Low-RPM stumble

[Frank R]

My '09 seems to be developing a low-RPM miss/stumble. Comes on during times of light load and little, if any, throttle. It doesn't do this all the time - seems to be more prevalent after it has run for awhile and I notice it mostly when I'm backing into or out of a parking space. When it is occurring, the vehicle shakes quite a bit, and the engine sounds like a diesel Also, it seems to get better after I shift into neutral and raise the RPMs a bit and let it go back to idle. It seems to be running great under other conditions and is towing my 7000+lb travel trailer like a champ.

2 things possibly worth mentioning for diagnostic purposes:
- Towing my trailer home 2 weeks ago, it threw a P0150 code (Oxygen sensor - Bank 2, Sensor 1) which appeared while towing at 65ish MPH up a steep hill. I cleared the code, and it has not re-appeared, even while towing under similar conditions. I noticed no change in performance while the code was active.
- This past weekend, after it was sitting for about 2 hours, I started the vehicle and it stalled immediately. I started it again and again it stalled immediately. The 3rd time it started, stayed running, and has ran fine since - besides the low-RPM stumble of course. It has thrown no other codes.

Just wondering if anyone here could point me in the direction of things to investigate. Any assistance will be greatly appreciated.

 

[WhiteFalcon]

It is a 3 valve? That sounds very similar to what happened when my timing chain tensioners failed. The stumble got worse over time until I changed the chains, guides, phasers and tensioners.

 

[Frank R]

Yes, 3 valve 5.4l.

Not the news I was hoping for, but thanks for the input. Any other symptoms that you noticed?

I didn't mention it in the original post, but it has just under 90,000 miles on it right now.

 

[JExpedition07]

Likely VCT solenoids that feed oil to the phasers, common symptoms of failure are rough operation/ stalling at lower RPM. I’d google it and check it out. Easy part to change but valve covers need to come off.

 

[WhiteFalcon]

The VCT is a good idea. Forgot about that. My tensioner went out at 215000 miles. So at 99000, you are hopefully far from that. I drove with the stumble for about 5000 miles before I bit the bullet and changed the timing set. It was a pain, but worth it in the end.

 

[WhiteFalcon]

I also got the timing chain rattle at startup. That is when I decided that it was time to get the chain set replaced. Sure enough, the right side guide was broken and letting the chain slap around.

 

[jeff kushner]

I owned two 5.4's and both developed a small leak on the passenger side of the engine, near the firewall on the vac tube(approx 1/2-5/8" OD)that makes a very sharp shaped bend. It lays on the valve cover and slides B&F over time developed wear leaks..both trucks...slide your fingers underneath at idle and see if you feel the leak and the idle cleans up.....a good place to start too....

jeff

 

[Matticus]

I'm having this issue on a rebuilt motor (rings, main bearings, timing components, etc) that was just put in my 2012 a month ago. If I'm only giving light throttle, the engine goes through gears 1-3 a bit erratically....like it's either getting sporadic amounts of fuel/miss firing and/or the transmission is confused as to which gear it's supposed to be in (which I assume could be caused by the aforementioned) . The tach will sort of waver by a few hundred RPM's. My gas mileage has dropped about 15%-20% also, but I figured that may just be because the engine is still tight and needs to be broken in. Otherwise, the engine seems to run great and has the power I would expect. I'll upload a video of my tach under light throttle and see if you are experiencing the same thing.

 

[rjdelp7]

Starving the the phaser with low oil or wrong viscosity, may cause performance issues. It works off oil pressure. I would try cleaning your throttle body. They get caked up with carbon. Manually open it and spray cleaner. Mine was hard to clean, I had to use a small bristle brush.

 

[Matticus]

Starving the the phaser with low oil or wrong viscosity, may cause performance issues. It works off oil pressure. I would try cleaning your throttle body. They get caked up with carbon. Manually open it and spray cleaner. Mine was hard to clean, I had to use a small bristle brush.

Wouldn't this only manifest itself at higher loads/rpm? I mean the phaser part