Stock idle rpm?

[SP 7M]

If you were actually asking for an explanation, then fine. You just seemed to come off cocky in your first comment, as if to suggest that I didn't know what I was talking about. That's why I responded in the manner that I did. Oh well, I'm often mistaken for being rude as well, so no big deal.

I don't remember off the top of my head how to adjust the idle on the '89+. If you look around the back side of the TB while the car is running and experiment with the assembly that the throttle cable is hooked to you'll probably figure out what to do to adjust the idle. I believe that there is a tiny bolt with a locknut on it that did the trick for me. Just be careful not to adjust the wrong piece of hardware too much or forget what position it was originally set at. If you have a paint marker or something similar (what all that hardware was marked with from the factory) you can mark the original position of each bolt.

The picture that Staticpat has is from the pre-'89 throttle body. The '89+ doesn't have that screw on it.

 

[jetjock]

Well, in all fairness you really don't know what you're talking about. What we have here is a debate between an electrical engineer and a guy who can't wire up a fan, who by his own admission knows little about and hates electronic stuff and a guy who has to take his car to a dealer for work. Since the ISC system on a Supra is electronic that leaves me confused but I'll still take the time to try and educate you.

Sure the idle can be adjusted the old fashioned way by cracking the throttle plates with the throttle stop screw but you'd better disconnect the ISCV or it'll always be trying to compensate. The best way to do that would be to shut the engine off first so the valve steps all the way open, then unplug it. You could also jumper the diag block, set idle speed using the bypass screw on an 87 or 89, then unplug the ISCV. Heck, you could even install a calibrated orifice in the ISC hose sfter unpluging the valve.

Why anyone would do any of that is beyond me as they'll loose all the benefits of closed loop idle control. His problem is obviously something else and he needs to find it rather than taking a giant step backwards by controlling idle with the TB. Such a method would also require recalibration of the TPS's IDL contact to the throttle plate as well as readjustment of the decel dashpot.

Me mistaken for being rude? No!

 

[SP 7M]

Well, in all fairness you really don't know what you're talking about. What we have here is a debate between an electrical engineer and a guy who can't wire up a fan, who by his own admission knows little about and hates electronic stuff and a guy who has to take his car to a dealer for work. Since the ISC system on a Supra is electronic that leaves me confused but I'll still take the time to try and educate you.

Me mistaken for being rude? No!

Ok, well I'm just a mechanic that works on '68 and '69 Sikorsky CH-53Ds, a supervisor and a maintenance inspector but if my electrical skills don't impress you, then I must apologize. I guess I'll just go get a degree now for something that I have absolutely zero interest in just to come off as if I know what I'm talking about to you. Oh and I only did a MHG job on my Supra 2 1/2 years ago (admittedly before I was experienced enough) but since I want to make damn sure that my electric fan is wired somewhere safe (to keep my engine from overheating), I must not know what I'm talking about. Or if I don't know the best way to adjust the idle on a Supra... yeah, you get the picture. I suppose I should've included "somebody please correct me if I'm wrong," which I often do.

I can be sarcastic and have a good time with people on here all the time and I also often probably seem as if I'm rude (maybe I am). I guess I go about it in a different manner than telling somebody who I only have a couple forum posts of knowledge on that they don't know what they're talking about. If you want to go on and judge me when you haven't the slightest idea about me, then have a good time. I won't feel sorry for you.

I see that you left a "" at the end, as if to say that you didn't fully intend to seem rude, which I appreciate. At least you ended such an inappropriate statement with a hint of humor.

I'll talk to you and get along fine unless you refuse to do so.

 

[jetjock]

Lol, easy there Big Fella. My point was that you didn't know what you were talking about regarding the Supra's idle system and you don't. That has no bearing on you knowing how to wrench on CH-53Ds. I'll say this though, unless you're military you must be a certificated A&P. Fwiw I've never met one yet that was electrically competent, which is odd considering I'm quite familiar with the training they receive and the materials used for their certification. I've also never met one I'd let anywhere near my own aircraft without my being there to supervise. The ones' I trust my life to on the job make me nervous enough.

Thanks for olive branch but there won't be any need for us to talk beyond this because there isn't anything you could possibly teach me about this car. Since the opposite doesn't hold true it'll be your loss, not mine. And yeah, you are rude. There is no mistake involved. Or at least very thin skinned. No doubt it's because you're a youngster.

As for your initial post I was just surpressing misinformation, which would be a full time job here if I chose to accept it. Aloha

 

[SP 7M]

You're quite full of yourself, or at least portray that attitude by the way you speak. You're also, at very least, a judgemental person.

I offered to talk to you because there may be other things that we have in common, but again, because I know less about you than Supras (I really don't give a shit anyway) you don't want to talk to me. Fine. I'd be better off not talking to you anyway.

