ouch_my_L4L5
TYF Newbie
Hello everyone!
First post on the forum so here goes!
Thanks for all the great information I’ve found on this forum already and I hope that this post contributes in some small way.
This may be a long post and apologies in advance if this turns into a rant. Writing this out helps me organize my thoughts and remember what I’ve already done to this truck.
New to me 2007 GMC Yukon SLT Flex Fuel Vehicle, 5.3L vin 0. 4L60E, 4WD, 165,000 miles on the odometer.
I'm starting to regret ever purchasing this one. Prior to this Yukon my daily was a 2003 Tahoe LT that never gave me any trouble. Would still be driving today except for the frame will no longer accommodate the fuel tank due to rust!
Anyways, on with the Yukon.
Had the classic AFM/DOD lifter tap from day 1 when I purchased. OK no big deal.
Did a full on AFM/DOD Delete. Installed a new BTR No Springs Required Stage 1 Camshaft. (1st mistake). Replaced all lifters with LS7 style roller lifters, new lifter guides. Dropped the oil pan and blocked off the pressure relief valve, new gaskets and new oil pickup tube o-ring, GM valley pan block-off plate from the 6.0L, New 3 bolt cam timing gear and everything else that goes along with reassembly.
Lots of new parts have been installed including AC Delco Iridium Spark Plugs, New set of Spark Plug wires, new k&n panel filter, intake gaskets are new.
Long story short, I realized I had to tune the truck and turn off DOD/AFM. So which tuner to buy? Send out ECM? I opted to purchase the Diablo Sport inTune3 Platinum (2nd mistake) and have a custom tune done by Diablew. In order for Lew to do his thing with the custom tune, I have to put some miles on the truck. So, using a canned tuned from the Diablo Sport, turning off the DOD/AFM, and raising the idle in park and drive by 300 rpm, got the truck to run almost decent.
Except, while idling in Park at 900rpm the Check Stabilitrak comes on, the truck goes into open loop, and logs a pending p0300 random misfire code. Throw it in drive, and the idle is smooth with no loping, and not registering a p0300. If I keep it out of park its fine and I even drove it and set a couple of the monitors to ready. Honestly, the truck runs really well with a lot of throttle up between 3 and 4 thousand rpm, whoa watch out!
Then one day, while out running errands, the truck is stumbling and bumbling and sputtering and dying leaving me at the side of the road. Great. Hop out while it is barely running to check a few things, and find the #1 coil is not firing. I pulled the wire off the plug and aimed it toward a ground point. Not super scientific but I didn’t get shocked, and I didn’t see any spark arcing at all. OK no big deal right?
Nurse it over a couple of blocks to the auto parts store, purchase a new coil and swap it out. No change.
So, nursing the truck along closer to home (3rd mistake), I decided I better park it and walk the rest of the way. Go back later with some tools and test equipment and find that the whole driver side bank of cylinders is stone dead! No spark on any of them 1,3,5,7. Luckily this is a fairly common problem with the 5.3 as there are multiple videos of this on YouTube. Running a new ground wire the bank of coils gets the truck running on all cylinders again. Great! Get the truck home, go over, and repair all the grounds on the engine, and I thought I was done. G102 is the culprit for this symptom btw in case anyone needs that info. It is on the engine block behind the power steering pump bracket.
At this point I have reset the Fuel Alcohol Content, performed a CASE (crank variation) relearn, reset the fuel trims, and reset the idle learn.
Now the truck is running the best it has ever run. Still a little stumbling and loping at idle I assume because of the camshaft. Still throwing a p0300 every now and then but manageable. I wrote it off as the new camshaft. By the way, this cam is advertised as “Stock Idle Characteristics”. If this is the way this thing is supposed to idle with this camshaft, it is nowhere near “Stock Idle Characteristics”. A stage 1 cam should not be so dramatic that the engine thinks it’s misfiring.
Now I can drive it knowing it will not leave me high and dry at the side of the road.
After some nice highway cruising one morning, the check engine light pops on. Hmmm. Plug in the code reader expecting to see a p0300, but instead I see the dreaded p0420 for the bank 1 converter. Great.
