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I have a 2001 DHS. It has just over 100k miles. I recently have been receiving DTC codes P0171 & P0174. I took apart the whole air induction system and cleaned it, including cleaning the MAP sensor with brake cleaner. The codes came back and now I have two other new codes, U1016 and P0101. The symptoms are when the engine is warm and/or the fuel level is low it will not idle. It idles from 500 to 1200 rpm up and down. Thanks, bluechevellekev

 Update: It seems to be getting worse. It does it more often now and the last time I drove it, when I put it in park the engine rev'd to 2k and climbed to 3k. I shut it off and restarted and the idle went to 2k. I called a shop a couple of buddies have used and going to bite the bullet and get it fixed.

Update: I took it the shop and found out that it has a major vacuum leak on the rear side of the plenum. The shop couldn't work on it for a week or so, so I'm going to replace the seals myself. If this works out to be the problem then I'm going to be pretty impressed with the shop because then didn't charge me for the I&R.

I have same dtc as you. Where is the plenum located and what is it? Thanks

[quote user="bluechevellekev"]

I have a 2001 DHS. It has just over 100k miles. I recently have been receiving DTC codes P0171 & P0174. I took apart the whole air induction system and cleaned it, including cleaning the MAP sensor with brake cleaner. The codes came back and now I have two other new codes, U1016 and P0101. The symptoms are when the engine is warm and/or the fuel level is low it will not idle. It idles from 500 to 1200 rpm up and down. Thanks, bluechevellekev

 Update: It seems to be getting worse. It does it more often now and the last time I drove it, when I put it in park the engine rev'd to 2k and climbed to 3k. I shut it off and restarted and the idle went to 2k. I called a shop a couple of buddies have used and going to bite the bullet and get it fixed.

Update: I took it the shop and found out that it has a major vacuum leak on the rear side of the plenum. The shop couldn't work on it for a week or so, so I'm going to replace the seals myself. If this works out to be the problem then I'm going to be pretty impressed with the shop because then didn't charge me for the I&R.

[/quote]I too am haveing the same problem.Must be pretty common,? did you ever fix your car,What did you do.Thanks Ron    

The plenum chambers are the actual intake manifold that is located directly under the cover on top of the engine. It is made of a type of plastic that can crack and leak engine vacumn and cause the MAF sensor to give a low air flow reading and the engine will surge on the cylinders where the crack is due to a bad fuel to air mixture. This condition will over heat the valves anf burn them out. A bad intake (plenum) gasket or bad vacumn hose will cause the same issues.