Hi guys,
I have a 94 thunderbird with a 4.6L V8, and I have a stumble/hesitation upon heavy acceleration. It feels like a slight missfire, and it happens when i go uphill under steady acceleration, or on level ground giving it 2/4 3/4 throttle. It doesn't seem to make a big difference if its cold or hot, however when its hot, the missfire is more pronounced. No engine light is on, however, when i scanned it i got a P0402. That points out the egr system and says"excessive flow detected in the egr". So far, I have done plugs, wires, coils, cam/crank sensor, throttle positioning sensor,dpfe sensor without a result. I bypassed the EGR, and it still does it. The dealer said i would be wasting my money if i get an egr, and i'm better off getting a dpfe, because they are well known to break. $100 bucks later, it is not a result of my problem. Might it be the EGR valve itself, because I am trying to work around it because it is phisically impossible to change it without removing the intake. If I was to have a vacuum leak somewhere, wouldn't the symptoms be the same(but then it wouldn't throw me the same code)?