Upon further investigation, and after trying to space out the B1S2 O2 sensor with no success, I stick a scope in the O2 sensor hole and aim it at the catalyst. Well wouldn’t you know, the catalyst is completely destroyed. All busted up, it must have melted from the raw fuel dump when trying to get the truck home running on only one bank of cylinders. This ones on me and I really should’ve known better. But to be fair, I did not realize at the time that 4 cylinders were dumping fuel down the exhaust. I thought it was only #1 cylinder and I had unplugged the injector while limping along.
So a new converter installed, and I’m back to having a good, strong running engine especially out on the open road when I can really open up the throttle.
The thing that bothers me the most is the way it idles. It idles great IN GEAR. It idles horribly in Park and Neutral. So much so that it consistently triggers the p0300 code.
Also, starting the truck I have to put my foot on the throttle just to get it to idle. Once it somewhat stabilizes, I can take my foot off and then comes the loping and p0300.
I did some further digging around under the hood. Did a smoke test on the intake manifold and found a small crack in the pcv elbow on the driver side valve cover. Fixed that and didn’t make a difference.
Cleaned the MAF sensor multiple times, cleaned the throttle plate. There are no vacuum leaks. Mechanically the engine is sound. Fuel trims look great, O2 voltages look good.
So wrapping this up, where I’m at with this Yukon is the horrendous idle, and the horrible starting.
Data logging the misfires reveals that it is misfiring on all cylinders at idle when it throws the P0300 code.
I find that if I unplug the MAF sensor while the engine lopes at idle, it smooths out. It defaults to running off the MAP sensor input and goes into open loop. So, I ordered a new Delphi MAF sensor to swap out. I am skeptical this will change anything, but it’s worth a shot.
I’m not sold on this Diablo Sport as the tuner that will fix all my problems. I have a feeling I will need to purchase an HP Tuners set up and really get into the settings. Or consult with Black Bear Performance.
Anyone have any experience getting these 5.3’s to run right after a “mild” cam swap?
Anything come to mind for anyone else?
I feel like I sunk a bunch of money into a lemon of a Yukon. Not to mention my ever decreasing budget to spend on this thing.
Thanks for reading!
First post on the forum so here goes!
Thanks for all the great information I’ve found on this forum already and I hope that this post contributes in some small way.
This may be a long post and apologies in advance if this turns into a rant. Writing this out helps me organize my thoughts and remember what I’ve already done to this truck.
New to me 2007 GMC Yukon SLT Flex Fuel Vehicle, 5.3L vin 0. 4L60E, 4WD, 165,000 miles on the odometer.
I'm starting to regret ever purchasing this one. Prior to this Yukon my daily was a 2003 Tahoe LT that never gave me any trouble. Would still be driving today except for the frame will no longer accommodate the fuel tank due to rust!
Anyways, on with the Yukon.
Had the classic AFM/DOD lifter tap from day 1 when I purchased. OK no big deal.
Did a full on AFM/DOD Delete. Installed a new BTR No Springs Required Stage 1 Camshaft. (1st mistake). Replaced all lifters with LS7 style roller lifters, new lifter guides. Dropped the oil pan and blocked off the pressure relief valve, new gaskets and new oil pickup tube o-ring, GM valley pan block-off plate from the 6.0L, New 3 bolt cam timing gear and everything else that goes along with reassembly.
Lots of new parts have been installed including AC Delco Iridium Spark Plugs, New set of Spark Plug wires, new k&n panel filter, intake gaskets are new.
Long story short, I realized I had to tune the truck and turn off DOD/AFM. So which tuner to buy? Send out ECM? I opted to purchase the Diablo Sport inTune3 Platinum (2nd mistake) and have a custom tune done by Diablew. In order for Lew to do his thing with the custom tune, I have to put some miles on the truck. So, using a canned tuned from the Diablo Sport, turning off the DOD/AFM, and raising the idle in park and drive by 300 rpm, got the truck to run almost decent.
Except, while idling in Park at 900rpm the Check Stabilitrak comes on, the truck goes into open loop, and logs a pending p0300 random misfire code. Throw it in drive, and the idle is smooth with no loping, and not registering a p0300. If I keep it out of park its fine and I even drove it and set a couple of the monitors to ready. Honestly, the truck runs really well with a lot of throttle up between 3 and 4 thousand rpm, whoa watch out!
