IAC Results

slow5.0gt · Jul 6, 2007

I still cant get my mustang to idle, i waited till i got another IAC slapped it on set the idle with the iac d/c and the spout set it at 900 rpm perfect no bobbing nothing. turn off engine pluged the iac and the spout back in. turned the car on, idles like crap around 500 to 300 jumping up and down and then engine dies after about 2 mins.
What the hell right? reset computer remove iac and spout, turn car on set this time the idle to the highest it will let me go which is about 1500 turn off car and plug in iac and spout. Same exact result 500-300 jumping and then dying engine

Now everytime i reset the computer,d/c iac and spout and try to start it up with the last settings on the throttle body screw i have to make sure that the throttle screw is turned to the max open because if I do not it will just crank over till i give it gas to start.

Even when I set the screw to any idle i want whter it be 900 or 1300 without even putting in the iac or spout as soon as the car gets turned off and i try and crank it immediately back over it will sputter till i give it gas or until the throttle screw is opened to the max

Im not sure if im even susposed to do that crapola but that was me testing it even if the computer isnt reset shouldnt it remember that idle that was set on the throttle screw? right after it was turned off and turned back on.

I have a thoguht since this is the replacment engine i got from the old one getting hydro locked this might be the wrong computer for it since we just dropped in the engine. But would that even cause any of the problems im talking about here?

jrichker · Jul 6, 2007

Are you stil running the E cam?

Your mechanical base idle speed is too high. The computer wants to idle the car at 650-725 RPM and you have it set way above that.

Copied from the "Surging Idle Checklist

First of all, the idle needs to be adjusted to where the speed is at or below 600 RPM with the IAC disconnected. Then the electrical signal through the IAC can vary the airflow through it under computer control. Remember that the IAC can only add air to increase the base idle speed set by the mechanical adjustment. The 600 RPM base idle speed is what you have after the mechanical adjustment. The IAC increases that speed by supplying more air under computer control to raise the RPMs to 650-725 RPMs

Remember that changing the mechanical idle speed adjustment changes the TPS setting too.

This isn't the method Ford uses, but it does work. Do not attempt to set the idle speed until you have fixed all the codes and are sure that there are no vacuum leaks. Warm the engine up to operating temperature, place the transmission in neutral, and set the parking brake. Turn off lights, A/C, all unnecessary electrical loads. Disconnect the IAC electrical connector. Note the engine RPM: use the mechanical adjustment screw under the throttle body to raise or lower the RPM until you get the 600 RPM mark +/- 25 RPM. When you are done, reconnect the IAC electrical connector. Changing the mechanical adjustment changes the TPS, so you will need to set it.

An engine that whose idle speed cannot be set at 600 RPM with the IAC disconnected has mechanical problems. Vacuum leaks are the #1 suspect in this case. An extreme cam can make the 600 RPM set point difficult to set. Contact your cam supplier or manufacturer to get information on idle speed and quality.

E cams are supposed to have good idle characteristics, so you may have some other problems.

slow5.0gt · Jul 6, 2007

yea I still have the e-cam i was taught differently to set the base idle but even if i set it around 600 it does the same thing. Its like ic an get the car to idle all good without the iac plugged in at all but once its plugged in the computer goes all haywire.

Or better yet after the car is turned off, its like it loses its settings i dont get it.

jrichker · Jul 6, 2007

Dump the codes and look for code 15. It is the code that has to do with the computer's ability to hold "learned settings".

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

See http://www.troublecodes.net/Ford/

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

89 through 95 cars have a working Check Engine light. Watch it instead of a test lamp.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/pc-7208-90-equus-digital-ford-code-reader-3145.aspx – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

IF you haven't already carefully gone through the Surging Idle Checklist, I encourage you to do so.
See "Surging Idle Checklist for help with all your idle problems. The first two posts contain all the updates to the fixes. I continue to update it as more people post fixes or ask questions.

slow5.0gt · Jul 6, 2007

Yea i ordered a code reader just waiting on it to come in

fox-gt · Jul 6, 2007

I had all kinds of problems getting a good idle with my e303 cam. I tried messing around with the idle screw but it either idled way to high or way to low. Installing an IAC Adjuster made mine drivable. I get an idle of around 800 to 900 without wanting to die.

slow5.0gt · Jul 6, 2007

iac adjuster? not familar with that too well. its that plate you put inbetween the iac and the throttle body correct?

fox-gt · Jul 6, 2007

slow5.0gt said:
iac adjuster? not familar with that too well. its that plate you put inbetween the iac and the throttle body correct?

Correct.

Pic

http://www.latemodelrestoration.com/iwwida.pvx?;item?item_no=LRS-9939A 1&comp=LRS

I had mine checked for vacuum leaks, computer throws no codes. I searched for months on many different forums on the issue. From everything I have read, that cam just has a rough idle, especially with AODs

slow5.0gt · Jul 6, 2007

Another thing, if i plug in the IAC while im setting the throttle body it will do one of the 2. 1 the idle will go from being steady to being really jumpy and ****ty then die. or number 2. it will increase the rpms like its susposed to.

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