High Idle
Thread Starter
Racer
Joined: Aug 2007
Posts: 305
Likes: 1
From: DRAYTON VALLEY ALBERTA
High Idle
I have a high idle problem. I did do the IAC configuration, by grounding the ALDL with KOEO. When I unplug the EST timing conector with the ALDL grounded and my throttle plates completely closed, the motor dies instantly. So I turned the screw on my throttle body to get about 450-550 RPM. Then I plugged the IAC back in, and the EST, and ungrounded the ALDL. As soon as I fire up it idles at 1300 then as I use the happy pedal, it just gets higher up to about 2200 RPM. And thats where it sits while in PARK/NEUTRAL. When Im in gear it even sits at 900 RPM. Thats too high. Any suggestions. With It dying that quick during my configuration, Im assuming its not a vac leak.
Melting Slicks
Joined: Aug 2003
Posts: 3,403
Likes: 398
From: Lakeville MI
Back off on the throttle stop adjusment until it can maintain the commanded idle speed in gear with both A/C on and A/C off.
Or go back and set the min-air again, but this time with the EST connected, and just set the rpm close (within 50-100 rpm) to your commanded idle (600 rpm or so, depending upon your tune) instead of 450 rpm. This will bring the IAC counts down to approx. 10-20 counts for a normal idle in gear.
Verify A/C on and A/C off can maintain idle at the desired rpm in gear.
With heads and cam, it needs too much air to idle at 450 rpm with only 6 degrees advance to run normally with 26-30 degrees advance with the EST connected.
Or go back and set the min-air again, but this time with the EST connected, and just set the rpm close (within 50-100 rpm) to your commanded idle (600 rpm or so, depending upon your tune) instead of 450 rpm. This will bring the IAC counts down to approx. 10-20 counts for a normal idle in gear.
Verify A/C on and A/C off can maintain idle at the desired rpm in gear.
With heads and cam, it needs too much air to idle at 450 rpm with only 6 degrees advance to run normally with 26-30 degrees advance with the EST connected.
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Leave the TB screw alone, these cars should never need them to be touched.
Check for a vacum leak and then if that clears ok I'd investigate your TPS sensor. Do you have an analog multi meter handy? Get a TPS test harness or stick a couple needles in (I think the top two wires) and watch the multi meter. Slowly open the throttle with your hand (engine off, key on) and the needle on the multimeter should sweep smoothly from ~0.54V towards 5.0V. You probably won't hit 5.0V, but its should be heading that way. If you see the needle bouncing as you open the TPS, replace the TPS. If you see it starting way over 0.54V, adjust the TPS and re-test. You can use a digital multimeter if you want to, but an analog one is easier to watch for bouncing.
Check for a vacum leak and then if that clears ok I'd investigate your TPS sensor. Do you have an analog multi meter handy? Get a TPS test harness or stick a couple needles in (I think the top two wires) and watch the multi meter. Slowly open the throttle with your hand (engine off, key on) and the needle on the multimeter should sweep smoothly from ~0.54V towards 5.0V. You probably won't hit 5.0V, but its should be heading that way. If you see the needle bouncing as you open the TPS, replace the TPS. If you see it starting way over 0.54V, adjust the TPS and re-test. You can use a digital multimeter if you want to, but an analog one is easier to watch for bouncing.
Team Owner
Joined: Sep 2003
Posts: 20,179
Likes: 673
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Another option;
Check to see if the IAC is functioning by removing the valve and then pluging in the connector. turn the ignition key to on and observe the pintel operation. If the valve is functioning properly, it will fully extend and eject the pintel. So you might want to place the valve in a plastic bag to recover the parts.
I had a valve go bad recently and IAC motor was not functioning. The pintel would move a little bit and then stop. Replacing the valve was the fix.
Check to see if the IAC is functioning by removing the valve and then pluging in the connector. turn the ignition key to on and observe the pintel operation. If the valve is functioning properly, it will fully extend and eject the pintel. So you might want to place the valve in a plastic bag to recover the parts.
I had a valve go bad recently and IAC motor was not functioning. The pintel would move a little bit and then stop. Replacing the valve was the fix.
Thread Starter
Racer
Joined: Aug 2007
Posts: 305
Likes: 1
From: DRAYTON VALLEY ALBERTA
If you read my signature it says I have a FIRST intake. The reason why I have a high idle is my throttle plate is not returning to the stop screw.I think somthing is wrong with the bushing in the throttle body. I found it today. Thanks for all the imput guys. If I hadnt f had you I would not have been checking my IAC for the fourth time and found it.
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
87,
Been there, done that! I just got through replacing the throttle body on my 88 for the very same reason. The throttle blades were hanging exactly as you describe. I could push the throttle arm and get it back to idle. Also the worn throttle shaft makes for a vacuum leak that confuses the EFI system even more.
There is a company at Xtremefi.com that rebuilds them and bores them to 52MM in the process. They go back together with a ball bearing instead of a bushing.
I got one of their units and my car is now running better than it has in years. Mine was so bad the cruise control was even surging due to the mechanical resistance.
Out of curiosity, is yours a stick shift car? Is it a high mileage car? My car is both. It is a stick, plus it has almost 130,000 miles. I think the stick shift cars wear out the throttle shaft quicker because you are opening and closing the throttle much more often than with an automatic.
Good luck with it.
Doc
Been there, done that! I just got through replacing the throttle body on my 88 for the very same reason. The throttle blades were hanging exactly as you describe. I could push the throttle arm and get it back to idle. Also the worn throttle shaft makes for a vacuum leak that confuses the EFI system even more.
There is a company at Xtremefi.com that rebuilds them and bores them to 52MM in the process. They go back together with a ball bearing instead of a bushing.
I got one of their units and my car is now running better than it has in years. Mine was so bad the cruise control was even surging due to the mechanical resistance.
Out of curiosity, is yours a stick shift car? Is it a high mileage car? My car is both. It is a stick, plus it has almost 130,000 miles. I think the stick shift cars wear out the throttle shaft quicker because you are opening and closing the throttle much more often than with an automatic.
Good luck with it.
Doc
