The Wankler

iTrader: (14)

When I bought my car from a youngster, I do not recal this beig hooked up to the harness. Is it supposed to?

HAILERS

Sorry, that's not the Air Supply Valve. That is the Air Bypass Solenoid used only during cold starts.

The Air Supply Valve is on the back of the throttle body. It's in that picture. Below and to the left of the throttle cable support. Sort of off gold in color. Cylinder. Two wire connector. Used for pwr steering idle assist. It does something else that NZConvertible keeps reminding me of that I can't remember right now.

NZConvertible

Hot start assist.

Leave that solenoid unplugged, it only does bad things. Actually it only does one bad thing, a 3000rpm cold idle...

WAYNE88N/A

NZ, I see you haven't been following my narratives with Hailers lately- that valve is not needed for the 3K warmup. It may be energized during the process, yes, but it's not solely responsible for the amount of air bypassed. The BAC can do it all on its own...

And I don't consider a 3K idle for 17 seconds a bad thing, especially if you're premixing

HAILERS

And I never said it was the sole contributor to the accelerated warm up. I said, and said it long ago, that I notice that if that items plug is left off, the rpms drop from approx 3000rpm down to the 2300 range. Wayne, admit it, your car is honked up. humor

The rest of the time it's useless. And just in case, we're talking about the Air Bypass Solenoid on a series four engine. On a series five it's called another name but like the dude said *a rose by any other name is still a rose*.

WAYNE88N/A

I wonder why mine hits 3K and yours only hits 2300? It's like my BAC can bypass more air than yours. Is this your turbo car that this malfunctioning BAC of yours is on?

Let's not turn this into another 4 page treatise, though...Just tell me why you think you're only hitting 2300. That will suffice...

NZConvertible

...on your car. But judging by the many threads I've read on this subject, you seem to be on your own on this one. I don't know why this is, but for most cars removing that solenoid does drop that idle speed down from 3000rpm.

But assuming for a moment that what you say is true, this poses two questions. If it isn't for the 3000rpm start, what's it for? And if it does nothing, why not just remove it?

You do know that most engine damage takes place immediately after starting the engine, while the cold oil is reluctantly being pushed back up into the engine? Why on earth would you want to make that worse? Premix is only affecting part of the engine.

WAYNE88N/A

Yeah, I want to figure this one out. I know for a fact that my mechanical idle is adjusted perfectly; with no BAC in the loop and no loads, she idles at 750 dead nuts. Sometimes the 3K warmup actually goes to about 3200, all by the BAC.

It's funny, I actually took the ABP valve and relay off the car to get rid of the 3K thing, lol...

I don't agree with the engine damage thing, NZ, there are only the 4 bearings you're actually worried about when starting her cold, and they'll still have the oil film, and oil pressure comes up really quick after start- probably quicker than it does when she starts at 800 rpm, or 1500, or whatever...Besides, there's no load on the engine at all, it's not like you're starting the car and immediately driving off at 3 grand.

And, I rebuilt at 186K, even though she still had life in her. If it gets damaged as much as you say, the bearings would have been shot, at the very least, wouldn't you think?


I always figured the ABP was just for the AC and power steering anyway; you gotta figure, it's just an on-off valve with a certain sized hole, probably sized by the engineers to almost exactly allow the air necessary to keep the idle stable with the compressor on, or the steering pump loaded...

If Hailers is right, the ABPV opens on start (his conjecture, the rest is mine), but it doesn't allow enough air to hit the 3K, so the BAC kicks in to get her there. Without the ABPV, the ECU just kicks the BAC in harder. Mine happens to work better than most. My latest theory about the whole shebang, anyway

NZConvertible

There are many more people who don't premix that those that do...

imdrax

iTrader: (1)

not to bring from the dead or anything but im getting rid of some stuff to clean up my engine bay. is this air bypass solenoid valve removable without any adverse consequences? can it simply be removed and plug the hole to the TMIC and to the dynamic chamber?

NZConvertible

Yes and yes.

imdrax

iTrader: (1)

thanks alot while ive got your attention.... ive been trying to reasearch emission/air control removal. here is my list of things i will be removing that to my knowledge will not affect idle and/or driveability: BAC,A/C, Air pump, Air suply Valve, Air bypass solenoid valve, Air control Valve, Egr valve. and am i also correct in assuming that all relative vacuum lines can be simply plugged? thanks for any response as i have been researching this very thouroughly and want to be 100% positive on the affects and you seem to be very knowledgeable with FC's.

NZConvertible

I don't see any reason to remove the idle control items (BAC valve and air supply valve). There's no advantage to removing them. If you don't need to pass emissions checks than the air pump, ACV, air bypass solenoid valve and EGR valve can be removed.

imdrax

iTrader: (1)

well from what ive read the BAC is only there for idle control when the A/C is activated during idle. and on my car the A/C has already been disabled and will be taken out this weekend. so i mean i guess i could leave it in if it is inoperative. does the computer use the BAC to correct idle in any other situations? and the air supply vavle as i have read from a few posts by you and hailers is there for the AWS and if removed will allow the car not to idle at 3k directly upon startup.

NZConvertible

Yes it does, that's why I don't see any point to removing it. The ECU uses closed-loop correction to maintain a 750rpm idle as loads on the engine change, mostly from the alternator. With a lot of electrical items turned on the alternator puts a significant load on the engine.

Correct. It'll still idle high for the first half-minute or so because the BAC valve also contributes to the AWS. Mines goes to ~1500rpm.

imdrax

iTrader: (1)

ok thanks alot. im going to hit it hard saturday and ill update with hopefully good results