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Old 12-20-2011, 03:46 PM   #1
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Default 01 SSEi I need vacuum numbers

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...
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Old 12-27-2011, 01:04 PM   #2
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Anyone?

I'll take wild guesses if you've got'em.
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Old 01-30-2012, 09:54 AM   #3
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Bumping this as the boss' wife'* car (03 SSEi) is giving me the same grief. We've gone through 3 different CEL codes, and I've fixed most. I've removed the EGR and cleaned, as well as the stovepipes (the corrugated and the hard pipe from exhaust manifold). The only thing I can think of is either the MAP sensor, or vacuum lines. I noticed that most of the vacuum lines under the hood are plastic, and not standard rubber tubing.

Anyone got any suggestions? Do the MAP sensors fail that often? I haven't gone into in-depth troubleshooting as I don't have access to a diagnostic machine (Snap-On Solus Pro) until Thursday and Friday during the week.
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Old 01-30-2012, 12:40 PM   #4
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Hopefully you'll get a better response than I got. I haven't gotten rid of my issue yet. I may try a MAP sensor just to eliminate that.
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Old 01-30-2012, 01:30 PM   #5
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Normal vacuum at idle for a V6 is 12 to 16 inches Hg.
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Old 01-30-2012, 01:45 PM   #6
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Quote:
Originally Posted by cliffp
I noticed that most of the vacuum lines under the hood are plastic, and not standard rubber.
Those lines are very prone to brittleness and cracking. Also check the rubber fittings that those lines go into. Bet you'll find some cracked ones if you move them a bit, especially if they are the original lines.
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Old 01-30-2012, 01:55 PM   #7
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Here is one of the best write ups on diagnosing vacuum issues I have seen:



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Old 01-30-2012, 05:08 PM   #8
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I noticed that the boost/vac gauge on the instrument cluster shows around 10inHg +/1 1inHg at idle, and the idle isn't rough or hunting. Thus, I didn't think to trust the gauge. I'll run a vac gauge inline at idle though and see what pops up. I've got tons of excess vacuum line laying around the garage so that'* a free diagnosis.

That'* a pretty cool handout, though. Thanks!

XDHD - I had figured that these lines are likely the culprit, but ran out of time before I could literally start yanking them one by one. I'm a huge fan of pressure testing the entire system (turbo guy) to determine where there are boost leaks which by nature also become vacuum leaks behind the throttle plate. I had thought about pressurizing the system to around 5~7psi to see if I hear anything hiss in the engine bay. If it'* something I hear, it'* definitely something allowing unmetered air into the cycle which obviously means that the MAP doesn't see the drop it'* expecting, and triggers the EGR CEL.

Clear as mud, I *'pose. Thanks. Will report back my findings after the evap canister comes in and I have a day to install it and remove/replace all the cheap plastic line with silicone line.
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