Idling issues

[MrFoMoCo]

After I rebuilt my 4180 I have been having idling issues. As a matter fact, it won’t idle at all. As soon as I lift my foot off the accelerator it goes dead. I replaced all spark plugs(they needed it) hoping it would help and still nothing.
During the rebuild I did not touch the idle air screws.
Stock 85 GT 5 speed.
Any suggestions?

[85stanggt]

I would say you need to adjust your idle fuel mixture with the four corner screws, but it shouldn't be that far off if it ran great before you rebuilt it. Before diving in to adjust the idle mix, check the basics first...

Are there any vacuum leaks -- a line left off, etc. Check the 4 front vacuum ports.
Did you adjust the fuel bowl levels primary and secondary?

If you go adjust the idle mixture, first turn the screws all the way in to seated and count the number of turns. Write them down so that way you at least have a baseline of how it was before.

[Walking-Tall]

How far 'on' does your foot need to be to keep it running?

If a bunch, I'd say the primary idle circuit passages within the metering block and within the main body need to be better cleaned out. I'll show some reasons in photographs below, why an over-and-above extensive cleaning (lots of "carb cleaner" sprayed through (all four primary idle air bleeds and the main body base passages that are equipped with upturned "e-tubes" with tiny side holes) both directions, and lots of compressed air blown through in both directions) than usual is necessary due to areas where debris gets held onto...

If just a bit... is the primary idle speed being maintained, bumped up/open with the idle solenoid do-hicky?


Reasons why 4180's, as is, require very VERY thorough cleaning of the primary idle circuit passages at rebuild time:








Link to a look at my ongoing thorough investigation into the inner workings of 4180's:
http://vb.foureyedpride.com/showthre...-Holley-4180-s

[MrFoMoCo]

Thanks for all the advice.
I spent a ton of time on the fuel bowl levels before I even fired it up. I probably should check that again. It couldn’t hurt.
It is always possible I left hose off. I hope it is that easy.

It is possible the idle solenoid is bad. It is an original unit. Any way to check if it is working?

[85stanggt]

The idle solenoid will only activate when the A/C is on. It bumps up the idle about 200-250 rpm to compensate for the drag of the compressor on the engine.

You can test it by turning on the A/C. Your idle will likely decrease from the added load. Lightly press your foot on the gas, barely enough to crack the throttle. I feel the solenoid click up and it holds the idle higher after that.

Even better, turn on the A/C with the air cleaner off and lift the throttle by hand. It'll hold up the set screw. You can then unplug the electrical connector to it and watch the solenoid drop back down.

The solenoid itself wouldn't prevent your car from idling.

Did you alter any adjustments during your rebuild? Did you use a Holley kit?

[Walking-Tall]

The idle solenoid will only activate when the A/C is on. It bumps up the idle about 200-250 rpm to compensate for the drag of the compressor on the engine.

You can test it by turning on the A/C. Your idle will likely decrease from the added load. Lightly press your foot on the gas, barely enough to crack the throttle. I feel the solenoid click up and it holds the idle higher after that.

Even better, turn on the A/C with the air cleaner off and lift the throttle by hand. It'll hold up the set screw. You can then unplug the electrical connector to it and watch the solenoid drop back down.

The solenoid itself wouldn't prevent your car from idling.

Did you alter any adjustments during your rebuild? Did you use a Holley kit?

Learn something new everyday. Thank you. All sorts of those idle solenoids were in place to be adjusted to maintain curb idle speed with the key on, and bump up the idle speed with extra load on the engine, like with A/C, and also to completely de-energize when the key's turned off, then more-so completely closing the primary throttle to try to minimize the smogger engines' tendency to "run on" after shutdown.

Good ideas for checking it.

From the sounds of the symptoms, and the unacknowledged suspected suggested issues and unanswered suggestions/questions above, I would highly suspect primary idle circuit blockage, somewhere between the idle feed restriction/s right behind the primary jets, to the unnecessary dirt-collecting brass tube restrictions in the primary metering block, to the multitude of interconnected passageways for the four primary idle air bleeds, to the unnecessary dirt-collecting brass tube restrictions at the bottom of the base plate face of the main body... after all that, in the base plate, is nothing but transfer slots and idle mixture screw tips and discharge holes... earlier I was going to suggest deteriorated o-ring material may be an issue or a blockage factor in the base, but even if they are toast, those wouldn't be able to migrate through the threads and get to being blockage of the mixture screw tips and discharge holes.

Yes OP, a vacuum leak or a left-off (or deteriorated) vacuum hose or cap would produce non-idling, and running out of gas sort of symptoms...

[MrFoMoCo]

The idle solenoid will only activate when the A/C is on. It bumps up the idle about 200-250 rpm to compensate for the drag of the compressor on the engine.

You can test it by turning on the A/C. Your idle will likely decrease from the added load. Lightly press your foot on the gas, barely enough to crack the throttle. I feel the solenoid click up and it holds the idle higher after that.

Even better, turn on the A/C with the air cleaner off and lift the throttle by hand. It'll hold up the set screw. You can then unplug the electrical connector to it and watch the solenoid drop back down.

The solenoid itself wouldn't prevent your car from idling.

Did you alter any adjustments during your rebuild? Did you use a Holley kit?

I was very careful not to alter any adjustments. A Holley kit was used.

I actually was experiencing this issue before the rebuild, although not as bad. It would at least idle a bit before. It is why I decided to rebuild the carburetor. It needed it anyway since it was filthy. My problem may not be in the fuel system.

I cleaned the passages again as suggested by Walking Tall. We will see if that works.

I have double checked the vacuum lines as well.

When it does run, it runs pretty rough. I may have an ignition problem has well. I have the original FoMoCo distributor cap. I will probably get a new cap and rotor as well.

Thanks again for all the advice.

Edit...
After following some of the advice above. Making sure all the air bleeds were thoroughly cleaned out, readjusting the fuel bowls, testing the idle solenoid etc and changing the distributor cap and rotor I was able to get run great.

Thanks again!

[Walking-Tall]

Nice