BarryKH

I have found in my 60 years of shade tree mechanic work, that when I have an issue like you are describing, the very first thing I do is give the cable connectors and the battery terminals a very good cleaning. Although they look clean and you don't see any corrosion, there is a gray film that develops on them that causes that. Clean them with a wire brush, the battery and the cable ends, reconnect them good and snug, and I spray my with battery terminal protector I get from the auto parts, and it does a great job preventing this. When you can no longer see the red tint on the terminals, clean them again and respray with a light coat. I hope this helps. Many issues like yours are caused by clean looking terminals. Just my experience that I've had all these years.

I have not had this problem, but I would start by checking the axles, make sure the splines are not stripped. I would check everything I could like that before opening the differential. I seems as if the actuator motor is working, but I would be sure by having someone help me by having a hand on the actuator when you try to engage 4wd. I will try to do some research and see what I can come up with. Sorry I can't be more help.

I think I have finally fixed the quirky engine. I recently purchased an Xtool D7 Scan Tool. I did an idle relearn and reset the fuel/air ratios. Since doing this I have not had an incident that I called Quirks. Been a month to 6 weeks since I did it, refilled gas two or three times and no problem with starting after filling. I was grasping at straws, but couldn't stand to give up and let it go. It may not be fixed, but so far it seems to be.

I have cleaned the throttle body thoroughly, put a new cannister purge valve on, new fuel cap, ran full diagnostics with scan tool, no issues showing up.

2013 GMC Sierra SLE with 5.3 LC9. AFM programmed out. Sometimes when stopped at traffic light, or if left idling for a minute or two, when putting in drive it stumble and dies if you give it gas. If you let it idle in drive, it will take gas and go. Only happens at times when idling for a few minutes, then trying to take off. Besides that, runs great rest of the time. Bugs me that I can't figure it out. Anyone else had this issue?

Disconnect the battery and leave it for 30 minutes or so. Reconnect it and try to start it.

My grandson has a 2014 Ram that kept getting misfire code on a cylinder. All the fixes didn't fix it until I finally found through research that the PCM could be reset by going through a reset by using the ignition and a sequence of other things, i can't remember all of them, but I tried it and lo and behold it worked. I'm a GM man myself, but Chrysler Corp has them beat when it comes to resets and things of that nature. Of course the guy who posted this had a friend in the Dodge service dept.

You said the AFM boondoggle was deleted, which is great. I think the engine probably has an AFM delete kit which is new lifters, cam, valve springs, push rods, etc, which makes for a much, much better breathing engine. I would be very happy with it. You have 8 cylinders breathing air as they were meant to. Just my opinion since I have a 2013 GMC with the 5.3 LC9. It is programmed to not cut back to 4 cylinders, but it still isn't the air pump it's supposed to be. I reiterate that I believe you have a V8 engine doing what it's supposed to be doing.

I would look for something loose in a muffler or catalytic converter, or a loose clamp or bad seal in the exhaust system. The sound is not consistent enough, to me, to be a lifter tick. My grandson had a leak in his exhaust that sounded like a tick, but a clamp had worked loose and the gasket between the pipes was leaking. Just my thoughts from the experiences I've had. Sometimes I'm right, sometimes I'm wrong. But I have learned in my 74 years to do just what you're doing, ask others for advice from their experiences. Experience is worth more that all the books.

My grandson bought a 2006 Colorado LT1 crew cab 2wd z71 and only has one key and remote. The key is not chipped, but I was told to get the key part # by using the vin and they could help me with the keys I ordered and had cut not working. Do I have to go through a locksmith or dealer to get the part # for the key? Anyone else had a problem getting spare keys made that work? Thanks in advance.

I've noticed that going up or down hills if I let off the accelerator, the engine revs up to 1500 to 2000 rpm. I know the electronic throttle is position sensitive, but is it supposed to react to this? Is this a sign of a bad sensor, or normal? What is involved in converting it to a cable throttle, which is stable in any position of the vehicle.

I kept having fuel cap problems on my cadillac and it turned out to be the purge valve. I replaced it and haven't had any problems since. I think the purge valve could be sticking a little sometimes making it seem like a vacuum leak. I don't know, it never fails to start, just sometimes you hit the starter and it will spin over for several seconds before it starts. I have even suspected the accelerator pedal module, I'm just trying to figure it out without spending a bundle on parts I don't need. Sometimes, after idling for a minute or two, and you start to take off, it stumbles, and will die if I keep trying to give it gas, but will start right back up and run fine. If it stumbles and I just ease back off the gas and give it a few seconds it picks up and goes. It has me puzzled. I am far from a master mechanic and depend on advice from folks like you for help when I'm in over my head. Many thanks.

