my first Ford successful repair!

well i've been messing around off and on with my mom's car 99 taurus 3.0 vulcan? (pushrod engine) and a while ago Shorod gave me some tips and of course after reading many threads here i eliminated p1504 (IAC something or another) so i tested the IAC valve-needed 6 to 12 ohms. at first i had meter reading under 20k not 200 so it kept saying 3.95 on the old IAC and 0.01 on the junkyard one. What am i doing wrong? i got thinking about it and realized that you need to be close to the value you expect to get. so i guess the old IAC was like 3,950 ohms? i don't know, but once i figured out how to read the meter the junkyard IAC was 10.5 ohms!! put it on erased the code and p1504 hasn't been back. now-p0401 and i won't ask for suggestions because there are so many out there! however since i put the IAC on p0401 hasn't been back-seems too good to be true

Congratulations on the successful repair!

If you had your manual ranging multimeter set on the 20 kohm scale and were getting a reading of 3.95, yes, that would indicate 3.95 kohm or 3,950 ohms.

So prior to replacing the IAC you also started seeing a P0401 code, but with the replacement IAC that code hasn't come back either?

When you replaced the IAC, did you spray out the throttle body with cleaner? Maybe you managed to clean out the EGR passages while you were at it, helping with the P0401 code. Or, maybe you managed to reposition one of the EGR vacuum lines to temporarily seal a vacuum leak.

-Rod

actually i didn't do anything at all, i just erased the codes and p0401 hasn't come back yet. i see where you're going with this-IAC and 0401 are not realated so why should it go out.i think i was hoping it was that "cascade effect" i read about-not likely. so, last night i had a new dpfe and hooked it up-no change. p0401 is still not coming back, but the car idles high, when you fisrt start it 1500-2000 rpm maybe it will come down to 900-1000 if i am lucky. i thought the computer was compensating for low egr and that was the idle issue-also she claims in the winter on snowy roads that at stop signs the car will want to take her right through the intersection! even when i drove it it is about 1500 at most stop signs. i wonder if i should test fuel pressure regulator for high idle? any help would be great, also what cleaner should i buy for throttle body? thanks alot

If the idle is smooth, I don't think the EGR/DPFE will be the issue. I'd be more inclined to think you have a problem with the IAC or Throttle Position Sensor (TPS).

So even though you measured your IAC to be out of spec and the one from the junkyard to be in spec, you didn't change it out?

Does the high idle seem like more of an issue in cold weather? Have you measured the resistance of the Coolant Temperature Sensor (make sure you check the sensor and not the sender) to see if it correlates to coolant temperature? This check is best done after the car has been sitting overnight so the engine temp is pretty much the same as the ambient temp.

I've been very pleased with the performance of the STP Throttle Body Cleaner. I've been able to find it at Autozone.

-Rod

yes i did change the IAC with used one-10.5 ohms. the ambient temp does not seem to matter either way. i just drove it back to her house and it is odd when you take the car out of drive to park or neutral the rpms shoot up by at least 200 usually more than that. even at engine norm temp it idles about 900-1000. the temp senders aren't there two side by side one for ecm one for gauge?are there any others? i would want to test ecm one, right? sorry for all the questions, i work parts dept at a tractor dealership! local car dealers here don't want to tell you anything

You're right, there are two temperature devices, the sensor (for the ECM) and the sender (for the gauge). The sensor for the ECM is the one that the ECM uses to modify the idle speed, timing, etc. and therefore the one you will want to check. You can use your ohmmeter to check the TPS sensor for linearity as well which would be another good check.

-Rod

The P0401 will return soon. The high idle may be due to a small vacuum leak which allows the PCM to introduce mnore fuel to the engine, raising the idle. Did you replace the IAC gasket with a nrw one? If not, it is possible the gasket has a tear in it causing a vacuum leak.