Hope someone can help my 97 4.6 with 99,000mi started missing 2 days ago,it was really bad when cold and got better when hot.Problem is the cel came on then but i wanted to remove chip to get scanned so i did and no light since but still acting the same.
The plugs are dbl plat. motorcraft with 10,000 mi,wires ars MSD superconductors 1yr old,cleaned MAF sensor 2 months ago,o2 sensors are less than 1yr old,I think the EGR is acting up but without cel on I am a little leary off tearing into the throttle body.
HOPE SOMEONE HAS AN IDEA,
THANX IN ADVANCE - RANDY

 

change out the dpfe...it,s causing a rich condition..thus the miss

 

I checked the voltage on the DPFE and found 5.06 ref voltage not running,and 0.77 signal voltage cold and stayed at 0.77 when hot.
Does this mean the sensor is bad?
Voltage hot should be 4.00 to 6.00 correct?

 

recheck your wires. They should be great but your symptoms point in that direction. simple resistance check should be easy and quick. I have replaced bad parts with new parts a lot only to have the new part be no good.

 

I dont know what you mean by recheck wires,is there a resistance value to check the DPFE?

 

something else i dont understand is when i unplug the sensor the voltage is 5.06 on ref and sig wires without engine running but key ON.

 

I meant your plug wires. They have been in service a year and although that is not very long it would still be worth a quick look. If you had a bad DPFE and were running rich your would have black exhaust.