Min. Idle speed adj.

[Achilles]

I'm reading my shop manual about the min. idle speed adjustment and I'm a little confused over the terminology.

1) With the IAC motor connected, ground the diagnostic lead.

 

[Achilles]

Sorry, I pushd the wrong button.


Anyway..... What lead are they refering?


I read somewhere that you put a jumper wire between the A & B terminals on the IAC motor. If I understand this correctly, are they implying that I use 2 pieces of wire to connect the IAC harness to the IAC motor from the A & B terminals and then touch those two leads together?

I want to check this out first from somebody that has a clear understanding of this before I go touching wires to other wires.

 

[jimmers]

Sorry, I pushd the wrong button.


Anyway..... What lead are they refering?


I read somewhere that you put a jumper wire between the A & B terminals on the IAC motor. If I understand this correctly, are they implying that I use 2 pieces of wire to connect the IAC harness to the IAC motor from the A & B terminals and then touch those two leads together?

I want to check this out first from somebody that has a clear understanding of this before I go touching wires to other wires.

On my 90 the plug is under the drivers side kick panel. Use one piece of wire to ground out terminals A and B. The fan should turn on if you did it correctly. I dont know if its the same on a 83 but im sure someone will correct me if im wrong.

 

[speedmaster4]

sit in the drivers seat
put your hand on your right knee
point fingers forward, u are touching aldl diagnostic lead connector.
connector could have a slip-on black plastic cover--most dont have it
upper row--two terminals furthest to right are a&b

 

[Jeb]

Here are a couple of links you may find informative...

http://www.geocities.com/jgkov/TPSService.html

http://www.geocities.com/jgkov/TPSService.html

 

[Vettefan87]

sit in the drivers seat
put your hand on your right knee
point fingers forward, u are touching aldl diagnostic lead connector.
connector could have a slip-on black plastic cover--most dont have it
upper row--two terminals furthest to right are a&b

What he is referring to is the IAC I think. Which is under the hood, the diagnostic port is inside the car to check trouble codes. Is that what you are talking about or did I misread something?

 

[Achilles]

Here are a couple of links you may find informative...

http://www.geocities.com/jgkov/TPSService.html

http://www.geocities.com/jgkov/TPSService.html

This is where I saw one of the proceedures, except it was

http://www.geocities.com/jgkov/IACService.html

I read this and the instructions in the repair manual over & over and just was not sure what it was explaining. I think my confusion came from seeing a dia. in the repair manual that shows A, B, C & D terminals on the IAC valve & could not make sense of the whole thing. I think I know now that the terminals are @ the plug under the drivers dash. Has anyone ever done this test?

Thanks guys!

 

[tigmaned]

yes you take a paper clip, open it up to a C shape and put one end in A and other end in B (top two wholes) slot in the ALDL which is under your dash on the carpet panel. then set IAC as in the attachment.

 

[speedmaster4]

almost all electrical connectors on the c4 have the individual pins identified by letters or numbers cast onto the plastic...diagrams in the service manual will show these id's pictorily, but they are never (that i have seen) refered to in text.

IAC motor fries(magic smoke departs) if u apply 12V to it...several other control circuits are similar---dont try to power up anything unless u are really sure of what u r doin

 

[Achilles]

yes you take a paper clip, open it up to a C shape and put one end in A and other end in B (top two wholes) slot in the ALDL which is under your dash on the carpet panel. then set IAC as in the attachment.

Thanks, I also found a related post from back in June that had a link to the correct procedure. This helps a lot and hopefully this will take care of my idling issues. I think I've tested everything else and they check out ok. If this fails, then I think it's my ECM gone bad.

 

[speedmaster4]

could be a bad IAC motor...new one is about $60..used one from jy is ez find-gm used same part in almost everything 85-92..visually compare end of pintle of replacemnet part

just had to r&r an iac--at idle or in gear at a stop sign,engine would ocassionally "surge"....what duz ur car do?

 

[Achilles]

just had to r&r an iac--at idle or in gear at a stop sign,engine would ocassionally "surge"....what duz ur car do?

"Lopes" & "surges" at start-up. Not quite as bad when it's warmed up. More like just a rough idle when warm. I checked the ohm's reading for my IAC for the req'd min. 20 ohm 2 the teminals A & B, C & D. Got that easily with a 40+ reading. So, I'm assuming the IAC is good.

Since I foolishly half-assed adjusted the idle speed screw, now the car races up to 2300 rpm at start-up before settling down.

 

[speedmaster4]

sounds a bunch like the problem i just had...problem 95% disapeared with change of IAC, took about an half hour to go completely 'normal'--ecm must have "learned" old IAC i guess....still have one-time 'stumble' when ecm switches from open to closed loop but that is normal

 

[Achilles]

Well, things are improving!

First, I could not get the idle RPMs down below 1300 after grounding the A & B diag. terminals, seating the IAC and disconecting the IAC cable. Just about had the idle screw fall to the floor.

So, I checked my TPS. It was set at .29 volts...way off! Reset TPS to .54 then restarted the whole procedure over again.

Long story short, I could never get the car to idle down to 450 RPM before it would stall. Lowest was about 550. But the car is alot better than before. Still a little bit rough on the idle, and doesn't hunt nearly as much. Vacuum gauge reads steady, but low, indicating late ignition timing. My timing is dead on @ 6 btc. So could be worn timing gears....dunno.

I think I'll go ahead and replace the IAC valve anyway and see what that does before I tear into the motor to replace the gear set. I'm just glad I made some progress. Thanks to everyone for their assistance.

 

[speedmaster4]

did u disconnect the ' set timing connector' ?

 

[Achilles]

did u disconnect the ' set timing connector' ?

Yes I did. Today, I reset the IAC and TPS again. Then I disconnected the battery cables and reattached the battery and took the car for about a 15 min. drive to allow it to reset itself. This is the best I've ever had this car running. I still wouldn't say it's perfect. It still has just a minor surge at idle, but only once in awhile. It's 90% better than it was, so I'm gonna leave it alone for now.