85 idle
Thread Starter
Racer
Joined: Oct 2013
Posts: 483
Likes: 19
From: las vegas nv
85 idle
okay after changing the iac, cleaning the throttle body,set tpm...new plugs,wires distrubutor,distributor,, vacuum lines..it fires literally right up..idles alittle high ( I set it that way) it purrs...gets to a temp of 130-135..drops ..still idles but a little struggle..then at 160-165...she is spot on...smooth... I wish I had some hair to pull but...at 60...im lucky I can still get in and out..lol..any help at all or suggestions please
Advanced
Joined: Feb 2018
Posts: 86
Likes: 11
My 85 idles fine 90 percent of the time. Sometimes when comming to a stop the idles surges ever so slightly. I attribute the odd idle to the old computer the runs the car. It doesn't have the soffisticated computers that new cars do. Had a guy ask me if it does that often. He worked on one for a customer that did the same thing.
Just because you put new parts on the car doesn't mean the parts are working properly. Your new parts could be faulty, happened all the time when I was a mechanic. If you want to continue to throw money into parts the mass air flow sensor and the coolant temp sensor for the computer. MAF sensor determines engine load and can cause idle issues (not common). Coolant sensor is the "choke" for the engine. It tells the computer how cold the engine is and the computer adjust the fuel amount. That doesn't usually cause idle issue at an in-between temp like that but anything is possible I suppose.
A better description of the idle issue would be handy. Is it running rich or lean? Just a low ideal? What does the tach say? You're doing a lot of work to get a specific idle at a temperature the car doesn't operate at for an extended period of time.
Just because you put new parts on the car doesn't mean the parts are working properly. Your new parts could be faulty, happened all the time when I was a mechanic. If you want to continue to throw money into parts the mass air flow sensor and the coolant temp sensor for the computer. MAF sensor determines engine load and can cause idle issues (not common). Coolant sensor is the "choke" for the engine. It tells the computer how cold the engine is and the computer adjust the fuel amount. That doesn't usually cause idle issue at an in-between temp like that but anything is possible I suppose.
A better description of the idle issue would be handy. Is it running rich or lean? Just a low ideal? What does the tach say? You're doing a lot of work to get a specific idle at a temperature the car doesn't operate at for an extended period of time.
Last edited by BowerPower; Mar 18, 2021 at 04:45 AM.
Safety Car
Joined: Aug 2009
Posts: 3,751
Likes: 275
From: Melbourne, Victoria, Australia
okay after changing the iac, cleaning the throttle body,set tpm...new plugs,wires distrubutor,distributor,, vacuum lines..it fires literally right up..idles alittle high ( I set it that way) it purrs...gets to a temp of 130-135..drops ..still idles but a little struggle..then at 160-165...she is spot on...smooth... I wish I had some hair to pull but...at 60...im lucky I can still get in and out..lol..any help at all or suggestions please
The usual issues are below
The throttle body screw has been adjusted - means redo the base idle setup (google it)
The EGR exhaust gas recirculation valve not seating, allowing exhaust to enter inlet at idle. -Check with flashlight suck on the hose check it lifts and drops down fully.
Leaking intake runner gaskets or loose bolts- replace gaskets / tighten bolts. (using a propane blowtorch just a little bit near the intake runners see if idle speeds up in areas)
I have an 85 with smooth stable idle, factory std should run around 600 rpm (580 rpm hot via ecm idle temp settings).
Start should have a high idle for a few moments, 1200 rpm then settle to 600 rpm fairly quickly.
Cold start will be a little higher until warm via the ecm idle temp settings.
There was a GM recall to adjust base idle setting speed from 400 to 500 rpm in drive, to resolve a stall complaint. (Google base idle setup for procedure).
Cheers
Team Owner
Joined: Jul 2004
Posts: 28,431
Likes: 3,284
From: Hartford WI
That procedure is fine IF everything is stock AND everything is perfect. So no leaks, tach is right, timing is right, etc, etc. Any one thing is wrong and you have something else. IDK if an 85 can be read by common scanners but I would check the IAC counts at hot temps and in closed loop to figure out what the idle is supposed to be at as commanded by the ECM.
