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Discussion Starter · #21 ·
Over this past weekend I cleaned the MAF sensor, and replaced the PCV valve (it was the original) Drove it today as usual on my local news delivery routes, and it ran perfect, very good power, smooth idle no hesitation or other issues. About 3 blocks from being home, check engine light pops on, and you guessed it, P0171 was back. Not sure if this is an issue or not, but I found one injector, whose wires were connected like this.(should i fix this?) I'm tempted to leave it be for now and just drive it since it's not having any problems
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Fix that immediately with clean wiring. Bad signal to one injector will mean it isn't fueling properly, hence the code. It may "seem" OK due to not being physically noticeable, but there's a lurking lean-out issue in there that could get bad at any time.

Not sure why someone tapped off an injector, maybe aftermarket electronics, or crappy fix of some sort. You may need to pick up a fresh connector ($4-5 on RockAuto) and run it to clean wires up near the bundle. A clean crimp with built-in heat shrink would be best, and soldering would be a 2nd option.
 

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Discussion Starter · #23 ·
Fix that immediately with clean wiring. Bad signal to one injector will mean it isn't fueling properly, hence the code. It may "seem" OK due to not being physically noticeable, but there's a lurking lean-out issue in there that could get bad at any time.

Not sure why someone tapped off an injector, maybe aftermarket electronics, or crappy fix of some sort. You may need to pick up a fresh connector ($4-5 on RockAuto) and run it to clean wires up near the bundle. A clean crimp with built-in heat shrink would be best, and soldering would be a 2nd option.
AHA!!! The problem has been found! Would make sense as to it taking a while to trip the check engine light. I saw that this weekend while working on it, and said to myself WTF??? I believe it may have had a critter under the hood that chewed the wires.(saw some packrat poop along the front of the intake) Why they used that setup I dunno. Butt splice connectors would have been a better choice, I've used those a lot. Will get that fixed ASAP. Luckily no other wires ruined. Now once I make the repair, should I do the battery cable disconnect to reset the PCM?
 

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It'll probably be happy as soon as it's running... but since you're working on electrical components, unhooking the battery during this process would take care of 2 birds.
 

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Discussion Starter · #25 ·
It'll probably be happy as soon as it's running... but since you're working on electrical components, unhooking the battery during this process would take care of 2 birds.
I did disconnect negative terminal before making the repair, took about 10 min (5 for the repair, 5 for cussing out the numbnuts who previously "fixed" it. One of the wires in the goobered up previous fix actually pulled right out of the one terminal end. A couple photos of the much better fix are below. Will take it out on my deliveries today and see how it does.
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Discussion Starter · #26 · (Edited)
Ok..... this is getting beyond frustrating. The cleaning of MAF sensor and new PCV valve did no good. P0171 code and check engine light still comes on, and as it has been doing, only after about an hour of stop and go driving. What makes all of this puzzling is :

~ Light did not start coming on till about 4 days after I began driving it
~ Car has no issues with stalling/hesitating/rough idle/power loss, runs smooth with very good response & power.
~ I've googled the P0171 causes and related symptoms, my car is not experiencing any of them.
~ Only vacuum lines I can see under the hood is the power brake hose, and it's in good shape. Could it possibly be a ground issue? I'm not sure where all the grounding points are on a 2008 Grand Prix.
I'm as stumped as ever here.......
 

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I would go thru and check wiring integrity anywhere you see questionable. Since it was a latent issue, it probably happened for the previous owner at some point, so they cleared it and crossed their fingers until you took possession (...people gonna people). Might have to do with the same thing that nibbled your one injector harness, might be an additional finding.
 

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Discussion Starter · #28 ·
I checked the other injector connectors, they were all ok. That is what is making this hard to figure out, the fact it took several days to show, and that it only comes on after an hour of stop and go during my paper deliveries.
 

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That's the unfortunate nature of latent or intermittent issues. Now, it seems that it is just coming more frequently, and hopefully you can find anything that may still be a cause. I'd like to point to the scantool again, which would let you see when & how often the fuel trims are going far up, which can aid in the hunt, to a point.
 

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Discussion Starter · #30 ·
That's the unfortunate nature of latent or intermittent issues. Now, it seems that it is just coming more frequently, and hopefully you can find anything that may still be a cause. I'd like to point to the scantool again, which would let you see when & how often the fuel trims are going far up, which can aid in the hunt, to a point.
I will look at it, but next 2 months will be tight $$ wise ( insurance renewal and tags) but have the tool noted
 
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