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Discussion Starter · #1 ·
my 99 SE has a very low idle. around 500 or less. i already cleaned out the IAC and the throttle body. i even unplugged the IAC and it has no effect which leaves me to believe it might be in wiring. i checked the voltage on the plug with the positive lead on the red wire and negative on the white i think it was. got around 28 volts AC. i got no ohm reading or DC reading.

i also have 2 codes p1507(IAC speed error) and p1504(IAC fault). because i unplugged it and it didnt stall i think the actual valve is fine. anyone else have any ideas? i also tired tapping on it and that didnt do anything.
 

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Cleaning doesnt always work. Sometimes replacement is needed. If the coil has gone bad, replacement is definately needed. IAC is a 40 Hz PWM modulated solenoid..... a variable duty cycle 12 V signal is applied to the IAC, so there is no way you could have measured 28 ACV. A DCV measurement will give a variable voltage (due to meter averaging) of under 12 V. An oscilloscope is better, allowing you to see the waveform the PCM is supplying to the IAC.
 

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Discussion Starter · #3 ·
okay thanks. today i got them checked again and i also got a p0402 egr valve which im assuming might be because of the issue with the IAC. so do you think a new valve will be the first thing to do?
 

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P0402 = excessive EGR flow detected. 99.9% chance the DPFE sensor has failed. VERY common Ford problem. Ford EGR valves themselves rarely fail. I assume the engine is running fine (no missing, good idle, etc). 402 can also be caused by a faulty EVR solenoid (leaking / sticking open), but that would result in a poorly running engine, especially at idle.
 

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im definatly going to try cleaning the EGR valve tomorrow.
There's nothing to clean really. If the car is idling smoothly, then the EGR is not sticking open. As Jeff K said, it's most likely the DPFE sensor. When you change the sensor check the attached hoses for rotting or breakage.
 

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There's nothing to clean really. If the car is idling smoothly, then the EGR is not sticking open. As Jeff K said, it's most likely the DPFE sensor. When you change the sensor check the attached hoses for rotting or breakage.

Agreed 100%. The problem is NOT the EGR valve, and cleaning it will do nothing.
 

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Discussion Starter · #8 · (Edited)
wow thats fucking awesome. broke the egr pipe trying to get the valve off.

idles around 1500 now. is it safe to go get the new pipe somewhere?
 
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