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1985 Olds 88 carburetor question #4514434
09/12/17 06:00 PM
09/12/17 06:00 PM
Joined: Aug 2009
Posts: 3,899
Pittsburgh,PA U.S.A.
JimPghPA Offline OP
JimPghPA  Offline OP
Joined: Aug 2009
Posts: 3,899
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.


Boy will I be happy when ALL vehicles on public roads are autonomous.


JimPghPa

Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514438
09/12/17 06:04 PM
09/12/17 06:04 PM
Joined: Aug 2009
Posts: 3,899
Pittsburgh,PA U.S.A.
JimPghPA Offline OP
JimPghPA  Offline OP
Joined: Aug 2009
Posts: 3,899
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.


Boy will I be happy when ALL vehicles on public roads are autonomous.


JimPghPa

Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514441
09/12/17 06:07 PM
09/12/17 06:07 PM
Joined: Sep 2014
Posts: 1,446
Toronto Canada
WobblyElvis Offline
WobblyElvis  Offline
Joined: Sep 2014
Posts: 1,446
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

Last edited by WobblyElvis; 09/12/17 06:08 PM.
Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514457
09/12/17 06:22 PM
09/12/17 06:22 PM
Joined: Jun 2003
Posts: 17,342
Deplorable in apple valley, ca
Chris142 Online content
Chris142  Online Content
Joined: Jun 2003
Posts: 17,342
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.

Last edited by Chris142; 09/12/17 06:23 PM.

02 Wrangler durablend 10w40
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Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514466
09/12/17 06:33 PM
09/12/17 06:33 PM
Joined: Sep 2015
Posts: 1,523
USA
mk378 Offline
mk378  Offline
Joined: Sep 2015
Posts: 1,523
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.

Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514474
09/12/17 06:45 PM
09/12/17 06:45 PM
Joined: Jun 2003
Posts: 33,071
ME
eljefino Offline
eljefino  Offline
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Posts: 33,071
ME
If there's a solenoid that keeps the throttle propped open at idle check that it works.

Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514483
09/12/17 07:07 PM
09/12/17 07:07 PM
Joined: Aug 2005
Posts: 905
dayton oh
kc8adu Offline
kc8adu  Offline
Joined: Aug 2005
Posts: 905
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.

Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514485
09/12/17 07:08 PM
09/12/17 07:08 PM
Joined: Oct 2004
Posts: 7,962
Cincinnati, OH, USA
bullwinkle Offline
bullwinkle  Offline
Joined: Oct 2004
Posts: 7,962
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.


06 Ram 3500 CTD 4X4(FG Venturi), 93 GMC C3500 6.2, 89 F-450 7.3, 98 XJ 4.0(XG8A), 05 xB(XG3600), 18 Transit 3.7, 03 Merc Grand Marquis 4.6 2V(XG2)
Re: 1985 Olds 88 carburetor question [Re: eljefino] #4514490
09/12/17 07:11 PM
09/12/17 07:11 PM
Joined: Aug 2005
Posts: 905
dayton oh
kc8adu Offline
kc8adu  Offline
Joined: Aug 2005
Posts: 905
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.

Re: 1985 Olds 88 carburetor question [Re: kc8adu] #4514503
09/12/17 07:21 PM
09/12/17 07:21 PM
Joined: Jun 2003
Posts: 33,071
ME
eljefino Offline
eljefino  Offline
Joined: Jun 2003
Posts: 33,071
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.

Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514510
09/12/17 07:25 PM
09/12/17 07:25 PM
Joined: Aug 2005
Posts: 905
dayton oh
kc8adu Offline
kc8adu  Offline
Joined: Aug 2005
Posts: 905
dayton oh
the primary adjustment is the stop screw.
but the real fix is a rebuild.

Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514511
09/12/17 07:25 PM
09/12/17 07:25 PM
Joined: Oct 2011
Posts: 1,372
CA
user52165 Offline
user52165  Offline
Joined: Oct 2011
Posts: 1,372
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

Last edited by user52165; 09/12/17 07:31 PM.
Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514521
09/12/17 07:31 PM
09/12/17 07:31 PM
Joined: Aug 2005
Posts: 905
dayton oh
kc8adu Offline
kc8adu  Offline
Joined: Aug 2005
Posts: 905
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.

Re: 1985 Olds 88 carburetor question [Re: kc8adu] #4514535
09/12/17 07:43 PM
09/12/17 07:43 PM
Joined: Oct 2011
Posts: 1,372
CA
user52165 Offline
user52165  Offline
Joined: Oct 2011
Posts: 1,372
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.

Re: 1985 Olds 88 carburetor question [Re: JimPghPA] #4514578
09/12/17 08:18 PM
09/12/17 08:18 PM
Joined: Dec 2013
Posts: 2,177
Fort Worth, Texas
clinebarger Offline
clinebarger  Offline
Joined: Dec 2013
Posts: 2,177
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!


2001 Chevy Camaro L92/4L80E
2006 Chevy 2500HD LBZ/Allison 1000
2010 Toyota Corolla 2ZR-FE/Auto
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