About a week later, when he encountered the problem, he plugged the vacuum line to the EGR valve and that seemed to take away his problem. He brought the vehicle back to us, but there still were no codes recorded. We removed the EGR valve to check for carbon deposits. There was no carbon buildup that could be causing a problem. Next we checked the EGR valve position sensor’s (EVP) resistance specs according to the Ford service manual. The EVP
sensor fell within specifications. Every once in a while when we ran the resistance test on the EVP sensor, the analog meter would have a slight hesitation in needle movement. We removed the EVP sensor and carefully cut it apart. Once apart we noticed a section of the resistive material on the ceramichad worn through. This worn section caused the fluctuation in the analog meter. It also tricked the computer into thinking that the EGR valve wasnot open enough. The computer would compensate by opening the EGR valve even more. Too much EGR valve will cause a hesitation, or astalling condition. We replaced it with a TOMCO EVP sensor and he has incurred no further problems.Intermittent problems can be hard to findespecially when there are no codes and the sensor involved has an intermittent fault. Thanks to an alert technician and his screeningof the symptoms we were able to help him solve this elusive problem
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