I have a 97 f150. Have continual check engine light. Code indicated egr valve. changed egr valve, sensor, and relay. There is a constant pulse of vac. on the vac. line coming out of the relay at idle. There is strong vac on the inlet side. Also at times when I turn the ignition off the heater/ac fan continues to run and I must turn the fan switch off. The truck fast idles for way too long when I start up from a stop.(delayed shift up from first gear). I suspect computer problems but don't have a way of verifing. Any help will be appreciated.

 

What is the code? at idle youll have 1 inhg on the egr valve, when you slow rev the engine it will pulse to 3 to 3.5 inhg this should be max for the pulse or you will get a hesitation, indicating a weak egr valve spring, until the pcm corrects it, when driving it will open to 5 to 7 for egr activation

 

The code did not indicate the EGR valve but only the system has a test fault.
You shot money before you understood the issue.
Not trying to be smart but to help you get a better perspective on your problem.
What was the fault code?
The relay you refer to is the EVR solenoid.
The sensor is the DPFE.
Depends on the code as to what the test fault might point too.

 

It is my understanding the computer tells the egr valve to operate via the evr solinoid and is sensed by the dpfe. My question is what tells the computer to operate the valve? The egr valve is not supposd to open until the rpms are somewhat higher than idle speed. Right? Is the evr solinoid supposed pulse on the outlet side at all times?
The sensor lines are not plugged.
Can a computer give false signals? I have some odd things happening, I.E. The a/c fan continuing to run with ignition turned off. Doesn't the computer also turn this system on/off.
I don't have the specific code but it has been read by three different places so I think it is right.

 

EGR operation:
Remember the PCM is a computer. The computer runs on a software program.
The program software tells the hardware when and how to operate.
There are two major EGR operations.
1. The dynamic operation during driving under a specific set of conditions.
A. In OD or 3rd gears at road speeds in the 45 to 60+ mph and 'light' throttle or at lower speeds in 3rd.
2. The diagnostic routine the program goes through for each drive cycle.
A. Test for low flow rate.
B. Test for high flow rates.
C. Various other tests to detect DPFE hose faults, electrical faults etc.
.
At idle and anytime the dynamic operation is not called for there should be little to no vacuum at the EVR outlet to the EGR.
During dynamic operation your not under the hood to see it.
If you were to put a hose TEE in that line to the EGR attached to a vacuum gauge you can tell what and when vacuum appears.
Under some instances it may be of help in verifying an abnormal condition while your driving.
.
Your fan fault I assume at this time, is not related unless some other info you give links it up.
Fan/AC is not related to the EGR in any way.
Good luck.

 

I really appreciate the time you are putting into trying to help me. The main problem I am up against is I have no confidence in the people available to do the things you point out need to be checked, Ford service department included. They are not problem solvers they are parts changers according to the codes that show up on their machine. If the part changed does not solve the problem they don't know what to do other than change another part and add it to the bill.
But I guess I will return to Ford and try one more time. Thanks.

 

I'm sorry to hear that.
The dealer shop must not hire or school their techs or let them do in depth diagnostics.
Call another dealer service dept. and have a talk with them about how willing they are to solve your issues rather than guess at your expense.
Good luck.

 

I know how you feel bro, EGR problems are a very frustrating thing to diagnose. It could be anything from carbon buildup, or a vacuum line, to a bad diaphram or servo motor in the EGR valve itself. Always start with the simple stuff first and eliminate all possibilities.

 

To add to my last post an advanced part of the program that normally never gets mention.
There is a control program that has control over all routine program actions.
It is called the EXECUITIVE CONTROL.
It manages all testing, sequencing and execuition.
Without this control, none of the program routines would know when or why to run or funtion.
Good luck.