EA82 Rough idle, runs fine at higher RPMs

[philipmorg]

I have a 1987 GL Wagon 4WD, EA82 1.8L with an idle problem. Here's what I've observed:

• The idle is extremely rough. The tach shows around 250RPM at idle.
  
• The motor runs normally at higher RPMS, and pulls fine on the highway.
  
• The problem started suddenly, about two weeks ago.
  
• When the motor is cold and the choke is engaged, the RPM is much higher than normal. Normally, with a cold motor and choke on, the idle would be around 1500 - 1800 RPM. Now it is 2500 - 3000 RPM.
  
• If I disengage the choke while the motor is cold, it usually dies. After the motor warms up, it idles very rough and slow, but usually does not die.
  
• Hot or cold, the motor starts up normally. No problem with starting.
  
• I paid a local mechanic to check the problem and he found nothing: no bad valves connected to the carb and no vacuum leaks.
  
• I changed the plugs, distributor rotor, and ran 1/2 can of Seafoam through the tank. No improvement.
  

 

Any ideas on what I can do to diagnose and fix this problem? Thanks!

Edited February 17, 2012 by philipmorg
spelling fix

[AKghandi]

We need info on the car. If its fuel injected I'd check the intake pipe if it's leaking it will do that. I'm not to expirienced with the carb'd motors but GD or someone should be able to shed some light on the problem

[philipmorg]

We need info on the car. If its fuel injected I'd check the intake pipe if it's leaking it will do that. I'm not to expirienced with the carb'd motors but GD or someone should be able to shed some light on the problem

 

Thanks for the reply! The motor is carbureted. What other information can I provide to help diagnose this issue?

[ivans imports]

check the anti backfire circut likes to mess up valve and create internal vacum leack

[philipmorg]

Great, I'll check that valve and report back.

 

Thanks!

-P

[MilesFox]

Might i suggest a vacuum leak. Might i suggest the leak is due to a bad intake gasket. It is worth changing them anyway, the operation is relatively easy. The intake comes off as one piece; carb, airbox, rats' nest and all.

[TomRhere]

I would still suspect a vacuum leak, seeing as it's carbed.

Abnormal "high idle" when cold, along with abnormal "low idle" when warm, tends to indicate a vac leak.

 

You can check for vac leaks yourself, no need to pay someone to do so.

 

Buy a can of carb cleaner.

Pop the hood and start engine.

Start spraying the carb cleaner (using the straw) slowly around the engine, follow ALL of the vac hoses.

Change of engine speed indicates a vac leak.

 

Be sure to check the hoses going to the carbon canister, transmition controls (if it's a Push-Button 4WD type, or Auto), heater-A/C vac resevior.

 

Hoses can crack at thier connection(s), and split anywhere along thier length of run. They are 20 some years old now. Sucks getting "Old"...

[Quidam]

"Any ideas on what I can do to diagnose and fix this problem? Thanks! "

 

What they said and/or hook up a vaccum gage and tell us what it's doing.

 

Doug

[MilesFox]

My 86 3door was like this. First i had to replace the intake gaskets for it to run for more than a block. It drove good, and choke worked, but it would stall in traffic at stops, and either idled high or not at all, depending on how i feathered the pedal.

 

Check that the egr valve is working right, as it should be closed at idle. It could be clogged with carbon which pretty much deletes its function.

 

check the vac line that goes to it. I never did test the egr on mine as a ej22 swap happened before i could do that.