Idle Issues

Dec 9, 2015
38
1
8
38
Louisiana
#1
hi all looking for a little help on my issue here’s a little background on my car I recently purchased a 04 gt 4.6 has all bolt on mods with a catless exhaust system and a73mm BBK throttle body just a few days ago I started to experience idle problems when I get in the car in the morning start it up and when the car starts and still in warm up mode car runs fine but when it drops down out of warm up mode the idle will surge from 500 to a 1000 and then drop down to where it might die sometimes it does die and it repeats this process till I put it in gear and drive it for a few minutes then the car runs normal for the rest of the time until I turn it off and restart it then it repeats the same symptoms again things I have done to try and fix it had a check engine light on so I had codes scanned and it was 02 sensors codes went to changed the 02 sensors found that the back two sensors the wires were cut off looks like it was cut on the count it wouldn’t reach the plugs on the harness so I changed all 4 sensors and bought some extensions for the back two sensors and the code went away for one day then came right back on replaced IAC valve in attempt to try and fix the idle and it did the car ran great for one day the next day get in it crank it up and the same exact thing so I cleaned the air flow sensor no changed checked vacuum lines only visually checked and it appears no hoses are cracked /broken tomorrow I’m going to make sure intake and headers are tight and throttle body flap closes and don’t hang up Kinda loss in it now can someone maybe point me in a direction are tell me if I’m overlooking something I would greatly appreciate any info on my problem thanks
 
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Dec 9, 2015
38
1
8
38
Louisiana
#3
I have not and will do first thing at day break and thanks for the checklist going to start going through it and check everything as stated will get back to you and let y’all no what I find
 
Dec 9, 2015
38
1
8
38
Louisiana
#4
90CC044F-275E-488C-B7EF-1F10AF95C14C.jpeg
9CA437F7-D60C-496A-B0C0-44B04156D6F3.jpeg
Think I found the problem but I’m not sure what the part is called can someone identify the part has two vacuum lines hook to it and it’s on the backside in the pic best I can get bring it is so close to the firewall
 

wmburns

SN Certified Technician
Aug 14, 2009
4,543
277
154
Houston Texas
#5
The part in the picture is called the DPFE sensor. It purpose is the measure the flow of EGR gases flowing back into the intake. The lines are not vacuum lines per se. The lines carry exhaust gases.
 

Neuron

Mustang Master
Nov 6, 2016
623
125
83
68
#6
The part in the picture is called the DPFE sensor. It purpose is the measure the flow of EGR gases flowing back into the intake. The lines are not vacuum lines per se. The lines carry exhaust gases.
Those two rubber lines carry exhaust gases to the plastic DPFE Sensor? I would think the whole thing including the lines would melt. I thought the lines were vacuum to modulate the sensor and the exhaust gases.
 

wmburns

SN Certified Technician
Aug 14, 2009
4,543
277
154
Houston Texas
#7
Those two rubber lines carry exhaust gases to the plastic DPFE Sensor? I would think the whole thing including the lines would melt. I thought the lines were vacuum to modulate the sensor and the exhaust gases.
Yes it's connected across a small restriction in EGR line. While it is connected to exhaust gas no gas actually flows through the DPFE sensor. But if the factory lines are installed you will notice just how much beefier the flexible than a normal vacuum line.

Note. DPFE stands for Differential Pressure Feedback EGR. It works by comparing the pressure difference between the two ports.
 

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