89 5.0L high idle after cleaning iac and throttle body

89 5.0L EFI. I pulled the iac and cleaned with carb cleaner, I also cleaned the throttle body plates but did not remove it. After reinstalling everything the idle was very high, like 2,000 in Park and 1,500 in gear. So I disconnected battery for 5 minutes then let it idle for about 15. Now it has come down some but it’s still too high, in gear it’s at 1,000 and in park or neutral it’s at 1,500. Any ideas?

I just got done fighting this issue on my Bronco. And I caused the issue the exact same way. The Throttle Body was just too clean.  )   To fix the issue Check your base idle setting, You can do this by pulling the connector going to the IAC and reading the revs on the tach. 500-750rps is about what you want. If the revs are too high check your base idle *****. The ***** is 5/16 and easy to turn.

IF you have the base idle setting at 600rpm but once you plug the IAC in the RPMs jump to 1200rpm. :: Remove the battery cable to reset the computer.

IF the idle sped is still to high check the TPS and make sure the voltage is below .998v but above .985v. I have my TPS set at .995 and don't have any issues.

IF you have correct TPS voltage and you base idle ***** is back'd out all the way you can cover the holes on the upper and lower butterflies. I used painters tape and I still have the tape in the correct spot, the engine hasn't sucked in my tape. I would also recommend ducting foil with the sticky back to cover the holes, just make sure the tape in on as flat as possible to prevent it becoming sucked into the engine. If requested I can provide a link to some quality stuff.

If none of that helps, repalce the IAC with a new one and re-set the computer.

Hope that helps. If you have more questions ask away.

Yo,

High idle with no applicable codes is usually caused by:
Vacuum leaks. See my leak test in post #20 @ http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/?p=125535

Excerpts;

Normal Engine Vacuum at Idle is 15-22 in-Hg for EFI Broncos;
Borrow or purchase a vacuum gauge and read this Vacuum Gauge Diagnosis @ http://www.diesel-da...tj/stj30013.htm
Similar to other EFI years.

One way to do a quick check is to grab a vacuum gauge. Bring the engine to normal operating temperature. Connect gauge to the intake manifold tee. BEWARE OF FAN, BELT, PULLEYS & HIT ENGINE. 
The vacuum gauge should read between 15 and 22 in-Hg depending upon the engine condition and the altitude at which the test is performed. SUBTRACT ONE INCH FROM THE SPECIFIED READING FOR EVERY 1,000 FEET OF ELEVATION ABOVE SEA LEVEL.
The reading should be quite steady. .

When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure.

When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.