guys,
i took the bottom cover off the throttle body and the iac plunger was about halfway along its travel,
i did the paper clip trick which is supposed to energise the relays and the iac didnt move,
i manually wound it in and i got the car to idle at 400rpm,
i reconnected it and it stayed in,
is this the iac or could it be the ecm?????
thanks,
natt

 

I am not sure I understand the procedure you have taken. Are you saying you took it apart to set the min.air (idle iac positon)?

 

i did the procedure to set the min idle according to lars paper,
couldn't get the idle below 900rpm,
figured there was a vac leak, checked the iac and it was half way out,
using the paperclip method it did not wind in,
so i took out the iac, wound it in manually the fitted it back in,
i could then get the idle at 400 no problem,
was just wondeing if it was likely to be the iac or the ecu not telling it what to do,
thanks,
natt

 

First, did it do this before you re-set the min air?
Yes it is very possible there is a vac leak, but I would first want to make sure the the min air was done correctly. When you ground AB you are in effect opening the IAC to close the air passage in the TB.
I wouldn't suspect the ECM, more likely IAC, vac. leaks, (TB, intake, hoses etc.)

Since I am not familiar w/ what you state here is what I do:
After the car is warmed up turn off car ground AB in aldl (paper clip), turn key to the on position ( not run) for approx. 30 sec. This put the stepper motor out closing the air passage.
Next unplug the IAC, then take paper clip off, re-start car let idle (you may have to coax it some) put car in drive w/e brake on. With a real tach of some sort set it to 450 rpm. in drive turn car off.
Plug IAC back in, depress pedal about a 1/3 start car run for 5 sec. turn car off , start again, let run for about 10 sec. turn off re-start. the rpm should go up (past target idle) to let you know the IAC is working properly. This is an mportant step!
Lastly re-check tps voltage an adjust if nessessary to .54 min.

It is also very easy to adjust the IAC to incorrectly:
If using the tach in the car and it reads high to begin with the TB blade could be then open (turning screw cwise) too much, which would then in effect put the min. idle above what the comp. can compensate (out of range)
Since you removed the IAC , did you clean it w/some TB cleaner, then a drop of oil on the stepper motor shaft? Being carefull on re-install in also need to be re-tracted.
Do you own a scanner, info there would help, because I cannot see the car I would be looking at this first. I like the idea of eliminating possibilities first, before tacing down other things.

 

Hi.
I have an85 and I am now not sure about one thing with this adjustment.
There are two alternatives that obviously are in discussion wether or not it is correct.

1. Shall the connector for the ignition control at the brake booster be disconnected when making the minair idle adjustment??

2. Shall the ECM be able to control the ignition timing during the min air idle adjustment??

I have not met anybody who can say that 1 is right or 2 is right.

Does anybody know.

Jan-Erik

 

1) According to the Helms and on the rad. shroud the est should be dissconnected
2)If using the Helms method the ecm will not be controlling the timing, since the est is dissconnected.

I have used this method and, ON MINE when the est was plugged back in it had an effect on the min. air setting that I didn't like, so I don't dissconnect to set min. air..........That's just me though

 

Not long ago there was a post on setting the IAC, one member posted a picture from the FSM..stating the EST should be disconnected, but it seems like all the tech writeups don't mention it..at least I haven't seen one. Wonder why?

 

My 86 manual says to disconnect the EST wire
http://members.shaw.ca/agent86/TB-TPS%2bMin-Idle.pdf

 

I believe Vader86's website says to disconnect the EST, but also says it may not be necessary.

 

In the 90 FSM in does state to disconnect the EST.
Certain tuners/wrenches don't believe in it 's importance as I have asked several how they set min. air etc. for a moded set-up.
I for one see that when diconnecting the est and setting the IAC would change the tb blade position (more angle less counts on a scanner). In other words with the est unplugged idle was lower to begin with, then by adjusting the min.air screw the TB blade would have to out further to idle @450 in drive. This was giving me less counts on a scanner than where I wanted it to be. This is just MY EXPERIENCE and I am not suggesting to anyone not to follow the Helns procedure for their particular year.

 

thanks,
mseven - when i ground AB in aldl (paper clip) the iac doesn't move,
i have a new one arriving in the morning, will let you know if it solved anything,
natt

 

I think that when you bridged A and B at the ALDL you are sending current straight to the IAC, not through the ECM.
Did you check the voltage at the IAC connection to see if it was getting current when the ALDL was bridged?
If there was voltage at the connection then replacing the IAC will cure the problem. If the new one that is ordered does not correct the problem or if there is no voltage to drive the IAC, you may have a bad connection in the wireing between the ECM and the IAC.
A few simple tests can sometimes save you money if done before replacing parts.

 

Natt, Let's hope it arrives in the morning. I sent it First Class, so they should deliver it tomorrow morning. Check your email for my response to your last. I have the bottom gasket and screws if you need them. Also a top gasket, not sure how much you disassembled.

 

When you ground terminal A and B of the ALDL it sends signal to the IAC to open up fully and block the air passage so that minimal idle can be set with just the throttle plates/TPS. You may not hear the IAC but try and feel it. I can feel it ticking when doing this.

 

It is important to follow these steps in THIS order. With the the "A" and "B" terminals shorted and the ignition "On", the IAC closes the IAC passage. The plug is removed from the IAC, so it can't receive a signal to move BEFORE the ignition is turned off or the paper clip removed.


Do you have the IAC or IAC housing grounded when you make this observation?


When you "bridged A and B at the ALDL", you put the ECM into the "diagnosis mode". As a part of the process of going into the diagnosis mode, the ECM activates various (most of) the relays and solenoids it has control over. The IAC is one of them. The IAC has no direct connection to the ALDL.


Amen!

RACE ON!!!

 

Broken!!!

You should not be able to rotate the pintle. The IAC motor is a rotating 'nut' and to move the shaft in and out the shaft must not rotate. There is small 'tab' that is easy to break.

 

thanks joby,
looks like the tab is broken then !!!!!!!!!!!

which wires should i see a voltage on in the connector????
and what should the voltage be when i ground A and B terminals,

thanks,
natt

 

http://members.shaw.ca/agent86/IAC%20Diagnosis.pdf

 

thats exactly what i was looking for,
thanks,
natt