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#4514434 - 09/12/17 06:00 PM 1985 Olds 88 carburetor question
JimPghPA Offline


Registered: 08/22/09
Posts: 3859
Loc: Pittsburgh,PA U.S.A.
Our 1985 Olds 88 with the 5 liter gas Olds engine and 164,XXX miles is having a problem. It idles way too slow once the engine is completely warmed up. After driving it for 25 minutes the idle is so slow the the oil light is coming on dimly when you completely let off the gas and the engine has to idle when the car is stopped.

Does anyone have any idea about what part of the carburetor adjustment I should be looking at if it is the carburetor?

Thanks in advance for any information.
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#4514438 - 09/12/17 06:04 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
JimPghPA Offline


Registered: 08/22/09
Posts: 3859
Loc: Pittsburgh,PA U.S.A.
PS, the idle speed is OK when the engine is cold, so I do not think it is a simple idle speed adjustment, as increasing the idle via the idle screw makes it idle too fast when it is cold.
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#4514441 - 09/12/17 06:07 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
WobblyElvis Offline


Registered: 09/23/14
Posts: 1343
Loc: Toronto Canada
There are many adjustments on that carburetor, and if you search the net you will find many images/diagrams that will assist you. I assume you have a Rochester 4 barrel. Here is one image that may help but you should identify the carburetor first.
http://repairguide.autozone.com/znetrgs/...15280080ba3.gif


Edited by WobblyElvis (09/12/17 06:08 PM)

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#4514457 - 09/12/17 06:22 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
Chris142 Online   content


Registered: 06/05/03
Posts: 16817
Loc: Deplorable in apple valley, ca
Things don't normally change unless someone messed with it. Usually the idle circuits get dirty. If they have not been drilled out so they can be adjusted now is the time to do so.


Edited by Chris142 (09/12/17 06:23 PM)
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#4514466 - 09/12/17 06:33 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
mk378 Offline


Registered: 09/27/15
Posts: 1414
Loc: USA
There's no control over how much it steps up the idle speed when cold. Instead you adjust the idle speed screw for proper speed when warm, and accept whatever you have when cold.

Make sure the choke heater system is working, so that it goes into warm mode without undue delay.

If car is otherwise running OK I would not touch anything on the carb other than the idle speed.

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#4514474 - 09/12/17 06:45 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
eljefino Offline


Registered: 06/15/03
Posts: 32631
Loc: ME
If there's a solenoid that keeps the throttle propped open at idle check that it works.

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#4514483 - 09/12/17 07:07 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
kc8adu Offline


Registered: 08/02/05
Posts: 894
Loc: dayton oh
time to rebuild the carb.
between heavy floats(get a brass one)leakdown,and worn throttle shafts most need a rebuild before 100k.
there is also a thermal vacuum valve that goes bad and sucks fuel out of the bowl vent.
its the cause of many gross polluter cases with these.
you need a tool to adjust the mcs.
simply count the turns to bottom it and make a note.
when reassembling it run it to bottom and back it out the number of turns you recorded.
and dont forget to jbweld the plugs in the bowl.
they are not that hard to rebuild.

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#4514485 - 09/12/17 07:08 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
bullwinkle Offline


Registered: 10/09/04
Posts: 7659
Loc: Cincinnati, OH, USA
I used to have an '85 5.0/305 with the emission Quadrajet carb, I could only get a year or a little longer out of it before it had the same issue, pretty much had to get another rebuild every time. The gasohol was tearing them up.
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#4514490 - 09/12/17 07:11 PM Re: 1985 Olds 88 carburetor question [Re: eljefino]
kc8adu Offline


Registered: 08/02/05
Posts: 894
Loc: dayton oh
might wind it out a touch to bump idle but its primary purpose is controlling idle when a/c come on.
Originally Posted By: eljefino
If there's a solenoid that keeps the throttle propped open at idle check that it works.

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#4514503 - 09/12/17 07:21 PM Re: 1985 Olds 88 carburetor question [Re: kc8adu]
eljefino Offline


Registered: 06/15/03
Posts: 32631
Loc: ME
Originally Posted By: kc8adu
might wind it out a touch to bump idle but its primary purpose is controlling idle when a/c come on.
Originally Posted By: eljefino
If there's a solenoid that keeps the throttle propped open at idle check that it works.


It depends, there are some that shut off to prevent dieseling when you turn the key off. The holley on my 85 dodge is like this.

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#4514510 - 09/12/17 07:25 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
kc8adu Offline


Registered: 08/02/05
Posts: 894
Loc: dayton oh
the primary adjustment is the stop screw.
but the real fix is a rebuild.

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#4514511 - 09/12/17 07:25 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
user52165 Offline


Registered: 10/21/11
Posts: 1331
Loc: CA
Is this car still required to have smog testing?

If not, consider a new Edelbrock or other carb. Compatibility may be an issue, but check it out.

1985 carbs are burdened with complex, expensive, and difficult to service systems.This was the end of the carb era.

If you can avoid that nightmare, do it


Edited by user52165 (09/12/17 07:31 PM)

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#4514521 - 09/12/17 07:31 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
kc8adu Offline


Registered: 08/02/05
Posts: 894
Loc: dayton oh
and replace the rats nest of vacuum lines.one at a time.
unless you plan to remov/replace every part of the c3 system forget aftermarket carbs.
and while the carb is off clear the egr ports under it.
clogged egr will cause ping at cruise during lean cruise mode.

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#4514535 - 09/12/17 07:43 PM Re: 1985 Olds 88 carburetor question [Re: kc8adu]
user52165 Offline


Registered: 10/21/11
Posts: 1331
Loc: CA
Originally Posted By: kc8adu
and replace the rats nest of vacuum lines.one at a time.
unless you plan to remov/replace every part of the c3 system forget aftermarket carbs.
and while the carb is off clear the egr ports under it.
clogged egr will cause ping at cruise during lean cruise mode.


Yup, good call. Looks like your 85 is "too new" for another carb. Good luck.

But, I will reaffirm my point on Edelbrock. Put a #1406 on a 70's Pontiac 455 and everything was better, never a problem. That + a Performer manifold, better mileage, performance, reliability, etc.

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#4514578 - 09/12/17 08:18 PM Re: 1985 Olds 88 carburetor question [Re: JimPghPA]
clinebarger Offline


Registered: 12/19/13
Posts: 1902
Loc: Fort Worth, Texas
Nothing at all wrong with increasing the curb idle just a little, The adjustment screw is on the drivers side of the carburetor, The head of the screw faces forward, Clockwise to increase idle speed.

The "Idle-Up" solenoid is only active with a A/C on, If the cold starts are easy....The Choke is most likely working!

If the electronic mixture control solenoid is faulty or a control issue is present.....It will run PIG RICH once it warms up & can cause a low curb idle.

You can get rid of this mess by changing the Carburetor AND the Distributor that has Mechanical & Vacuum Advance. Set the total mechanical advance at 34 degrees BTDC all in by 2500 rpm, Limit the added vacuum advance to +10 degrees (44 degrees BTDC), I generally hook my hand held vacuum to the Pot & check the total. When done hook the vacuum advance to Manifold Vacuum.
The above advise is assuming NO functioning EGR!

A good non-electronic mixture QuadraJet would be my choice as I personally do not like Carter AFB/Edelbrock Performer carburetors or ANY square bore carburetor on such a small low output engine....The Primaries are just too big!
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