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2002 Mercury Mountaineer code problem
Hi All. I have a 2002 Mercury Mountaineer with the 4.6. Last week a message on the instrument panel came on and stayed on -"Service Engine Soon". I hooked up the OBDII and got a code of P0402 which translates to "EGR FLOW EXCESSIVE". I have searched the 2002 Mountaineer Repair Manuals and can't find any diagnotic process that tells me how to find the faulty component/item that would generate this code. I really hate to just start replacing parts. So,I would really appreciate any info that you folks can provide on this DTC of P0402. Look forward to hearing from you.
Find the EGR and bang on it with the handel of a screwdriver. Maybe, it's just stuck open a little. (By the way, this trick probley won't work. Worth a try though.) If it's not hard to remove you might try to take it off and clean it.
More than anything, I bet the DPFE sensor (or EGR position sensor) went bad. If the EGR had excessive flow, the engine would miss or run poorly.

1 Quick check you can do is this. Find the EGR valve. Its usually behind the intake manifold. remove the vacuum line to it and install a piece of 5/32 vacuum hose. Make sure its long enough for you suck on it (hehehe). Than start the engine and let it idle. Suck on the hose with all your sucking power :chin: . If the engine begins to miss and run poorly, release the vaccum slowly. If the engine runs great, That DPFE sensor is bad. The sensor is usually right next to the EGR valve. In 02, I think its square looking with a 3 terminal connector and 1 vacuum line on it.
ASE Master Tech with 15 years experience

Daily Driver: 1994 GMC Sonoma, Extended Cab, 2WD, with the 4.3 V6 Vortec.
Future plans/projects: Finishing that darn 64 Malibu SS

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