P0171 code after car wash

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OR VietVet

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Sunday, took the rig thru the spray car wash I have always used. When you pull in it sprays the undercarriage. Was running perfectly before this. On the way home it was only idling rough in gear at a light or stop sign. Little less in neutral or park. Rig scheduled to go in to shop the next day, Monday, for work I don't want to do, like trans cooling lines and fluid changes. I have no way of dumping the fluids. I attached my scanner and pulled a code P0171. I did not clear the cod. I did not hear a vacuum leak but also did not pull out my mechanic's stethoscope to listen. I know other things can contribute to the code setting but I had no extra time to dig in.

Anyway, while on the way to the shop it was still showing a rough idle and now the CEL was on as well. The light was not on before. The shop is gonna access the code(s) and diagnose for me while there. This is the shop where two guys that worked for me now own there own shop. Both ASE Master Techs and know what they are doing.

Three weeks from now I have appointment for the body work/paint work on the scratches at the corners of the front bumper. Thankfully, like now, I have the use of a loaner vehicle from my friend at the American Legion.
 

79jasper

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I would bet 95% of the time, those exact symptoms after the car wash turns out to be the intake gaskets.

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OR VietVet

OR VietVet

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Ok, I'll bite. Why would you guess that? Intake is on top. The spray was from underneath and no water gets past the hood.
 

79jasper

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The water will still make it's way to the top of the engine.
Exactly how I caught mine. YouTube and on the net you will find others that had the same circumstances for finding it.
I likely had a lean code before it got bad enough to cause a "misfire," but I already had a o2 code, so I wasn't checking it often.
One way I seen of testing, take a water bottle and poke a hole in the top, squirt it around the gaskets.

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OR VietVet

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Just talked to techs at the shop I use. They had not had a chance to diagnose the code yet but did check the fuel trims and found only Bank 1 side was effected and while they had the rig in the air they checked all oxygen sensor connections and found a loose connection at the front sensor and rear sensor may have been a little loose and they tightened them and they plugged them back in tight, after crimping the connector ends tighter and then checked fuel trims again and all was in spec range. Hopefully that is all it was. I will monitor after my next car wash.

Thanks for the heads up on the vacuum leak check. The thing is, I have a Tech 2 and have checked fuel trims two different times while I was plugged in for just checking and watching things and never saw a problem. I am convinced that the sensor connections problems is the source of the CEL.
 

79jasper

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Looks like I misread. I thought you did have a misfire as well.

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Just got a call from the shop. They finished all work last night and took on a road test and monitored the fuel trims on a longer test drive. Was fine and then at a stoplight they felt a rough idle, like I had before, and saw the upstream sensor on Bank 1 was dead/flatlined. Replacing with a new AC Delco this morning. I am ordering in the other 3 sensors at RA today to complete the set. They also found, while under the rig in the air that the right rear lower locating arm was bent and looked like at one time someone had used a floor jack on it. I am also ordering in all the rear arms, 2 uppers and 2 lowers, for replacement. I am also ordering in a GM replacement for the driver's side mirror that the glass was shaking on at highway speeds. It has it all, power fold, power tilt/adjust, heated, auto dim and puddle lights. I have a unlocked mint condition factory radio/cd player to replace the Kenwood radio that came with the rig when I bought it. I hate the damn thing. It is just a radio with no cd player.
 
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OR VietVet

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I got the new to me factory radio/cd player here yesterday and like was stated on the ebay ad, it looks pristine and has been programmed to my VIN number and is unlocked as promised. I also found out, when I picked up my rig from the shop, that my third brake light is out. When they did the inspection it was working then, so that means the assembly went bad. It has the proper grounds and power to it. That has been ordered from RA as well. So now have a new driver's side outside mirror on the way and the rear locating arms and the other 3 oxygen sensors. For now, that leaves the in dash control head for the heat and a/c to replace eventually. It works but the fan speed toggle switch is cracked at the faster fan speed part and at night the light that peeks thru that crack catches my eye sometimes. When all that is done I have a shop lined up to fix the scrapes at the front bumper corners and then hopefully I can just drive and enjoy what I hope is a pristine Z71. The only things that were a surprise so far are the rear arm that was bent and the third brake light. I suspected the brakes being thin but was unsure till inspected. The rest were just things that needed attention but were not bad enough to keep the rig from being driven.
 

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