2007 GMC Sierra 5.3 engine problems

Bobbie Guidry · November 15, 2019

i have a 2007 (newer) Gmc Sierra SLT with the 5.3 AFM and has 207k miles. I have a variety of problems I'm dealing with and wanting to know what the best solution to these problems. I bought the truck used and had it for over a year now, the first problem i seen was a small oil leak started a couple months after i bought it. Thought it wasn't a real big deal. A month or so after a very bad lifter knock started, and the oil leak seemed to get worse. The lifter knock threw codes and had a very rough shake and very hard gear shifts and lots of smoke on start ups and low oil pressure sensor began to fail . After this happened i parked the truck for about two weeks, changed the oil and added an additive for the knock.

Soon it seemed to run a little better but didn't stop the random lifter knocks, rough running, and hard shifts. After a month or two it got better, then came the misfires. I then replaced all plugs and ignition wires and oil pressure sensor. The rough idles began to go away and the lifter knock fadded away also. A few months later i started to get engine power reduced codes after it would rain. Truck wouldn't start unless the codes were cleared. If it did let me turn over the truck, it sounded and felt like it was going to blow up. Then started it: still wouldn't let me use the throttle, so clear the codes again.

The codes read TPS sensor and TPS correlation . I then changed the sensor and still had the same problems, but would start and run , but still the pedal would not work. In the last month it started the misfire again on #6, pulled the plug and the tip was completely shattered and covered in oil. i Changed the plugs the were less than 9 months old, then two weeks after came #8 misfire with the spark plug looking the same as #6. i replaced the plug again and then did an oil change. Now my oil pressure sensor is failing again and throwing a performance issue code. The oil leak is now bad and having to poor about 2-3 QT's every 1-2 weeks.

Now Im asking what should i do with this engine, and I've delt with the these problems for over a year now. One day it runs fine then the next it starts with a new problem hopping it doesn't leave me on the side of the road one day.

Edited November 15, 2019 by Bobbie Guidry

CamGTP · November 15, 2019

Pull the engine and rebuild it. There is no way around some of the issues you are currently having. The massive oil leak is likely the rear cover gasket or rear main seal if the oil is all over the oil pan and transmission bell housing.

The AFM/DoD system is prone to failure. With that mileage some of the issues you are talking about can happen. Lifters get loud, oil consumption is up, smokes on start up or at random. The early 07-08 trucks are chalk full of issues like that.

New TPS/throttle bodys or pedal position sensors normally need a relearn done to sync things back up.

Mikebtte · November 15, 2019

What CAmGTP said, the trucks just have issues.

Get a LMF used out of a fleet van and turn off AFM. You will have a lot better of luck in the future or do a complete rebuild. Once they leaking oil you have to remove everything you would remove to complete a rebuild so you may as well rebuild.

In addition, you might have 207K on a stock 4L60E. That fresh rebuild will finish the trans off soon and you should be ready to rebuild or replace.

Bobbie Guidry · November 15, 2019

If I were to do an engine swap. What motors would be the best out of the 07-13 models ?

And as far as the the the problems with the TPS, could it be the ECM that is going bad. Again it only does it after a rain.

swathdiver · November 15, 2019

Welcome to the forum Bobbie. You might want to get a Tech-2 so you can properly diagnose this truck. You might be able to get by with a Bluethooth OBDII adapter and the Torque Pro app for smart phones. The Tech-2 can see everything electronic and read ALL codes and sensors and such from the Engine, Transmission, Transfer Case, Chassis and Body Control Modules. One or both of these tools and a subscription to AllDataDIY for the shop manual will allow to you properly diagnose problems and show you how to fix them.

Putting the truck on synthetic oil after having run conventional for its life has a way of dislodging gunk build up, turning it to sludge and creating all kinds of oiling problems. We see it all the time on the pages of these forums. Don't know if you did it, just an FYI.

As for engines, is yours a FlexFuel with yellow gas cap and badges? If so, you likely have an LMG or maybe the all aluminum LC9. If not, it's an LY5. These engines did not have VVT from 2007-2009 so if you want to swap with minimal effort, find one from these three years.

Where's the oil leak coming from? Does your truck have K5L and K34 with external engine oil cooler? The lines don't last forever and need changing at some point.

Bobbie Guidry · November 19, 2019

My plan is to bring my truck to a mechanic's house that works at dealerships to get inside of the computer and find out the problems.

@swathdiver my engine is the non flex fuel. But i was wondering if i could swap to the 2010-2013 flex fuel engines. As far as the oil leak it seems to be coming from the rear main seal leaking where the engine bolts to the tranny, but the whole bottom of the engine and tranny is covered in oil so hard to determine the leak.

CamGTP · November 19, 2019

A newer engine from 2010+ would fit but those engines came equipped with VVT. So to run that without a problem as a plug and play thing, you'd have to swap the VVT camshaft for a non VVT camshaft. As well as the front cover and camshaft sensor. Stealing the cover from your current engine would be easy.

swathdiver · November 20, 2019

9 hours ago, Bobbie Guidry said:

My plan is to bring my truck to a mechanic's house that works at dealerships to get inside of the computer and find out the problems.

@swathdiver my engine is the non flex fuel. But i was wondering if i could swap to the 2010-2013 flex fuel engines. As far as the oil leak it seems to be coming from the rear main seal leaking where the engine bolts to the tranny, but the whole bottom of the engine and tranny is covered in oil so hard to determine the leak.

Yep, as Cameron says it will work. Need to run some new wiring and programming if using the LY5s computer and you want to keep VVT. Also need bigger fuel pump regardless.