I swear this truck is determined to take a framing nailer to my coffin!
2007 Tahoe 5.3L FFV, 300k on the clock.
TL;DR: I have what sounds like valve noise indicative of collapsed lifters, it's not related to the AFM (wrong cylinder(s)), and I'm trying to figure out the shortest path to fix it.
History: I learned the dreaded AFM lesson at 200k, when the cyl 6 lifter(s) collapsed, followed shortly by cyl 4, then 7. Evaluating cost, effort, and mileage, I opted for a new long block instead of a valvetrain rebuild. I put the original ignition coils and injectors on the new engine (I actually bought new coils as a PM, but when the budget route through Amazon, and within 3 weeks 4 of the Amazon coils had failed, so I just put the originals back in). I then disabled the AFM with one of the dongles.
At ~250k, the plastic side cap on my radiator decided to crack under pressure, instantly emptying the cooling system and ******* the temperature at full by the time I figured out what was going on and got parked. When the radiator blew, unbeknownst to me, the water pump popped too. Unable to find the pump leak, mostly because I'm dumb, I just kept topping off the coolant to keep her going. That resulted in a few overheating sessions when I forgot to keep up on it, but never above 3/4. When the screen on the oil pressure sensor clogged up around 1500 miles later, I discovered that somewhere in there, probably the one when the cap blew, it got hot enough to char the oil. Cue 4 oil changes with Gunk flushes, 3 oil pressure senders, and finally removing the oil pressure filter screen all together, because no matter what I did there was still a "fine" particulate of carbon floating through the system. That course of action prompted the purchase of an HP Tuner to officially disable the AFM for good.
Fast-forward to 290k, and the occasional bumble of a misfire I had been feeling for a while escalated to cylinders 6 and 8 pretty much dropping out completely, with 3 and 5 doing their best to follow suit. Through process of elimination, I landed on the OEM injectors finally giving out. Once again, I learned the budget Amazon the hard way, when the $100 set of injectors immediately sent the engine into a rich condition that could not be "tuned" out.
So a couple weeks ago, I yanked the intake, put in a $700 set of NAPA injectors, fully resealed the intake manifold, and restored the program from before I tried to remap the injectors. It wouldn't start when I was done. I learned another Amazon lesson at that point, when I discovered the $60 throttle body I had put on 20k back (while tracking down an air leak in search of relieving the misfire) was jamming every time the blade closed. I cleaned up the old OEM throttle body and threw some Super Lube on the gears, and it fired right up... at which point it was making the most gawd awful banging noise I've ever heard from an engine. It wasn't rhythmic to the engine speed, but rather kind of sporadic and sloppy.
It was so bad I pulled the intake back off, thinking I dropped something down one of the ports. Turns out, near as I can tell, I reversed the injector plugs for 3 and 5. After verifying clean cylinders and valves and putting it back together with the proper pigtails on the proper injectors, it was running great! Until a couple days later when I was greeted with the all-too-familiar feel of a misfire. Just cylinder 5 this time.
I disconnected and reconnected the plug and coil wires, and it smoothed back out. I figured it was either that OEM coil finally going out, or a loose connection, so when the misfire came back 2 days later, I just shrugged it off until I can buy more parts.
Then, last night, I pulled up to a stop light and heard the distinct sound of tappet noise. Clickita clickita clicita, with frequency perfectly matched to the revs. It has not gone away. Cylinder 5 is in a constant state of miss (indicating it's the major culprit), but cyl 6 is gaining ground with about 1/2 the rate of misfires to 5 as of this morning.
This reeks of lifter collapse, but on cyl 5, it ain't the AFM, which makes sense given that it's disabled.
I soooooo want to avoid pulling the heads and doing a top-end rebuild. So my questions are:
1. Can the lifters be replaced without pulling the heads?
2. Is there any way to free the lifters without replacing or pulling the heads?
3. Is there anything other than collapsed lifter(s) that could be the culprit here?
Any help is greatly appreciated, as usual.
