Here is what I have going on, we have a 1997 XLT Explorer with the 4.0 OHV, it is idling around 1800rpm & is flooding out terribly, but yet there are no codes. It will start right off the bat but as soon as you shut it off it will not restart unless you put the gas pedal to the floor. At first I thought it was the fuel pressure reg. but that bench tested fine, fuel pressure at test port tested good, thought it might have a plugged return line but can blow through that fine. Have checked for vacuum leaks but found none. 1 thing I did find was when I tested the MAF sensor connector, according to the Haynes manual I should have 10 volts or close to battery voltage between the B+ terminal & the ground terminal but I only had 4.99 volts. But if I went to the battery ground I would get 11.7 volts from the B+ terminal. So I figured I have a bad ground but then I was checking around on the internet & read in a couple of places that I should only have around 5 volts at the B+ terminal. Can anybody verify this for me? I would also love to hear any suggestions as to what else could be wrong. Will the MAF cause a high idle?
Thanks for any & all input.

 

Per the wiring diagram in the Ford factory service manual, the red wire at the MAF sensor should have battery voltage as provided from the PCM Power Relay. The tan/light blue wire is listed as the MAF sensor return, and the light blue/red wire is listed as the MAF sensor input. Given that naming convention, I would expect to see battery voltage between the red wire and ground, 5V between the light blue/red wire and ground, and something less than 5V between the tan/light blue and ground depending on the amount of air flowing through the sensor.

Before getting too hung up though on the MAF sensor, I'd suggest you monitor the fuel pressure after shutting the engine off. Does it drop rapidly (like a fuel injector that isn't closing) or does it drop really gradually?

If you have access to a scan tool with datastream mode you should be able to monitor the operation of the MAF to see if it is responding to throttle input.

-Rod

 

Thanks much for the reply Rod.
With your help giving me the wire colors & info here is my results: Red wire=battery voltage, light blue/red wire=1.28 volts, & the tan/blue=0.09 volts. I have NO IDEA why my test results are different from yesterday when I could only get the 4.99 volts. The last test I did on the MAF was to check for an open circuit on the sensor between the signal wire & ground & it tested fine.
The bad part with any of these test is that I have the high idle, which I do believe is the IAC. According to the Haynes manual I should be able to test the IAC for a internal short by putting 1 lead on 1 of the IAC terminals & the other lead on the body of the IAC & I should get around 10,000 ohms. When I did this test I received an open circuit result, there was no reading at all from my DVOM.
Next I tested the TP sensor again & again going off the Haynes manual when I test the TP signal I should have 1.5 volts & I was getting .98 volts at closed throttle & at open throttle I should have about 5.0 volts & I was getting 4.4 volts.
I did not have time today to check how well the fuel pressure was holding, hopefully I can get to that tomorrow. Unfortunately I do not have a scan tool that shows data stream.
With these test results can anybody tell me where I should start or what else I should be looking into? Could the high idle be effecting any or all of these test?
Thanks for any & all suggestions & help.

 

The correct value at throttle closed, TPS should indeed be .95vdc - .98vdc.

I suspect you have a leaky injector and a vacuum leak..... Philip

 

Well after a several hours of testing & retesting & testing some more not to mention alot of head scratching I decided to replace the fuel pressure regulator. It still would not restart after running for a minute or several minutes & I still had the high idle but it didn't seem to be flooding, judging by the wetness of the plugs. Next I replaced the ECT & WHOO HOO it idles like it is suppose to & it starts & restarts every time!! I don't understand why it didn't set a code but none the less it is fixed.

 

Great that you are all fixed up, thanks for reporting back..

Yes!, that is one of the first test we do with a full live data scanner...... Philip