I really don't care about who works on your aircraft (oh, can't you do it yourself?) and I have earned the confidence of everyone in my squadron appointed above me that had to approve the designation of the qualifications that I possess. Whether it be to ensure that the plane is safe for flight (pilots know dick about what they're looking at), which I don't do anymore because I've moved on to bigger and better things or to be the night shift supervisor of the biggest shop in my squadron, I've earned my place.

Thin-skinned? Ahahaha! You don't even know, buddy! People like you entertain me. Yes, people like you.

I guess the basis of your arguement is that I'm only a 23 year-old. Keep on that point, I wouldn't want you to lose any steam. I must be completely incompetent because I'm so far short of your life experience.

Good day, sir.

 

[IJ.]

<mod hat on> Keeping an eye on this guys!

Please try to remain as civil as you've both been and it'll be fine! <mod hat off>

 

[SP 7M]

LMAO! You're a funny SOB, IJ! Mod hat?! HAHAHA! I've never heard that one before. It made me think of a plain, cheap black hat with a straight bill that says "Mod" in big white letters.

I'm always civil. Apprently the smiley with the halo has been deleted. I was going to place that here.

 

[IJ.]

LOL don't make me put my Mod Cape and Underwear on !!

 

[jetjock]

<mod hat on> Keeping an eye on this guys!

Please try to remain as civil as you've both been and it'll be fine! <mod hat off>

As I said, they don't know what they don't know. It's like shootin' fish in a barrel

 

[SP 7M]

You're hitting the right spots, as always, IJ. Those underwear would definitely be briefs-the cheap kind.

 

[figgie]

Hey guys

a dig up from the grave... but i think it is necessary.

The way i have adjusted my idle via the tb


there is a blocked side screw on the tb that you can remove the aluminum plug. After that their is a bleed screw. I always set idle that way so as to not muck with the tps. Is it meant for that? Got me.. pictures later on.

 

[JustAnotherVictim]

That screw won't do you much good adjusting.

The ecu will compensate for whatever you did to it afterwards. You'll end up back where you started.

 

[figgie]

That screw won't do you much good adjusting.

The ecu will compensate for whatever you did to it afterwards. You'll end up back where you started.

au contraire....

I have been adjusting that bypass screw since 1994 in my car without the ecu adjusting it. 1000 rpm idle and it stayed at 1000 rpm for about.. ohh 3 years until I got the issue I was having sorted out, then back down to 650 where it stayed until it's death in 2004 (7 years and nearl 190,000 miles later).

 

[JustAnotherVictim]

Telling you what it's supposed to do.
Usually means whatever is wrong is still wrong.

 

[jetjock]

I'll tell you what I know even though it's been some time since I did the experiments. As long as the IDL contact is made the ISC system on my engine corrects for changes in idle no matter the source of bypass air including the screw. Opening or closing (within reason) my idle bypass screw results in the ECU retuning the idle to target within 30 seconds.

Add to that my factory TCCS test instrument (which displays ISC motor stepping pulses) shows corrective stepping begins with appx a 25 rpm deviation from the current target (the TCCS manual spec is +/- 20). I can exceed the control range of the ISCV and effect idle if I go far enough with the bypass though. Of course, the valve ends up being offset during any of these shenanigans.

 

[figgie]

JJ thanks for that...

I was thinking about one thing regarding the ISC. Since there is no feedback. It assumes an initial position of 0 steps (completelyy closed) and start the "count" from there until target idle rpm is reached and then hold or counts back?

 

[jetjock]

As you said there is no positional feedback. That's why the valve is setup to home on engine shutdown. The homed position is full open to provided air past the throttle plate for starting. It's why cold start rpm starts off high. When rpm crosses 500 the valve begins stepping closed until it gets to a target based mainly on coolant temp. Oil pressure and a few other things also have a minor effect.

The target continues to roll as coolant temp increases until it reaches about 175F. At that point the fast idle algorithm ends and hot idle control starts. During this entire time the current target is compared against the NE signal from the CPS and held to within +/- 20 rpm. At least that's how it's supposed to work according to the books. Fwiw mine behaves this way.

Hot idle targets mainly involve headlight, defogger, AC, and electrical load. The AC target is special in that it also changes ignition timing. It's why when the AC is turned on the idle doesn't wait to dip but instead gets a "jump" on things.

Closed loop idle stabilization is done by advancing timing every time the O2 sensor swings lean. If you hold rpm at say, around 2000, and carefully listen to the engine and watch the tach you should be able to note a very slight hunting as the fuel loop swings between lean and rich. It can be used as a quickie check of closed loop operation. Anyway, this hunting is compensated for by the idle stabilization function when IDL is brought to ground. That involves the TPS of course.

Idle values are learned, same as the fuel trim values. The ECU remembers the number of steps it took to to reach an idle target and alters them over time to accommodate for wear, minor leaks, etc. Removing the EFI fuse erases the learned idle value. That's why idle behavior may be slightly off after a reset but the box will quickly relearn it same as it does for fuel trim.