RPM out of control

I've noticed when I turn my Bronco on the RPM is pretty high (sounds like I'm accelerating)... When I put the truck to drive the truck RPM level decreases and sounds fine. Only when my truck is idle (parked) the RPM goes up. How can I fix this problem? 

Yo,

I assume it is not carbureted..

So, 1st check is to look for a vacuum leak...

http://www.thedieselstop.com/faq/9497faq/maint/vra/images/a16145b.gif

See my leak test at

http://broncozone.com/topic/23994-90-58l-getting-continuous-code-33-and-running-code-44/?p=125535

Post number 20..

Miesk5, this is the picture of my engine. 

Before asking the forum, I was told that my idle air control valve was the problem. What role does this part play in my engine? 

Yo M,

Read about it at:

http://web.archive.org/web/20130912172111/http://www.oldfuelinjection.com/?p=39

by Ryan M.

Includes testing.

net

Location in an 85 302; bolted to the side of the throttle body, driver side near distributor.

Source: by Chris B (Blue, bronco boy)



Lastly, try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

http://broncozone.com/topic/14269-code-reader/?pid=74587&mode=threaded

Some basics;

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.

Run it around to heat the engine up and shift thru all gears including Reverse.

Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual & release clutch.

Then turn off engine, all accessories/lights (close driver's door) , etc.

Do KOEO test First

Post Code(s) here according to:

KOEO

&

KOER

GL!

Hello Supreme, would an idle air control valve make a difference or potential fix my problem?

Yo,

It could help.

Did you the test for codes?

This valve, which is sometimes referred to as a Throttle Air By-Pass valve, provides additional air to maintain the proper engine idle speed under varying conditions when commanded to do so by the Powertrain Control Module. This valve assembly may be directly mounted to the throttle body assembly or may be remote mounted to the intake manifold.

Source: by Ford fordinstallersupport

"Go under the hood, and disconnect the electrical connector to the IAC. If the engine begins to stubble or stalls the IAC is functional and does not need to be repaired. If the engine idle does not change you should remove the IAC for inspection.

The IAC can pass and still need repair, or it can fail and not need replacing. The plunger and internal spring can get clogged with dirt and oil. This will slow down the air flow and not allow the IAC to function properly. Remove the IAC and clean it. There are 2 halves to the IAC, and you can not buy just one half, but you can take it apart to clean it. But if the internal solenoid is faulty the IAC needs to be replaced." By Ryan M.

Miesk, I purchase a new IAC valve and it helped a little with the RPM. Where is the "There are 2 halves to the IAC, and you can not buy just one half" located?? The truck stalls a little when I'm accelerating. Like it doesn't get sufficient air. Can you guide me to trouble shoot... I'm very new to this... I know you made other recommendations but I dont know how to properly test. Therefore, I'm pretty much an idiot haha

Yo,

No problem on not knowing things.. been there too!!!

Iac is bolted to the side of the throttle body

pic by Travis L (kemicalburns)

Remove the IAC and clean it. There are 2 halves to the IAC, and you can not buy just one half because it it comes complete as Ryan shows.

You can take it apart to clean it. But if the internal solenoid is faulty the IAC needs to be replaced. by Ryan

IAC Removal & Cleaning Source: by Bobby (blue)

http://www.supermotors.org/getfile.php?id=146158&toggle=fullsize&f=.jpg

"...

http://web.archive.org/web/20140416125722im_/http://www.supermotors.org/getfile.php?id=146159&toggle=fullsize&f=.jpg

http://web.archive.org/web/20140416125722im_/http://www.supermotors.org/getfile.php?id=146160&toggle=fullsize&f=.jpg

"One thing I did different was used a dremel with the felt pad tip (came with the kit) to clean it. I could not get a tooth brush in there to clean it well enough. The dremel and felt pad worked AWESOME*** Might have to use it when cleaning other parts!" By Xris.

http://web.archive.org/web/20140416125723im_/http://www.supermotors.org/getfile.php?id=146161&toggle=fullsize&f=.jpg

The valve on the work bench is a spare I carry just in case but the one on the truck is the factory original I clean it every 6 months..."

; "...Disconnect negative battery cable. Disconnect the idle air control valve assembly connector from the wiring harness. Remove the two idle air control valve retaining bolts. Remove the idle air control valve (IAC valve) (9F715) and gasket. Installation: NOTE: If scraping is necessary, be careful not to damage sealing areas of idle air control valve or throttle body gasket surfaces, or drop material into throttle body, or intake manifold. Make sure that both throttle body and idle air control valve gasket surfaces are clean. Install gasket and idle air control valve on throttle body (9E926) or intake manifold surfaces. Install retaining screws. Tighten to 9.5 Nm (84 lb-in). Connect electrical connector for the idle air control valve. Reconnect negative battery cable..."

Source: by Ford

by JKossarides

"Okay, I really looked this IAC over on my 86 Bronco and the solenoid does come off by phillips screws as well as the 5/16 bolts on the throttle body so mine is in two parts. So unplug, unscrew and unbolt."

See if local parts store can scan for trouble codes for free. Or has one for sale within your price range.

Idle or Noise Problems & Troubleshooting; including HIGH IDLE Conditions; "...For high idle problems, try unplugging the IAC motor. If the idle drops, its usually due to an input signal to the computer which results in the computer raising the idle speed. If this is the case, look at all of the computer inputs to make sure everything is up to par. If the engine RPM does not drop when the IAC motor is disconnected, then either the IAC motor is not functioning properly, or, there is a vacuum leak in the engine. Stop the engine, remove the IAC motor and block off the passages. Restart the engine to see if there is any change in engine RPM. An idle speed higher than base idle specs indicates a vacuum leak. If the engine RPM is at base idle specs, then the IAC motor is bad. Resistance specs are 7-13 ohms. A good resistance reading does not necessarily mean that the IAC motor is good. Occasionally, an IAC motor will become weak, and will actually bypass too much air, causing a high idle condition even though everything else is operating properly..."

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