Does a failing Evap Purge Valve always throw a code. My 2013 Sierra sometimes cranks but won't start for a few seconds, DIC shows tighten fuel cap pretty often. I cleaned the fuel filler neck and installed a new cap, but still get the DIC message often. Sometimes if stopped for a minute or two at idle, it doesn't want to take gas and accelerate. Could the Purge Valve cause this without throwing an error code? No check engine light either.

I can't seem to find a replacement fuel filter for my GMC Sierra SLE LC9 5.3. GMparts says discontinued, but has a fuel filter kit. What gives? A Change?

2013 GMC Sierra 5.3 LC9. I have a lifter or something ticking, but no misfire or other symptoms. Could this just be a loose rocker? I seem to notice it more at first startup of the day when the engine has cooled overnight. The AFM has been disabled, I think, I bought the truck used, but it never goes out of V8 mode. Any thoughts? Any experiences like this? Thanks in advance.

I've got a 2013 GMC and have a ticker in it, but so far no misfires. If I have the kind of problems you all are having, I'll probably try to find a Hemi and make it fit. You know as in Blasphemi, on Roadkill. These AFM engines appear to be nothing but continous headaches. I didn't realize they were in the GMC's until after my purchase. I got it used. I think someone before has already programmed the AFM out, as it stays in V8 all the time. Never seen it in V4. GM boondoggle in my book.

My LC9 is acting weird. I bought it last year, and I think the AFM has been programmed out as it has never disabled any cylinders, but that's great, I didn't want it anyway. But I've noticed 3 or 4 things that are weird. Sometimes after stopping, light, sign, etc when starting to accelerate it tries to quit, let of accelerator and after a few seconds it's ok, and takes off, but I have had it to die. I turned the ignition off for a few seconds and it started right up and ran fine. Sometimes when I start it, it just winds on it's own for a few seconds and finally starts, but if you turn the ignition off, and try again most of the time it starts right up. Lastly, I noticed that when stopped and holding the brake, at a light or sign, etc. if I let off the brake and try to accelerate, the engine revs a little then the trans grabs hold and jerks. I have put it under hard acceleration and pulled heavy trailer loads with it and it has never slipped or given any problems, anyone have a clue what is going on. I never get any codes. Only thing I get is tighten fuel cap occasionally, but I put a new cap on and cleaned the neck good with WD-40, and so far, so good with that. I have cleaned the throttle body with cleaner and rags, cleaned the MAF with MAF cleaner. Is this just a new GM thing I have to put up with. I've owned GM vehicles since 1965, a 1958 chevy to start with, and never had this kind of issues. Is this part of the AFM boondoggle? Thanks for any suggestions or help with these issues. You guys and gals are great.

Use your parking brake on an incline and let the brake hold it, then place in Park. As for coming apart and not breaking, there may be some little something you're missing when you connect it back together. I've had one to break when it was parked on an incline, not one since I use the parking brake. Do a youtube search on installing a new one and see if you're making a mistake reconnecting it or routing it. That's what I do. Sorry I can't offer more.

I've been noticing on the intake tube, right in front of the throttle body, is a square box like area protruding out the front of the tube. What does it do?

You didn't let any water get in the intake ports on the heads when removing it did you? If so may have water run down into cylinder and trying to hydro-lock. Take the plugs out and try turning the engine over and see if the knock is still there. Water will not compress.

Is a dealer or locksmith the only option for programming a keyless entry remote for 2013 GMC Sierra?

I recently cleaned the throttle body and it seemed to help my problem. It seems as if the harder I drive it, the better it runs. Maybe it just likes to be hot rodded a little. I'm 72, but still like to feel that power and listen to the exhaust rumble and the roar of the throttle. I'm not as up to date on these engines as I was with the old 327, 350, and especially the 396 I had in the red on red 1966 SS396 Chevelle.

2013 GMC Sierra crew cab 4X4 with LC9 engine. I am pretty sure the previous owner had the AFM programmed out of it since it has never been in 4 cyl mode. I can't even get it to go into it. The problem I'm having is sometimes when I start it, the engine starts and sounds like it's flooding out, never smell fuel, just barely runs for 2 or 3 seconds then idles normally. Sometimes I turn the switch off and restart it, sometimes it does it again, but mostly it starts and runs fine. Other times I've been driving and stop at a light, or for other reason and it won't take off, just barely runs, but I put it in neutral or park and turn it off and restart it and it's fine. I've checked it for codes and there are none, I disconnected the TPS and cleaned the throttle body, which wasn't bad at all, compared to a lot of them I've cleaned. Reconnected the TPS and drove the truck and it seemed better but still does the same thing. This is not happening every time I drive it, maybe once a week, maybe twice, if I drive it everyday. Could the TPS cause this without throwing a code or any lights flashing or coming on. I just bought a new TPS and spark plugs, but haven't installed them yet. The truck has 156,000 miles on it. I've only had it about six months.

Thanks, I'll give it a try.