hey shorod-try this one

[rodfoster]

hi my mom's 99 taurus se 3.0 duratec? plain engine, vin code u i think.anyways p1504 iac circuit malfunction-haynes book says it should be within certain spec for resistance-i am below this spec. it was like two months ago i checked it-but i'm sure it was 7 or 8 ohms.should i replace it? car does have a cold start issue-idles high, then stalls (sometimes). i was going to try to do a fuel pressure test, but either i need to remove alternator or i need a 90 degree adapter for pressure gauge-do you think that is available? you seem to be the man on this stuff. thanks in advance

[shorod]

The "plain engine" and I believe 8th VIN of U is the "Vulcan" 12V engine. The Duratech is the 24V engine, but I'm not sure of the VIN.

The factory service manual hints that a P1504 indicates that the IAC motor is likely shorted to ground. If you measured lower than specified resistance, that is an indication that you may in fact have a shorted IAC to ground.

There are a few ways you can check the operation of the IAC motor. You can try unplugging it and seeing if that has any effect on the way the car starts, idles, and/or runs. If it does not, that is a good indication the motor is shot.

You can also turn on the defroster or A/C (if the ambient temperature is above freezing) and see if that causes the engine to speed up or bog. If the engine bogs, you probably have a bad IAC.

The engine should also speed up slightly if you turn the power steering all the way to lock and hold it there for a couple of seconds. You don't want to hold the steering at either of the locks for more than 5 seconds or so as that could cause damage to the power steering pump. If the engine bogs or stalls, you probably have a bad IAC motor.

As for checking the fuel pressure, I'm not sure on that particular engine if it requires something special, but I would be surprised if it did. Maybe someone else on this forum has checked the fuel pressure on the same engine and has some pointers for you.

-Rod

[rodfoster]

thanks alot-you are the man!! sorry about my lack of info-mom's car and i try to stay away from it as much as possible.i drive gm mainly-but i gotta admit this is a nice car. runs really quiet,a few things don't work-cruise-ac-temp control is messed up, lots of posts about temp control.do you know of any tests the backyard guy can do for the cruise?i think it may use a servo-or maybe not.haynes book does not discuss this. thanks

[shorod]

There are some electrical tests you could start with on the cruise. I don't have the wiring diagrams in front of me.

-Rod

[shorod]

How comfortable are you with reading wiring diagrams? I can send you a PDF version of the wiring diagrams. If you'd like the diagrams, send me a private message with your request and an e-mail address that can accept PDF attachments.

If you aren't comfortable reading the diagrams, then I'll attempt to outline a few items to check.

In the instrument panel fuse box there are a couple of fuses to check, fuse 6 (15 A) that should be hot in run and fuse 28 (15 A) which should be hot at all times. Both of these fuses feed power to the speed control module, which includes the servo.

Also, check to see if the horn works. The cruise is set up to de-activate if the horn is honked. If the horn switch is shorted to ground, someone may have removed the horn relay rather than fix the switch, therefore preventing the cruise from engaging. When the relay is installed, this line floats high through the horn relay coil and fuse 19 (15 A) in the engine compartment fuse/relay panel.

-Rod