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Discussion Starter · #1 ·
Hello all,

New to the forum and already a big fan after reading through a lot of info. Here's the issue that has brought me here...

2007 Silverado 5.3L, 140k miles. Recently got the check engine light which was the result of the familiar P0121 code for throttle position sensor. As I've read, it was most likely the result of the throttle body being dirty (which it was extremely). I followed the how-to tips found here and cleaned it last week. Since then, I've got new issues. As expected after cleaning, I had some high idling, but that has mostly resolved itself. However, when it is idling normally, put it in gear and it rolls slowly forward like normal for about 10 feet then takes off. RPMs climb to 1200 or so and speed climbs enough to shift into 2nd without touching the gas. When slowly accelerating or holding speed up a small hill with the throttle slightly depressed (around 1200-1300 RPM) it hesitates or stutters. If I accelerate faster, it acts normal. When slowing to a stop, the RPMs stay around 1100 until coming to a full stop, then slowly come down to 600ish. Pull away from the stop sign and it takes off again. It has not thrown another code since cleaning.

I'm leaning towards a faulty throttle position sensor. Any thoughts?
 

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If you moved the butterfly when cleaning it, the ECM needs time to relearn a little. I had that code on my '08 5.3 and I ended up replacing the TPS sensor, cleaning the throttle body and cleaning the MAF. When I started the truck up after, it idled way high for a little bit. And when I first drove it, it acted a bit erratic with shifting and rpms etc. After a few miles of stop and go and highway speeds it settled down and was fine.
 

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Discussion Starter · #6 ·
Been driving around town, back and forth to work and some of my issues seem to be getting better. When I start up I no longer have what I would consider a high idle. It will rev above 1k and come back down quickly to 650-700 and settle closer to 550-600 as it warms up. Seems pretty normal. It also doesn't take me for a ride when I drop it in gear any longer, although with the RPM being a couple hundred high, it still moves you along at a pretty good pace and I find myself riding the brake more often because of it which I don't like.

The latest update however, is that I've now got the check engine light back with a new code, P0307, cylinder #7 misfire. That leads me to the problems I still have; stuttering/hesitation in the low RPM ranges (less than 1500 roughly) and sitting at a long red light tonight, the RPMs fluctuated pretty low (400ish) a couple of times and I thought it might die at one point.

I know my truck could use plugs and wires, but I'm not sure that this isn't related to my original issues somehow. Thanks for the help guys.
 

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Seems like your throttle body issue is working its way out via the ECM relearning. But it sounds like you have a new issue with the misfire code. How many miles on it? I would pull the spark plug #7 and look at it, see if its fouled. AFM in these engines gums up the plugs on those cylinders pretty good even before 100k recommended service of plugs and wires. I just replaced all my plugs and wires on my truck at about 115k. Use AC Delco plugs and wires. I bought all mine off Amazon pretty cheap and it's a pretty easy job except for #8 which is a tough spot to get at near the passenger firewall, but not impossible.
 

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I just reread your original post.....I thought you had an '08 like mine, but I see its an '07, but if its the newer body style like the '08s it may or may not have active fuel management. Either way I also see you have 140k...if you haven't had the wires and plugs done ever , it's definitely time and will probably correct your issues.
 

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Discussion Starter · #9 ·
Riley76, it is a new body style like yours and does have the AFM. I'm the original owner and have never changed plugs and wires (shame on me, I know). It had been on my short list to do when the throttle body issues started. I was hoping to resolve those before changing them, but it looks like that decision was made for me with this new issue.

I appreciate your input and all others.

One other thing came to mind after being told it could be a vacuum/air leak somewhere. Before all of my issues, I was leaving work one day and could hear a pretty pronounced whistle. At low speeds when the noise from the exhaust and tires were low, I could hear it increase and decrease with RPM. It hit me last night, that since this has started, I haven't heard it again and maybe the little pin hole somewhere that was whistling has gotten larger and no longer whistles, but now has caused trouble. Perhaps I am hyper sensitive to the little things now, but I thought I'd mention it in case a light bulb goes off for anyone.

Thanks again.
 

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Discussion Starter · #10 ·
Wanted to update the thread in case it helps someone in the future. Yesterday morning I dropped my daughter off at school. I drove alongside the covered sidewalk to the end where I stopped to let her out. When I hopped out to help her, there was a strong smell of vehicle burning rich. At first, I thought it had to have been a vehicle in front of me in line, however, as I pulled away, I began to consider that it was possibly my truck as I have dual exhaust which exit to each side. The left side was dumping under that awning which was holding the fumes quite nicely.

When I got home last night, I confirmed my suspicion by cupping my hand near the left side exhaust exit. The right side (coming off of the right side headers) does not have this odor. In my mind, this confirms an issue with combustion in the #7 cylinder since it is in the left side of the block. I have new plugs and wires (OE AC Delcos) ordered and hope to replace those over the weekend. I've got my fingers and toes crossed that this will resolve my residual issues.
 
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