do.

been reading up on the feedback carbs and you sure are right about all the crap on them. ridiculous piece of engineering!

couple questions,
why does it even have the idle mixture screw with all the systems built in mixture adjusting crap?
and
since i'm at a fairly high altitude could the HAC system be playing a role in the slightly rough idle or is mine probably not equipted with that?

thanks for the tips, Bill

#17 brokebill

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Posted 09 March 2008 - 02:05 PM

just a quick update, checked for codes today and it only showed the 11 code for the make and model.

can't find anything that looks like it is or could have been the HAC so thats probably not it.

still wondering about the fuel mix screw since i know its been messed with but afraid i may just make it worse if i fool with it.

thanks, Bill

#18 brokebill

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Posted 23 March 2008 - 06:57 PM

little different problem, but all my carb info is on this thread so here goes,

got the idle straightened out, ended up working the egr valve up and down a few time and smoothed him right out.

pulled out in traffic today and had to get in the gas pretty hard. started bogging down and running rough.

once i'm moving and stomp the gas , it will go pretty good.
pulling out and light acceleration its awful.

has done this a couple times months ago when i got in it hard pulling out but the car wasnt warmed up good and went away after a few seconds when it did it before.

had to drive about 20 min. to get home today and it didnt clear up.

pulled a couple plugs and looks like it was running lean on the way home.

this car puts food on the table , so,
Help!
thanks, Bill

#19 Durania

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Posted 23 March 2008 - 07:48 PM

Just to throw this out there. Have you checked your intake manifold gaskets? They cause some crazy motor issues when they go out.

#20 brokebill

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Posted 23 March 2008 - 10:16 PM

i've been outside the last few hours and have set the timing to make sure it is ok

sprayed everything under the hood with carb cleaner looking for a vac leak

sprayed every moving part and wire or connector with wd40
deepcreep seafoamed the carb. lotsa smoke , but no help.

has been running the best he ever has lately and just did this out of the blue.

idling perfect , but as soon as i touch the gas , it tries to die unless i nurse it then stomp it.

thanks, Bill

#21 hatchsub

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Posted 23 March 2008 - 10:47 PM

Sounds like classic Accerator pump problems. thats in the carb and its what shoots the gas into the carb when u step on it initially from a stop.

#22 GeneralDisorder

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Posted 23 March 2008 - 10:54 PM

You can't find all vacuum leaks with carb cleaner. That will only find the most obvious ones.

Your problem is related to the transision between the idle circuit and the main circuit it sounds like. This is either a poorly adjusted idle mixture, clogged transition ports, clogged main circuit/air bleeds, or vacuum leaks. Or a combination of those.

Start disabling vacuum supply lines like those that actuate the EGR and the choke pull-off systems. It could be a leaky hose, but it could also be a leaky vacuum device. I noticed a big improvement in disabling both the vacuum choke pull-off and the thermo-vacuum valve that supplies the air to the vacuum valves for the air mixture metering ports. You don' need either - just route vacuum to the metering port vacuum valve irregardless of the state of the thermo-valve. Or you could eliminate the vacuum valve entirely and just run the metering ports open to filtered air - make sure you T them together and run them to the air cleaner though or you run the risk of something being sucked into the carb.

GD

#23 GeneralDisorder

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Posted 23 March 2008 - 10:57 PM

Sounds like classic Accerator pump problems. thats in the carb and its what shoots the gas into the carb when u step on it initially from a stop.


For the reccord, I have yet to see a bad accelerator pump on these Hitachi carbs. They have their problems, but that doesn't seem to be one of them. It's possible though - look down the throat and you should see fuel squirt into the primary barrel if you actuate the throttle linkage by hand. Hold the choke plate open if you need to in order to see.

GD

#24 Subaru_dude

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Posted 24 March 2008 - 02:47 AM

I have a non-feedback carb and a Weber. The Weber needs to be rejetted, cleaned up but I don't have the adapter for it. The Hitachi ran OK. I'm only an hour and a half away from you so maybe I could be of some help despite my lack of knowledge when it comes to carbs. There's a pull-a-part in Knoxville with plenty of EA82s so you could get a SPFI setup there.

#25 brokebill

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Posted 24 March 2008 - 02:15 PM

thanks everyone.

started it up this morning, let it fast idle till warm,
and then mashed down on the gas pedal expecting it to bog down.

but instead it ran great, like nothing was ever wrong.

could it have been air/vapor locked?
maybe a piece of something in the carb?

thanks again and appeciate the feedback.
Bill




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