David Trimble

Ok, got another question for you guys

The fast idle A/C solenoid, I noticed while I was checking the voltage on my TPS was engaged. Curious, I checked to make sure my A/C wasn't turned on (this was without engine running, btw) and it wasn't.

The only times that I know of that the solenoid should be engaged is when you've got the A/C on (duh) or if you're decelerating with the foot off the pedal, when it will engage briefly so you're not immediately slamming the throttle closed.

Does anyone know why the solenoid would be engaged with the engine not running?


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Original owner - '84 T/A w/stock 305HO 5-speed

Damon

It wouldn't unless its gone bad. Now I don't know EVERY Qjet application every devised but there were a few that did not rely on a standard idle speed screw to set warm idle speed (wlthough there still was a screw there to set a bare minimum curb idle if the solenoid failed). They had something on them that LOOKED like an A/C compensator but it wasn't- it was a full-time speed soenoid controlled by the computer to set idle speed at all times (once the choke pulled off, anyway). That may be what you've got. If so, its possible the ECM is probrammed to go back to some pre-set opening point at engine shut-down.

No promises here, though. I could every easily be totally upside-down on this.

Just thought of one other possibility- this solenoid may just run the reverse of what most solenoids do- it's DEFAULT may be to extend and advance the idle and require it to be turned on (energized with 12v) to retract.



[This message has been edited by Damon (edited November 07, 2000).]

David Trimble

Well I got to thinking- I'll bet that the solenoid is kicked out by the ECM when it's apparent to the ECM (by whatever means is available) that the engine isn't running and the ignition key is in the 'on' position. I had noticed that while the engine runs the solenoid doesn't kick out unless of course you've got the A/C on. So it may be out as a aid to starting the car by giving it part throttle. This is the only theory I could come up with....

Damon

Could be. Try just unplugging it and see if it's default position is IN or OUT. If the car isn't turned on the ECM can't be energizing it and it will return to its default position.

Also, I thought of somethign else. When you start the engine first thing in the morning, engine cold, the choke will be ON (closed). When the choke is closed it also sets the idle speed up a little (its part of the fuctioning of the choke linkage) and it's possible this is why you are seeing slightly higher TPS readings.

David Trimble

I was tinkering with the carb the other day and I noticed that the solenoid was deenergized. So it's not doing it all the time. I suspect that it is ECM controled tho as the A/C was definately off at the time when I noticed that it was engaged.

Also I did try disconnecting the solenoid and the plunger would retract, so it has to be energized to engage the fast idle.

As to the TPS reading- yes that might be it as I'm getting .58 at idle and I think it's supposed to be .48 or thereabouts. So the ECM might think it's at fast idle. Hard to tell tho as I've got a idle problem where it's running lean at idle (dwell < 10 degrees fixed). The carb's out of adjustment most likely according to the board gurus (I had it apart about 2 months ago but I never touched the adjustments- however the idle problem started shortly after this) so the ECM's probably confused as to what the carb is doing, and thus might be engaging the solenoid when it doesn't need to.



[This message has been edited by David Trimble (edited November 14, 2000).]