Hi guys,
After more than 6 months of trouble and a change of motor I really don’t know what else to do.
Any help will be appreciated.
So here it is, I have a 1997 expedition, 4.6, 4x4 with 100,000 miles.
The motor started with a sound as a faulty plug wire so I changed plugs, wires, lifters, oil pump and finished doing a complete overhaul, and the same sound was present.
The check engine was on with
P0401 EGR insufficient flow
P0325 Knock sensor
So I decided to change the motor from a rollover car I had with a 5.4 (which is the same setup). This motor came complete with the computer so it was just a swap of one week and was ready to go.
Here comes what made me come to an end point, the check engine came on with the same codes. I did a scan and found the value of reference of the computer to be at 6.5 volts but this value is under 5 volts measured at each sensor.
This is where I am and don’t know where to go, I would appreciate any help.
Thanks

 

I'm confused as to what you are saying, so I'll ask a few questions and then maybe others will then chime in.
What does a faulty plug wire sound like? Or are you saying that it started misfiring?
This complete overhaul - did it include pistons/rods/bearings? Valves? Timing chains/guides/tensioners?

Do you think the insufficient EGR flow is causing a spark knock that the P0325 is picking up?

Are you using the EGR valve and knock sensor from the old motor or from the 5.4 motor? Are you using the PCM from the 4.6 or from the 5.4? And are you using the wiring harness from the 4.6 or the 5.4? What year and model car did the 5.4 motor come from? Which ever harness you are using, is the octane shorting bar in place?

Did you measure VREF at the computer's pin #91 or did you display the PID VREF?

At which sensors did you measure VREF at <5.0 volts? If you are measuring VREF at different points and getting different values I'd suspect a short within the harness.

Okay, people, jump in here and help this fella out.

 

Hi pdqford
Thanks for your interest, let me give you a briefing of what happened today it has me really amassed of what a faulty scanner can make.
I was all wired up and took the car to a friend that has a new scanner (he bought it last month) and the codes were totally different, and the one that was more important was an oxygen sensor on bank 1 position 2 So I went and changed them all, problem solved,.
Took the car for a spin of 300 km to bring a trailer and no more check engine appeared.
So I appreciate your interest And will answer some of your doubts.
Faulty plug wire for me is a sound of a spark jumping from a bad contact (sorry but this is the best interpretation from Spanish to English, and I know I am not doing so well)
Complete overhaul is everything except sleeves
In my opinion the insufficient flow on the egr was causing the knocking
I wasn’t using anything from the old motor, everything was from the 5.4
The vref was taken from the scanner and was at 6.5 With the tester at the sensors was at 5
This problem had me crazy and made me spend a lot of money due to a bad scanner, I am so angry at myself for being so confident on the computers and will never happen again. It made me spend too much
Thanks for your interest and help
Emilio