This post maybe a little long but I’m getting frustrated. . .
Ok here goes. I have a 2001 F-150 4x4 SC 4.6 auto XLT ;
The check engine light came on about 3 weeks after I had it. I rented a code reader and it said “excessive EGR flow” (P0402). ( I also went to a mechanic)The mechanic said that it was most likely the DFPE which I have replaced and reset the computer, with out the light coming back on yet.
The engine has cut out on me once before I had changed anything, but now that I have changed the sensor the engine idles for about 30 to 60 seconds then the rpm’s start to vary between 500 and 1000, but not erratically.
The mechanic said that there was a code that indicated a vacuum leak (P0171 and P0174) along with the excessive EGR flow. I assume that’s what causing the rpm’s to vary since my check engine light is not on anymore.
What I am hoping someone can tell me is how to track down a vacuum leak to find out exactly where it’s coming from. I’m assuming the exhaust system is where it’s coming from.
Thanks, I hope someone can help.

Spec’s:
- 83,000 miles
- original fuel filter
- spark plugs just replaced
- new EGR valve

 

To check for a vacuum leak, I usually get a can of carb cleaner and spray around the intake gasket area, the intake itself, near vacuum lines, etc. Do this while the engine at idle, once it picks up the idle via carb cleaner, you have located the vacuum leak.
Most of the time it is intake plenum gaskets.

If you happen to remove the upper intake, be sure to clean up the egr ports. They get pretty bad on higher milage vehicles and cause EGR codes.

Good Luck finding your leak!!


FordMasterTech

 

the carb cleaner won't ignite when it hits a hot surface?

 

Ck your pcv hose, the rubber that attaches it to the back of the intake is real bad about deteriating.

 

I wouldn't say that it WOULDN'T, but it never has in my experiences. Just don't spray the exhause manifold and you should be safe.

Good Luck in finding your leak.


FordMasterTech