joeld

Hey guys. I have a 86 Firebird-305 Carb-Engine Code H with Auto Trans. My question is, when does the throttle solonoid activate? I was thinking it was only energized when the AC was turned on. But, guess I was wrong as I noticed mine would extend with ing switch on. To me this doesn't seem right as this does cause a high idle condition when AC is off. Of course this might be the reason the car has always had that problem.

Thanks,
Joel

five7kid

iTrader: (14)

It will always be energized when the AC and ignition are on.

It is energized by the ECM during certain driving conditions. You don't hardly notice it, though.

It shouldn't be energized idling with the AC off, though.

joeld

Yea, that is what I was thinking also. But nothing has been done to this car that would affect the wiring. I changed the relay today, same condition.

Sorry for the double post. trying to delet now

Joel

eightTfourTA

iTrader: (3)

Sometimes those solenoids get physically stuck, I had a couple of them that always seemed to get hung up long after the voltage was off.

joeld

Yea, I've had a few hang up also years ago but this one works fine when voltage is removed. I just can not remember this solonoid energizing with only the ing switch. I had it in my mind that the AC had to be on. Was hoping someone with similar set-up could check theirs. I did drive the car around some today, good idle with AC on, a little high AC off. Thanks for the reply. I've got to break down and buy a Service Manual.

Joel

eightTfourTA

iTrader: (3)

If it's any help, mine (1984 L69/auto running a 1987 LG4 ECU) has always energized with just the key on, and with the A/C on. It also kicks on when decelerating above 35mph, then seems to come off when the torque conv unlocks; I figured it's to facilitate the torque converter lockup from that little bit of drivetrain slack, like you'd feel on a stick shift. I've got the solenoid adjusted to give it a 50rpm increase, as per factory spec on my cowl sticker. I've noticed these solenoids on non-a/c automatic cars, too.

joeld

Thank you very much for that info! I was over-thinking this. I'm comfortable with mine working correctly now.

Joel

naf

iTrader: (7)

Just FYI but the solenoid will engage during deceleration under certain conditions, kinda takes the place of the vac/mech dashpot canister on older carbs.

On 87 models (and maybe some earlier) it is also connected to a low pressure switch at the power steering gearbox and will engage when low pressure is detected. Easy enough to check whether your car is equipped with this though as the switch is on the high side right at the box.

joeld

Yes, mine does have the pressure switch on the pwr stg hose. Thanks for the reply. I had just never paid any attention to this solonoid before, just noticed it wasn't working last week. Replaced relay, fixed that.

Joel

naf

iTrader: (7)

An alibi: There are two possible pressure switches on the power steering hose. One, normally open, to engage the fast idle solenoid, or throttle kicker and one, normally closed, to dis-engage the AC clutch. I've seen several of the later carb models with both pigtail connections but only the A/C switch actually present on the high side. 'Course in South Carolina I only come across factory A/C cars.

It's illegal to drive a car here without A/C...or should be.

joeld

OK, you got me to thinking more on this. So it would appear that the switch in my pwr strg hose must be for the dis-engage of the AC. Reason for saying this is: I disconnected the pwr strg hose switch and turned ing switch on. The solonoid engerized and extended. So I really still do not understand what the function is of this solonoid. To be more clear on my solonoid, there is a single dk blue wire connected. This would appear to me as a simple on/off type function. Still looking for a FSM, hope to find one soon.

Thanks for all the imput, feel free to add more.
Joel

naf

iTrader: (7)

In your case, as stated above, the fast idle solenoid should engage whenever the A/C is on in order to compensate for the additional load of the compressor at idle. The ecm will also engage it during specific deceleration periods in order to prevent surging and 'backfire'. It should not be engaged at idle with A/C off - unless you have the power steering pressure switch for it and the pressure is low.

It's engaged by applying 12volt to the single wire connector, grounded through the body of the solenoid.

The A/C pressure switch on the steering hose breaks the voltage to the A/C clutch. You can verify by continuity check to the clutch connector.

Auggie

I have a 1984 Z28 that only has one sol. and does all of the above stuff. My sol. though has a hex on the shaft and can be adjusted I think with a 1/2" wrench. I had to install another sol. (see pic) for the idle speed adj. because of engine compression and run-on. I unscrewed the Idle speed screw and use the second sol. for engine idle speed. When I turn the key off the sol. is dengerized and the throttle plates close all the way which prevents the engine from run-on.

joeld

Hey Auggie, that looks like a nice set-up. So, you are using the 2nd solonoid for the AC compensation? How did you wire it in? Did you use a relay or just splice a wire for power?

Joel

Auggie

Joel, the sel. closest to the carb is the origional sol. and that is used for the A/C ect., ect. The outter sol. is used for engine idle speed. I wired that sol. to the fuse box ign. sw. in the run pos.

Auggie

Ang

My solenoid comes on and off with the AC in position. No Problem

I also comes on @ 40mph accelerating and when I go under 40 the thing sticks in the extended position until I flick the gas pedal to knock it down. I also think it is physically sticking but it works on/off with the AC.

I have to look for the switches on the PS.

Why on at 40? Any words of wisdom?

Ang

Auggie

My origional sol. (clostest to the carb see post #13) has power when the key is in the run pos. but dosn't have enough power to move the throttel against spring tension. I can feel that sol. turn off when my foot is on the gas pedel at 30 mph every time unless the AC is on.

Auggie

joeld

Hey Ang, I wish I could give you some "words of wisdom" on this sol. Have no idea why yours would energize at 40 mph. I do agree with Auggie on the sol usually not having enough kick power to move the throttle lever on it's on. The throttle has to be opened slightly for the sol to "lock" in it's extended position. I would suggest on your issue to check the operation of your throttle return spring for good smooth function. I have had these springs to bind up due to lack of lubrication/rust etc. Try some WD-40 followed by some light machine oil on the return spring. Good luck

Joel