Thank you!
2007 Tahoe 5.3L FFV, 300k on the clock.
TL;DR: I have what sounds like valve noise indicative of collapsed lifters, it's not related to the AFM (wrong cylinder(s)), and I'm trying to figure out the shortest path to fix it.
History: I learned the dreaded AFM lesson at 200k, when the cyl 6 lifter(s) collapsed, followed shortly by cyl 4, then 7. Evaluating cost, effort, and mileage, I opted for a new long block instead of a valvetrain rebuild. I put the original ignition coils and injectors on the new engine (I actually bought new coils as a PM, but when the budget route through Amazon, and within 3 weeks 4 of the Amazon coils had failed, so I just put the originals back in). I then disabled the AFM with one of the dongles.
At ~250k, the plastic side cap on my radiator decided to crack under pressure, instantly emptying the cooling system and ******* the temperature at full by the time I figured out what was going on and got parked. When the radiator blew, unbeknownst to me, the water pump popped too. Unable to find the pump leak, mostly because I'm dumb, I just kept topping off the coolant to keep her going. That resulted in a few overheating sessions when I forgot to keep up on it, but never above 3/4. When the screen on the oil pressure sensor clogged up around 1500 miles later, I discovered that somewhere in there, probably the one when the cap blew, it got hot enough to char the oil. Cue 4 oil changes with Gunk flushes, 3 oil pressure senders, and finally removing the oil pressure filter screen all together, because no matter what I did there was still a "fine" particulate of carbon floating through the system. That course of action prompted the purchase of an HP Tuner to officially disable the AFM for good.
Fast-forward to 290k, and the occasional bumble of a misfire I had been feeling for a while escalated to cylinders 6 and 8 pretty much dropping out completely, with 3 and 5 doing their best to follow suit. Through process of elimination, I landed on the OEM injectors finally giving out. Once again, I learned the budget Amazon the hard way, when the $100 set of injectors immediately sent the engine into a rich condition that could not be "tuned" out.
So a couple weeks ago, I yanked the intake, put in a $700 set of NAPA injectors, fully resealed the intake manifold, and restored the program from before I tried to remap the injectors. It wouldn't start when I was done. I learned another Amazon lesson at that point, when I discovered the $60 throttle body I had put on 20k back (while tracking down an air leak in search of relieving the misfire) was jamming every time the blade closed. I cleaned up the old OEM throttle body and threw some Super Lube on the gears, and it fired right up... at which point it was making the most gawd awful banging noise I've ever heard from an engine. It wasn't rhythmic to the engine speed, but rather kind of sporadic and sloppy.
It was so bad I pulled the intake back off, thinking I dropped something down one of the ports. Turns out, near as I can tell, I reversed the injector plugs for 3 and 5. After verifying clean cylinders and valves and putting it back together with the proper pigtails on the proper injectors, it was running great! Until a couple days later when I was greeted with the all-too-familiar feel of a misfire. Just cylinder 5 this time.
I disconnected and reconnected the plug and coil wires, and it smoothed back out. I figured it was either that OEM coil finally going out, or a loose connection, so when the misfire came back 2 days later, I just shrugged it off until I can buy more parts.
Then, last night, I pulled up to a stop light and heard the distinct sound of tappet noise. Clickita clickita clicita, with frequency perfectly matched to the revs. It has not gone away. Cylinder 5 is in a constant state of miss (indicating it's the major culprit), but cyl 6 is gaining ground with about 1/2 the rate of misfires to 5 as of this morning.
This reeks of lifter collapse, but on cyl 5, it ain't the AFM, which makes sense given that it's disabled.
I soooooo want to avoid pulling the heads and doing a top-end rebuild. So my questions are:
1. Can the lifters be replaced without pulling the heads?
2. Is there any way to free the lifters without replacing or pulling the heads?
3. Is there anything other than collapsed lifter(s) that could be the culprit here?
Any help is greatly appreciated, as usual.
Thank you!
