I am not exactly sure what is going on here with my idle.
First off, I have a digital dash. So when I'm setting the idle air screw and I set it to what my gauge says is 400-500, I think I'm wrong to begin with in that sense.
I think that resulted in a high idle for a while, now I'm trying to fix it again. I have adjusted a new TPS to around 0.54 and I just put a new Wells IAC in.
I went to set idle, did the diagnostic paperclip jumper, the fans did not come on (maybe something to do with my new fan switches? they used to come on in paperclip mode..) But the check engine light blinked and I heard the IAC clicking but it's not the same clicking as my old one did. Disconnected the timing advance wire. Plugged the ALDL cable into my laptop and fired her up. My digital dash shows two notches in RPM, my computer days 575rpm (wow). Is this RPM higher because of the ALDL mode? I know when I'm not adjusting my idle the ALDL plugged in jacks the idle up, but is that disabled with the EST and IAC disconnected? By the way, the 575 idle, is with the screw almost and all the way off the stopper, barely holding the throttle plates open. Could it be the IAC didnt open all the way, still letting air in? The reason I started playing with all this is somewhat because when i have my headlights on, the voltage drops a tad, and my blinkers get REALLY slow, but if my idle rpm is higher, it's fine. So I thought possibly the IAC isn't kicking the RPM up or holding it at it's spot, when there's more load on the system, the same thing goes with my fans somewhat, when I have them both on, but it doesnt bog the voltage down as much as the headlights I don't think. I've tried searching a ton of threads, couldn't really find what I was looking for aside from the obvious vacuum leak suggestion, if anyone has a diagram of all the vacuum hoses, post it up.

The car is an '87 Trans AM, 305TPI, 210,000 miles

My questions to you the forums are:

1. Digital Dash wrong? 200-300 RPM on digital dash is 575 in WINALDL (and is WINALDL very accurate?
2. ALDL Mode higher idle, does it still make her idle higher with the timing advance and IAC disconnected?
3. Could the IAC still have been open, letting more air in? I let it sit for 30 seconds, clicking. Any way to know it's def. moving in and out? Since the counts are just what the computer wants it to do..
4. What's up with the idle voltage and the slow blinker?
5. There's one vacuum hose going from the cruise control area to under the battery, what's it go to?
I've sprayed alot of the hoses with carb cleaner, havent really found a leak, but the hoses aren't in the best shape either. A hose route diagram would be helpful..

 

Are you adjusting with the trans in "D"? What I like to do is stuff a small rag in the IAC air inlet in the throttle body to make sure all air is being cut off at the IAC. Since yours should be a MAF system, the air snorkel is going to have to be on after inserting a small rag in the IAC inlet. Minimum air rate is adjusted in drive. Is your TPS adjustable? If it is, it would be done after min air rate which is what sets the throttle angle. I would use an external RPM gauge to be sure whether yours is acurate or not.

 

thank you, that was a good suggestion, some interesting results.
jumped A&B, let IAC extend, removed jumper, disconnected IAC and timing wire.
started the car.

plugged the ALDL in and used WINALDL to get the real RPM
without blocking the IAC hole:
625RPM in PARK
525-550RPM in DRIVE

turned car off, blocked the IAC hole:
425-450RPM in PARK
400-425RPM in DRIVE

what could this possibly mean? I just put a new IAC in there, though i think it was probably acting like this before i put the new one in, because nothing really changed rpm wise from old to new ones.
things i've noticed, there's one of those curved things in there between the throttle body plates (I think it says hypertech on it) to smooth airflow, with a small slit on the bottom for IAC.
When I had the throttle body assembly off, one of the head of the bolts to the IAC part of it was broken off. there's still the rest of the screw in there though, looks like just the head broke off. the connector to the IAC is abit beat up, with half the plastic missing, but all the connectors go in the right holes, unless someone put the wires in wrong when replacing that connector at one point, but the IAC is clicking, so it's getting power.
also, the IAC is at 145 in WINALDL on both tests

 

So your saying the IAC counts are at 145 with the IAC controling the idle? With that at 145 the RPM's should be like 1200. Either there is no control to the IAC from the computer or the passage is blocked. Try removing the IAC motor and starting the engine being ready to shut it off. If the RPM doesn't increase there is a passage problem. If the RPM goes high, there is an IAC control problem, terminal connection problem, or maybe that hypertech, or something else is blocking the air inlet.

 

does 145 mean the IAC is closed all the way not letting any air pass or open all the way letting air pass?

I was setting minimum idle screw when doing all this, and after i did the IAC reset thing (paperclip), essentially, it should have been fully seated and closed..not letting any air pass? so the idle rpm should be the same with the IAC still disconnected, with me blocking it, or not blocking it off. but in fact, the rpm went down a good 125 when i blocked it off, suggesting air is somehow getting past it?

 

0 to 145 is the computer command range. If it wants to lower the RPM, it lowers the counts until it sees the desired RPM reading. If it wants to raise the RPM, it adds counts until desired. It's not where the IAC is acutally at. There is no reading from the IAC that can be read or measured to phisically show the position like a TPS. The computer sees the RPM and opens or closes the IAC to get the RPM it wants. If the RPM is too low, it will add counts. A 145 count reading says the RPM is not coming up to the desired Idle and has the IAC commanded fully open. So, one of 2 things: 1. the IAC passage is plugged, or 2. the IAC valve is not opening, caused by a mechanical malfuction of the valve, or electrical problem.

And, like you said, the RPM changed when you blocked it off, so, yes there was air getting past it. That's why I prefer to block the passage to do the adjustment instead of commanding the IAC closed. The pintle has a tendancy to get carbon on it, causing it to be held open a little. You said you replaced it so you should be fine. Another thing you could do is remove the IAC and with the connector connected, check to see if it's opening and closing. You have to be careful, the pintle will come out. Or manually check it with jumper wires to the battery positive and negative. Not sure which wires are which. But it sounds like it's electrical (or connections) or a valve/passage problem.

 

145 count = IAC fully closed? Meaning letting air get through?
That's what my computer showed me, 145, this was after I did the paperclip to the ALDL and waited a minute, then disconnected the IAC.
I thought it was 145 count means no air gets by, IAC fully extended.
However, this wasn't computer commanded, it was from paperclip mode.


Will a new gasket help or does the air first have to get past the IAC before the gasket comes into play, leak wise?

 

145 means the computer is trying to fully open the IAC. Like...O2 voltage high, .9volts, means rich. So, the computer sends a command, to lean the fuel with a higher dwell time (just like IAC counts), for carbs, or less injector pulse time, for fuel injection. It's a command. 0 counts would be to close the IAC all the way. I don't think the gasket has any affect.

 

so you are saying my iac is doing the opposite of what it's supposed to?
when i paperclip the aldl the count is supposed to goto 0 ?

 

What I'm saying is, your IAC is not opening, not letting air through, to increase the RPM to what the computer wants to see. The paperclip may be telling the computer to close, but the computer may not be able to control the IAC for whatever reason. Be it, the passage, or the IAC itself, or electrical problems. But it seems the computer is trying to do it's job.

 

ok so 145 is right.
i just ordered a new iac harness connector since mine's decently beat up. and im going to try to clean the iac area out, even though i noticed one of the heads to the screws broke off the bottom, that's going to be a problem..
will report back after i complete those, thanks for the replies