I've been chasing an EGR insufficient flow DTC for awhile now. In the past, when I had this, I was always able to find a small leak in the emissions vacuum line and/or fittings. I can't find one this time.
So, I humbly ask other members since I only have one Bonneville, to help me with some normal readings. I have measured at the test port with a gauge, have monitored with scan tool to see what the MAP was reading, and, pulled the MAP sensor and bench tested it. The readings were about what they should be on a 2 Torr sensor. Reading about 2.25 at atmosphere, and close to the numbers for 5,10,15, 20,25 inches applied with hand vacuum pump. I have a variable bench DC supply that I metered to 5.00 volts to set the reference voltage when taking readings with the multimeter.
The PCM uses a series of readings taken by commanding the EGR full open during deceleration from normal road speeds to monitor a rise in MAP pressure. If the average pressure delta isn't enough, you get the Insufficient EGR flow DTC.
I also pulled the throttle body and stove pipe to check EGR passages. Found no restrictions whatsoever. The only thing I didn't check, and should have, was the stovepipe itself. Hairline cracks in corrugated steel tubing are often hard to see visually.
I just came back from a road test after it set the DTC again. At idle my boost gauge is sitting at -7. If my memory serves correctly, that needle should be buried at -10 under normal vacuum conditions. Scan tool shows the MAP indicating -8.5 to -10 at idle, while analog gauge on test port shows about 24 in. HG>
I'm kind of stumped. Mileage is around 139K, so I suppose I could have some slightly leaking intake valves, but the engine is running smooth.
Like I said, I've been down this path before with this car, and it'* usually always a leak in one of the small lines or fittings running from MAP, to tee under SC snout, to FPR, to BCS.
I haven't gone on to the brake booster and connecting hoses.
Wondering about having the PCM reflashed to current SW. It'* stock PCM. The whole car is stock as it'* the missus' daily commute car.
I swear, the SES light on this car has more bulb hours than any of the exterior lighting. Grrr...