You can type here any text you want

What Causes High IAC Readings

Welcome!

By registering with us, you'll be able to discuss, share and private message with other members of our community.

SignUp Now!
J

~JM~

Wrinkled Member
Joined
Oct 31, 2007
Messages
3,227
When I first hooked up my Scanmaster my IAC & TPS were within acceptable ranges so I didn't mess with it. Yesterday I noticed my IAC readings were far above the 20-25 range. I tried to readjust it with the screw & am not able to bring the readings down any lower. I can raise the numbers but not lower them.

Would this be an indication that the IAC has gone bad or has stuck & cannot move any longer. I found the IAC to be bound up once before. I was able to lube it up & get it to turn, but I don't know if maybe it is stuck again.

Thanks
~JM~
 
Check for any sort of vacuum leak on the intake manifold, after the throttle body.
 
steper motor might be stuck vacume leak any were could cause that and how did you go by adjusting iac did you down tune tps to .32 befor
 
I dont think it could be a vacume leak. a vacume leak will give a low iac count.
Iac adjustments copied from GNTTYPE.ORG

The ECM controls idle rpm with the IAC (idle air control) valve. The idle rpm is programmed into the PROM. To increase idle rpm the ECM moves the IAC valve out allowing more air to pass by the throttle plate. To decrease rpm it moves the IAC valve in to reduce air past the throttle plate. A scan tool will read the ECM commands to the IAC valve in counts. Higher the counts the more the air is being allowed to pass the throttle plate (higher idle). Lower the counts the less the air is being allowed to pass the throttle plate (lower idle).
  1. Warm the engine to normal operating temperature. This is important ... the car needs to be in closed loop.

  2. Connect scan tool. Verify it's in closed loop.

  3. Put the car in park and wait a couple seconds for it to settle into a regular idle.

  4. Look at the IAC counts (# and not % in TurboLink™)

  5. If the IAC counts are between 10-40, then it's pretty close. Otherwise, do the following adjustment procedure, with a target number of around 20-25 counts.

  6. The Minimum Air adjustment screw is on the dirver's side of the throttle body on the throttle linkage arm (often times misunderstood as the "idle adjustment screw". Pull off the gray rubber cable protecting the screw head.

  7. Turn the screw in VERY small amounts (1/4 turn or so) to adjust the Minimum Air setting. Turning it counter clockwise closes the throttle blade and will normally raise the IAC counts. Turning it clockwise opens the throttle blade and will normally lower IAC counts.

  8. Carefully monitor the IAC counts while making small adjustments to the Minimum Air setting screw. Be sure to allow the car to "settle" a bit after each adjustment a couple of seconds.

  9. Once you have IAC counts adjusted to within your target range, adjust the TPS as described HERE.
 
Well I tried working on it again this afternoon. I pulled the IAC & checked to make sure it wasn't froze up. Everything seems to move properly. I threaded the pintle all the way in before I threaded the IAC back to snug. Reconnected & fired it up. It actually started working properly & maintaining a good number so I dialed it in a little bit & thought I had it. Went to restart & this time the count is near 100. With key on & engine off the IAC reads 140 every time, but once you start it starts heading for the high end of the scale.

Should I just replace the damn part & see if that fixes it. Hate to buy something just to see if it will work or not.

Thanks
~JM~
 
Do you have a buddy with a TR close by? Maybe you could switch with someone just to test.
 
I'm about 20 miles west of Portland off of I-30. Did you check the IAC passages to make sure they are clean? If there is any blockage the IAC reading will be high. I may have another IAC valve laying around here. If you want to make the trip out here let me know. I'll see if I have one.
 
I'm having similar problems. I had a small stumble and adjusted the adjustment screw on the throttlebody. I also adjusted the T.P.S . My I.A.C was #00 before the adjustment.All #'s were perfect after adjustments and no more stumble then shut the car off and restarted then I noticed a high idle. I tried to readjust many times with the same result.Each time I shut the car off the idle would race.I just ordered a new T.P.S and a new I.A.C. Bought both parts for under $ 50 buckss At least you have people close to help. I'm on my own in S.I N.Y.C......
 
mikestertwo said:
I'm about 20 miles west of Portland off of I-30. Did you check the IAC passages to make sure they are clean? If there is any blockage the IAC reading will be high. I may have another IAC valve laying around here. If you want to make the trip out here let me know. I'll see if I have one.
Click to expand...

Mikestertwo,

Please check your PM's

Thank you
~JM~
 
Wow. This post is 10 years old. . Car is running better than my new cars
 

Attachments

  • 20220909_093109.jpg
    20220909_093109.jpg
    318.7 KB · Views: 46
You must log in or register to reply here.

Similar threads

tt455
IAC at 00 next step
2
29
3K
SCOOBY DOO
SCOOBY DOO
Turbo6BK
Stuttering after warmed up and driving
7
622
Turbo6BK
Turbo6BK
NoVA_87_GN
Scanmaster G readings
2
33
4K
1KWIKSIX
1KWIKSIX
J
better weather plans for your TB
0
229
jlat
J
M
A/C Blowing Opposite Way(?)
3
408
xlr8ngn
X

Online statistics

Members online
26
Guests online
344
Total visitors
370
Totals may include hidden visitors.

Newest members

Stay Connected

Back
Top