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Post by guy48065 on Jun 11, 2018 14:50:36 GMT -6
I thought there was but I can't find it. Search was no help--maybe "EGR" is too short to search for.
Looking for how to remove or test the valve, on a 2G 4.0.
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Post by Marc on Jun 11, 2018 18:24:56 GMT -6
From the 2001 FSM...................  |
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Post by guy48065 on Jun 13, 2018 6:44:07 GMT -6
Thanks Marc! I guess my memory is slipping.
What are the 2 square things (1 on each side) that LOOK like EGR valves, with flex pipe on the bottom & a vac tube on the top?
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Post by Marc on Jun 13, 2018 12:53:03 GMT -6
No idea.
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tigger
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Post by tigger on Jun 13, 2018 13:01:36 GMT -6
Secondary air injection system check valves.  |
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Post by guy48065 on Jun 14, 2018 9:44:04 GMT -6
Thank you.
I decided to not bother testing/cleaning the old EGR valve. This car has been pretty good to me. After 165,000 miles I think it deserves a new one.
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Post by guy48065 on Jun 15, 2018 9:50:36 GMT -6
Well that didn't fix my rough idle & occasional stutter. I might have 2 problems. Only code remaining is P0101 - MAF sensor out of range. I need to try cleaning it--it looks fine to me. If I had actual air leaks on the intake side wouldn't I also be getting O2 sensor errors from the extra air going through?
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Post by Marc on Jun 15, 2018 12:30:59 GMT -6
You'd be getting a code indicating a lean condition if there were an air leak on the intake side. Years ago, the intake manifold gasket on my 2001 4.0 went bad, and DTC PO171 turned up......lean condition.
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Post by guy48065 on Jun 20, 2018 7:49:25 GMT -6
Marc--what do you mean THE intake gasket? There's 8 of those little buggers.
I checked the codes next day and now I have 3 that have remained constant over several days:
P0101 - MAF circuit range
P0171 - Too lean - Bank 1
P0174 - Too lean - Bank 2
How likely am I to have a leak on both banks when all 8 runners have their own gasket? I REALLY don't want to tear into the whole intake removal process again but I've addressed the sensor possibilities (replaced EGR & cleaned MAF) and it's really running rough once warm --though I don't really know whether that's from thermal expansion creating a leak or the emissions crap coming online at that point.
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RCA1186
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Rob
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Post by RCA1186 on Jun 20, 2018 9:31:07 GMT -6
That's pretty strange. The 95-99 gasket is one piece.
Check out your air intake tube. Known to crumble with age.
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tigger
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Post by tigger on Jun 20, 2018 17:13:13 GMT -6
How likely am I to have a leak on both banks when all 8 runners have their own gasket? I REALLY don't want to tear into the whole intake removal process again but I've addressed the sensor possibilities (replaced EGR & cleaned MAF) and it's really running rough once warm --though I don't really know whether that's from thermal expansion creating a leak or the emissions crap coming online at that point. You may not have a vacuum leak at all. Your MAF may be seriously under-reporting the actual volume of air going into the engine. Same result; unmetered air, lean condition. And you do have the MAF code... Check the connector and wiring, of course, but since you've already cleaned it with no improvement, you might need a new MAF... Try this; Once the engine is warmed up and idling rough, disconnect the MAF. Does the idle get better? HTH/GL |
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Post by Marc on Jun 20, 2018 17:49:51 GMT -6
Marc--what do you mean THE intake gasket? There's 8 of those little buggers. I'm going by what the dealer (Chev) that did the repair told me. |
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Post by guy48065 on Jun 22, 2018 9:57:24 GMT -6
Try this; Once the engine is warmed up and idling rough, disconnect the MAF. Does the idle get better? HTH/GL Yesterday when I got home I unplugged the MAF & the rpm's increased and smoothed out. The "chuff chuff" at the exhaust was gone. I checked youtube and see that unplugging the MAF is supposed to cause a stall. Dammit--once upon a time I knew that! It sucks getting old... |
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tigger
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Post by tigger on Jun 22, 2018 16:55:48 GMT -6
Yeah, when you disconnect the MAF, it forces the PCM to calculate the air charge using other sensors (air temp, engine speed, throttle position, etc.) instead of getting a direct reading from the MAF.
As you can imagine, this is less accurate (amd yes, can even cause a stall). Point is, it shouldn't run better, lol!
Sorry you need a new MAF, but at least now you know...
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bufo
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Post by bufo on Jun 23, 2018 11:28:41 GMT -6
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Post by guy48065 on Jun 25, 2018 12:58:25 GMT -6
...Sorry you need a new MAF, but at least now you know... Apparently I don't know much because the problem remains. Looks like I have no choice but to look for an intake leak. I'll try the spray first--maybe it'll save me from having to do the disassembly twice. |
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tigger
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Post by tigger on Jun 25, 2018 15:06:32 GMT -6
So you replaced the MAF and are still having the same issue?
Are you still getting the P0101?
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Post by guy48065 on Jun 26, 2018 9:59:14 GMT -6
I'm not sure which codes may have returned after the MAF replacement but it runs exactly the same.
Last night all I had time for was to spray cleaner here & there. It idles so rough I couldn't be sure if/when I hit a "sensitive" spot but spraying the throttle body boot flange stalled the motor. Did so a 2nd time. No definite reaction to spraying the manifold base or the PCV elbow.
I ordered a new GM boot & FelPro manifold gaskets.
It's not possible to "sneak" a new boot in there without removing the manifold, right?
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bufo
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Beautiful North Carolina
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Post by bufo on Jun 28, 2018 14:00:42 GMT -6
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Post by guy48065 on Jun 28, 2018 21:14:44 GMT -6
Parts came today.
Even as tight as things are in & around the 4.0 there was still room for a rodent under the intake!
I found no cracks in my boot and the 8 gaskets looked ok--but some were definitely flatter than others. I cleaned things up, installed the new gaskets & boot and out it back together. Torqued the 10 intake bolts and 3 throttle body/boot bolts to 89 in-lbs.
Started & ran with no issues & no leaks. Runs smooth again. Yay!
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Post by guy48065 on Jun 28, 2018 21:24:13 GMT -6
I'll post a picture or 2 in the morning when I figure out how. Apparently there's no way to do it from the mobile version of the website.
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tigger
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Post by tigger on Jun 29, 2018 0:05:49 GMT -6
Hey, congrats!
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