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Discussion Starter #1
Went on a short trip yesterday (100 miles round trip) at about 60 miles per hour and car started missing at idle to the point it would almost die. Checked codes and found P0101, P0300, P0171, and P0174. Changed front four plugs (out of time to change all) and cleaned MAF now only have P0174 after about 20 miles of driving. Any ideas?
 

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Deville
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Had the same problem in my 02 deville. It was the plenum. Had to get it at the dealership but was only 20 or 30 bucks. Cost me like 150 at my mechanic to fix. Worked perfect. When the plenum was torn it felt like it was misfiring and the trouble code said the left bank was running lean. Dont listen to auto zone cause they will tell you its the maf. Hope this helps u out bro!
 

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Discussion Starter #3
Thanks for the input! What and where is the plenum? I just found what a MAF was yesterday.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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If you'll do some searching here and in Seville and Northstar Performance you'll find enough on "plenum" to fill a telephone book.

The plenum is the rubber/metal connector between the throttlebody (TB) and intake manifold. It is subject to cracking in the '00 - '03 Northstar series. #2 in the intake manifold drawing points to the plenum. 3 hours with simple tools and patience.

Get a Factory Service Manual - NOT Haynes or Chilton's - and do some homework. You'll need the references to study.........
 

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Discussion Starter #5
Thanks for information about plenum. I just took the cover off to look at intake and I can hear a hissing sound coming from that area. Sounds like air leak. How can I be sure that's it before I spend 3 hrs and $$ for parts?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Grab a spray can of Brakleen or choke cleaner. Start the car and let it idle, engine cover off. Squirt a tad of whatever at the bottom of the plenum bellows area. Idle speed change ???? Leak.

While you're in there, check the PCV vacuum line from the rear cam cover front passenger corner to the intake manifold behind the P/S pump. Also the PCV clean air supply from the throttlebody to the front cam cover. (Your car does not have a "rattle" PCV valve - it uses a fixed orifice. The vacuum line from the throttlebody to the FPR (Fuel Pressure Regulator) also.
 

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2003 DeVille
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Hey my same year Deville threw this code but does not appear to be misfiring. I'm going to listen for a leak and grab a can of choke cleaner to try to confirm this, if the choke cleaner doesn't change idle what else could this be?
 
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