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Vacuum hose diagram needed

Tiny
HERI.OVIEDO
  • MEMBER
  • 2002 FORD RANGER
  • 2.3L
  • 4 CYL
  • 2WD
  • 280,000 MILES
I am going to look at all the components that connect with vacuum hoses because I have a fat vacuum leak or faulty part somewhere.
Thanks a lot.
Friday, November 22nd, 2019 AT 1:07 AM

7 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
A common area for that vintage Ford to leak is inside the truck on the HVAC system. You may not even hear the leak. A quick way to test that part of the system is to use a vacuum pump with a gauge on it, connect it to the hose from the intake manifold and draw a vacuum, shut off the valve and watch the gauge, if it holds move the controls to other places and see if the vacuum drops on those. If you find nothing there then you can check under the hood. The problem there is the Ford doesn't list a vacuum diagram in the information we have. Instead they put a sticker under the hood showing the lines because they vary depending on options. However a fast way to find a vacuum leak is to use a can of starting fluid or carburetor cleaner and on a cold engine you start it and spray the fluid around anyplace that could leak, like the intake manifold, lines and any suspected location. You will know when you get close as the engine will change from an idle as it gets the extra fuel.
Why do you think you have a vacuum leak?
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Friday, November 22nd, 2019 AT 2:01 AM
Tiny
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Thanks for the advice, I will try to do what you told me to, the reason why I think I have a vacuum leak is that I have a P0171 code that has been present for a long time now, I haven't done any tests myself but I took it to a mechanic and he found and fixed many small leaks on the most obvious areas like air hoses, it did improve but that didn't fix the problem completely, he replaced the EGR valve per my request because long time ago someone else told me that the EGR valve was due for replacement because it was causing the truck to misfire and I disregarded it at first due to the cost ( it's a pain in the neck to get to the EGR in this specific engine) but I thought this time it could make a difference, well that didn't work either, the code is still there plus now I am getting code P0400 system flow malfunction.
Long story short I am just trying to learn a little bit about these codes and maybe diagnose it myself, the truck works pretty well, and still misfires (specially in first gear) but not as bad as before and I drive it daily but I've spent a fortune already and I can't believe the mechanic can't find what the problem is.
Thanks I will look to the diagram under the hood.
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Friday, November 22nd, 2019 AT 6:46 AM
Tiny
STEVE W.
  • MECHANIC
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Okay, a P0171 is bank one system lean. It can be caused by a vacuum leak or a weak fuel pump. Both will cause it to run lean.
P0400 is EGR system flow. It could also be caused by a large leak or low fuel pressure as the system only tests the flow using the O2 sensors to watch the exhaust mix when it opens and closes the EGR. If the exhaust is already lean because of those reasons it will read that as meaning the EGR is stuck open and throw the flow malfunction code.

I would test for leaks but also test the fuel pump pressure. This is a generic way to test it.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

There is another item that could cause it to report those codes and that would be if the MAF sensor isn't reporting the correct airflow. If it was telling the PCM that there was less air flowing past it than there actually is it would cause the system to add less fuel at a given rpm that it needs and that would also show up as a lean code. The same issue as a vacuum leak, but no leak. I would check the intake ducting over close between the MAF and the intake manifold as a crack or tear in that would also do the same thing.
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Friday, November 22nd, 2019 AT 9:16 AM
Tiny
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Thanks for letting me know about the gas pressure check procedure, I will check that next ASAP and I'll get back here with my findings.
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Friday, November 22nd, 2019 AT 9:26 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
No problem, we'll be here. Oh, the pressure you want to see with the key on engine off and with the engine running is 60-65 PSI. Or 414-448 kPa.
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Friday, November 22nd, 2019 AT 9:45 AM
Tiny
BMDOUBLE
  • MECHANIC
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Most of the ones with P0400 code ended up needing a 9J460 DPFE sensor. You can verify this by monitoring the dpfe voltage pid with scan tool, should read.9 to1.0 volt. The sensors that have failed usually will read more than 4 volts or less than.5 volts. Very very common failure is the DPFE but also look for that vacuum leak!
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Friday, November 22nd, 2019 AT 8:49 PM
Tiny
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Interesting, after reading on the internet and forums, at some point I considered the Dpfe sensor as one the probable cause of the problem but I didn't know that one could verify that with the obd2, how would that sensor appear on the scanner? I don't see it where I see the trim and all the other parameters.
Thank you for advising.
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Friday, November 22nd, 2019 AT 9:16 PM

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