My experience with AFM, poor idle and resolution

FasterBass

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Hi All,

09 Yukon 5.3 4wd 135k and counting. Picked this truck up 2 months ago and have since spent the time doing preventative maintenance. First just let me say this forum is a fantastic resource. Were it not for you folks, I'd be chasing my tail or paying a huge repair bill sooner or later. This all started with me noticing <20psi oil pressure at idle and ~30 under load.

As soon as I learned about AFM, I knew it had to be deleted and bought a second-hand Black Bear tuning Autocal unit for $50. With the tune, total was $450 and as a side benefit I got firmer shifts and a little more power out of it. Next tackled the pickup tube o-ring and deflector shield, while doing front suspension and a replacement axle. Not a terrible job. Before I dropped the pan ran some ATF through for ~10 min. Once back together oil pressure was much better with hot idle ~25 PSI and under cruising load ~40psi.

Next I took the truck to my local dealer (mistake) to have the tranny pan dropped and filter changed. I asked for them to check plugs because I had not yet done it myself. They recommended plugs and wires, and were going to charge me $600 because they "have to remove the intake plenum to change the spark plugs (LOL)" Here is where my problems start.

Upon pickup, I noticed a ticking noise that changed frequency with revs. Thought immediately that they screwed up my exhaust while removing the pan. Pissed. Looked underneath and there is nothing obvious wrong. Poking around in the engine bay with the engine running and couldnt hear where the ticking was coming from/no obvious cracks. At this point the truck still idles fine. Drive it for two days like this. Noticeably down on power.

Got new Iridium plugs and wires in (ACDELCO OEM spec) and put them in. I'm 5'8 and pretty nimble, so getting to #8 was not bad at all. Upon removing #1 plug, it almost fell out in my hand. THE DEALER HAD HAND TIGHTENED THE PLUG BACK IN and this was the noise. So furious. Anyway, fire the truck up and it is running fine.

As it starts to warm, notice that idle in drive is getting worse. I know that the PO had recently changed the motor mounts so ruled that out. Figured it might have something to do with the plugs and wires I had put in. I really would not have thought Iridium plugs could be the source of poor idle, but with so many forum members giving anecdotal evidence that they caused issues, I figured what the heck and spent $10 on regular copper plugs. Slapped those in and BAM, truck idles great! Really confusing why an OEM spec iridium plug would cause poor idle, but go figure.

Anyway, here is a tally of what I spent so far on preventative maintenance (related to engine plus tranny health... I also redid the suspension and brakes but that is a different story).

AFM Delete/Tune: $450
Oil Gasket, O-Ring, oil cooler gasket, deflector shield: ~$50
Plugs (x2)/wires: $110
D Side Valve cover: $55
Catch Can: $35
Stealership Tranny fluid + Filter: $500
All in: ~$1200
Peace of mind: Priceless
 

Geotrash

Dave
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Glad you got it sorted out. It staggers the imagination that the dealer suggested that removing the intake was necessary for the plugs on that engine, but I guess that's par for the course. If you're going to pay a premium price, I guess you might as well get misinformed too, so that if you're a clueless owner, you'll feel better about paying the extra money for the privilege. Clearly, you're not a clueless owner. It's a curious facet of human psychology that when something is expensive, we feel reassured somehow. When what matters is whether they actually do great work or not.

For transmission work, I've had much better luck with independent transmission shops. I found one near me that had years of positive google maps reviews, and they didn't disappoint. For other work I don't have the time or will to do myself, I have another local independent shop that does great work. They're not cheap, but I've never had a problem with anything they've done for me. Again, google maps reviews sent me their way.
 
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FasterBass

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Yeah fool me once. It was the literally first (and last) time I had ever brought a car I owned in for service to a dealership, because I've never owned anything new enough to warrant it. I'll be sticking with indy shops for stuff I don't have the time to do. The intake thing was mind boggling. I actually slipped up on the phone because I couldn't tell if the service advisor was being serious or not. She was serious.
 

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