'96 Contour P0401 EGR Issues
The car has been sitting for nearly 2 years, but we're now trying to get it back in shape and inspected, so it can be sold. It's running pretty well, idles nice and smooth, plenty of power (for such a small engine it really surprises me how much "get up and go" it has). The Check Engine light came on, and the only code was P0401, "Insufficient EGR Flow." I pulled the EGR valve, but it really wasn't all that bad, and what I could see of both tubes weren't anywhere near being clogged either.
CE light came back on. So I checked the DPFE (EGR pressure sensor) and it seemed to function properly (voltage on signal line increased to 4+ volts as vacuum on REF port increased, and dropped as vacuum released). I then tried pulling a vacuum on EGR, and with the engine idling, it hesitates and stalls. So EGR itself seems to be OK, and EGR lines seem to not be blocked (otherwise the engine wouldn't stall out).
I then hooked everything back up normally, and pulled the power connector off the EGR solenoid. With the engine idling, I put 12 volts on the solenoid, and the engine promptly hesitates and stalls. That tells me the solenoid is OK, EGR is OK (again), and the engine vacuum is getting to EGR. While running this test, I watch the voltage increase on DPFE signal line, but only up to about 2 volts tops. I wonder if that should be higher, but this is only at idle, so maybe that's normal.
I tried replacing DPFE, and ran the above test again. This time I get an all-time high voltage of about 2.2 volts...a little bit higher than the original, but not by much. I decide to leave the new DPFE in place for now, and get the codes cleared.
I cleared the codes, but the CE light came back in short order. I pulled the lines off DPFE and tried blowing compressed air through them. There was no resistance in either line, and I can hear air coming out the other line, so nither line is blocked, and the constriction built into the main EGR line is not blocked either.
I removed the new DPFE, and reinstalled the original. I'm stumped. Is there anything else I can try?
Thank you for your help!
Insufficient EGR Flow