Then one day, while out running errands, the truck is stumbling and bumbling and sputtering and dying leaving me at the side of the road. Great. Hop out while it is barely running to check a few things, and find the #1 coil is not firing. I pulled the wire off the plug and aimed it toward a ground point. Not super scientific but I didn’t get shocked, and I didn’t see any spark arcing at all. OK no big deal right?
Nurse it over a couple of blocks to the auto parts store, purchase a new coil and swap it out. No change.
So, nursing the truck along closer to home (3rd mistake), I decided I better park it and walk the rest of the way. Go back later with some tools and test equipment and find that the whole driver side bank of cylinders is stone dead! No spark on any of them 1,3,5,7. Luckily this is a fairly common problem with the 5.3 as there are multiple videos of this on YouTube. Running a new ground wire the bank of coils gets the truck running on all cylinders again. Great! Get the truck home, go over, and repair all the grounds on the engine, and I thought I was done. G102 is the culprit for this symptom btw in case anyone needs that info. It is on the engine block behind the power steering pump bracket.
At this point I have reset the Fuel Alcohol Content, performed a CASE (crank variation) relearn, reset the fuel trims, and reset the idle learn.
Now the truck is running the best it has ever run. Still a little stumbling and loping at idle I assume because of the camshaft. Still throwing a p0300 every now and then but manageable. I wrote it off as the new camshaft. By the way, this cam is advertised as “Stock Idle Characteristics”. If this is the way this thing is supposed to idle with this camshaft, it is nowhere near “Stock Idle Characteristics”. A stage 1 cam should not be so dramatic that the engine thinks it’s misfiring.
Now I can drive it knowing it will not leave me high and dry at the side of the road.
After some nice highway cruising one morning, the check engine light pops on. Hmmm. Plug in the code reader expecting to see a p0300, but instead I see the dreaded p0420 for the bank 1 converter. Great.
Upon further investigation, and after trying to space out the B1S2 O2 sensor with no success, I stick a scope in the O2 sensor hole and aim it at the catalyst. Well wouldn’t you know, the catalyst is completely destroyed. All busted up, it must have melted from the raw fuel dump when trying to get the truck home running on only one bank of cylinders. This ones on me and I really should’ve known better. But to be fair, I did not realize at the time that 4 cylinders were dumping fuel down the exhaust. I thought it was only #1 cylinder and I had unplugged the injector while limping along.
So a new converter installed, and I’m back to having a good, strong running engine especially out on the open road when I can really open up the throttle.
The thing that bothers me the most is the way it idles. It idles great IN GEAR. It idles horribly in Park and Neutral. So much so that it consistently triggers the p0300 code.
Also, starting the truck I have to put my foot on the throttle just to get it to idle. Once it somewhat stabilizes, I can take my foot off and then comes the loping and p0300.
I did some further digging around under the hood. Did a smoke test on the intake manifold and found a small crack in the pcv elbow on the driver side valve cover. Fixed that and didn’t make a difference.
Cleaned the MAF sensor multiple times, cleaned the throttle plate. There are no vacuum leaks. Mechanically the engine is sound. Fuel trims look great, O2 voltages look good.
So wrapping this up, where I’m at with this Yukon is the horrendous idle, and the horrible starting.
Data logging the misfires reveals that it is misfiring on all cylinders at idle when it throws the P0300 code.
I find that if I unplug the MAF sensor while the engine lopes at idle, it smooths out. It defaults to running off the MAP sensor input and goes into open loop. So, I ordered a new Delphi MAF sensor to swap out. I am skeptical this will change anything, but it’s worth a shot.
I’m not sold on this Diablo Sport as the tuner that will fix all my problems. I have a feeling I will need to purchase an HP Tuners set up and really get into the settings. Or consult with Black Bear Performance.
Anyone have any experience getting these 5.3’s to run right after a “mild” cam swap?
Anything come to mind for anyone else?
I feel like I sunk a bunch of money into a lemon of a Yukon. Not to mention my ever decreasing budget to spend on this thing.
Thanks for reading!
