Idle air control motor checked find but not working.

**Street Fighter** · 07-09-2015, 02:28 AM

I have been having problems with my idle on my 99 TA I posted some time ago about the problem and I am still trying to fix it myself after a dealer massed it up.I have checked the idle air motor, it is said to have to have 40 to 80 ohms when checked to be pass as ok, the Iac motor showed 48.7 ohms when checked, so it is suppose to be good ,but it is not moving in and out to set the idle like it is suppose to. I have checked the plug and there is voltage at all four plug ins on the wire going to the Iac motor. I don't see why this motor isn't working like it is suppose to. I can take it out and set it by hand and it will not move from that spot after days of driving.I know that the motor is suppose to move in and out to set the idle but it is not, two days ago it moved all the way open and the idle went to 1000 rpms in drive. so I know that it did move that one time. could it be bad even doe it was in the 40 to 80 ohms range to be good?

***SMWS6TA*** · 07-09-2015, 11:45 AM

My money it's shot and just needs replacing. I did one time took mine out and using carb cleaner, clean it up as best as I could. They tend to get a lot of oil buildup from the PCV being routed into the TB. Cleaning it is free (as long as you got the carb cleaner) might be worth a shot.

**pajeff02** · 07-09-2015, 04:55 PM

Expounding on what Scott suggested - carefully clean your entire throttle body while you are at it.

***SMWS6TA*** · 07-09-2015, 05:28 PM

yeah I should have said that. My stick TB at that time was clogged up bad. After clean up idle was much better.

**2002ssslp** · 07-09-2015, 08:23 PM

I feel it is sticking due to buildup over the years. Like everyone is telling you, clean the AIC motor and do your TB while you are at it. Good luck.

**Street Fighter** · 07-10-2015, 02:33 AM

I have cleaned it and the throttle, body they are so clean that they look new. but the iac motor just want work even doe it is within the 40-80 ohms to be good. I guess i'll be trying a new one and hope that it is the problem. 90.00 dollars is a lot to pay for nothing. wish me luck.

**pajeff02** · 07-10-2015, 03:09 AM

With the harness unplugged, check for continuity on the IAC between the Blue/White and Blue/Black wires. Then check for continuity between the Green/Black and Green/White wires. Each set of wires represents the control circuit for each of the two (2) coils on the stepper motor. If you find an open circuit, that coil is probably bad. If you want me to send you the diagnostic for the IAC, say the word. We are heading south this weekend though for the nostalgia drags and I will probably not be back on the site from home (where my books are located) until Sunday night.

**Street Fighter** · 07-10-2015, 11:36 AM

I checked the IAC motor like I said using my Hayes Manual it stated to check the IAC motor by checking the resistance of the motor, it said to check the D and C terminals on the motor than the B and A terminals and doing that I found 48.7 ohms on each set .which is suppose to be within the 40-80 ohms range to be seen as good I have checked the wiring plug that goes to the IAC motor and there is 10.45 volts on one plug and less on the others with the switch on.Is this what you are telling me to do or am I checking the wiring wrong by grounding the meter neg post and checking the plug terminals with the hot post?

***SMWS6TA*** · 07-10-2015, 11:51 AM

Simple test.....do you know another person that has a LS1?

Borrow their IAC and swap it in for yours. This will save you a ton of time and guessing. I just did this with my buddys car last night.

His idle was way down with the ac on even after a recent dyno session. He thought it was the IAC hole or IAC motor. Turned out to be all he needed was the airlid tray mod.

He wasn't getting enough air from the filter. I did it on a whim because when we took the air lid off it would idle and with it on it wouldn't (With the ac) even with my IAC motor. It idles much better now with/out ac.

**pajeff02** · 07-11-2015, 03:48 AM

Same test - you just checked ohms rather than continuity. If the circuit to one coil or the other were bad it would read as open.

**Street Fighter** · 07-23-2015, 01:58 AM

After checking good I went own and replaced the motor any way hoping that it may have been getting stuck, but there was no difference, now I know that it's not in the motor it's something that the tech did to my car when he installed the new computer in my car,I have used the IAC motor pulled out far enough to block off the air passage hole coming in to the throttle body and unplugged the IAC motor so it will not move away from the air hole in the throttle body. I have now Idled the engine with the small screw located in the throttle body, it idles at 600 rpms at start up and goes to about 800 rpms after heating up. so far this is working find. Will this cause any kind of problems, the cars runs great still, but I just wanted to know.

**pajeff02** · 07-23-2015, 03:29 AM

Disconnect your battery and pull the plugs on your PCM. Check the pins to ensure that they are not bent, broke off or corroded. If you want to check continuity between the PCM and IAC, let me know and I'll post the PCM pinouts.

**Street Fighter** · 07-31-2015, 12:39 AM

I you don't mind please post the PCM pinouts so I can check them against those of my IAC.

**pajeff02** · 07-31-2015, 02:51 PM

On the PCM harness - Connector 2 (RED) it is as follows:

A - Lt. Green/Black is Pin 77

B - Lt. Green/White is Pin 76

C - Lt. Blue/Black is Pin 78

D - Lt. Blue/White is Pin 79