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2007 C4S with Tip and 58,000 miles

My CEL came on yesterday, due to codes 2187/2189. After a brief search on the internet,  loose oil/gas caps came up as possible causes. So I cleared the codes and tightened the caps, but the CEL came back a few  hours later.  

I also just noticed last night that, when idling in Park, it revs at ~1,100. In Drive with the break on and the car not moving (no pressure on the gas pedal) the idle revs drop to normal (around 700-800). Also the idle is a little rough. Any ideas what causes this? Thank you all.

 

 

 

 

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I would have thought the revs drop between D and P was normal. P = no load D = torque converter ready to go? Also when in park it will be in open loop mode whilst in D it will be in closed loop with idle controlled by ECU etc. (Leastways that's the way I understand it to be?) initial high idle possibly due to an induction leak?

Edited by jl-c
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The codes indicate the engine is running lean. It would help if you could monitor the RKAT fuel trim with durametric or the short term fuel trim with a generic obdii scanner that can read sensor values in real-time.

 

Without those, you can check for intake vacuum leak like jl-c said. The engine is always in closed loop fuel control other than the short period at the very beginning of a cold start, regardless of the gear position. The DME watches the a/f ratio like a hawk so it makes sense to trust it and diagnose along that "lean condition" direction - too much air or too little fuel.

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RKAT is stable at 6.984 for both banks. Just noticed that when in D and stopped, and want to get rolling and just feather the gas it sounds loud and rough (like a 1980's diesel) until the revs reach ~1,100, then it quiets down. 

Edited by Koenbro
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