What kind of fuel trims does it show? Anything pegged at +/- 20%? These trucks have a goofy way of checking for misfires and it often doesn't catch small ones. It reads the pulses from the O2 sensors and decides if there is something wrong if the timing between them is not even enough. The consequence of this is if your O2 sensors are shot then it won't be able to pickup misfires. O2 sensor codes are pretty hit or miss on if they will trigger with a bad O2 so make sure you look at the voltage and see if it makes sense. Is your throttle cable loose? I had a TPS fault code from that before. Should be taught but not being held open with no throttle input with the engine off. Did you make sure the rod that the TPS meshes into is not damaged or sloppy? Never seen a throttle body fail on those but its worth checking.

 

So, nothing pegged in the fuel trims, but LTFT B1 is blank. STFT B1 showed -16.4% @ 966 rpms.

One of the cables at the throttle body is loose - the other is tight. See pic.

Have not checked O2 sensor voltages.

 

Your truck is running very lean. Normal range is about +/-6%. Was there any other LTFT sensors working? If not then you probably have the downstream O2 unplugged or damaged. Check for vacuum leaks. Might try cleaning the MAP sensor as well. A good way to check for vacuum leaks is to get a map torch or propane torch and let it leak gas slightly. Be careful to not have it be too fast. Move the tip around your vacuum lines and intake and see if the engine gains RPM. Those cables are fine and not the source of the issue. One is your cruse control and will automatically tighten when you enable it.

 

yeah, the cruise control cable - makes sense.

i’ll check those o2’s - no other trims reported- scanner only shows those two.

 

OK, so here’s the big update. The last thing that I was diagnosing was the O2 sensors, when the engin started to make a terrible noise. I switch the engine off immediately and then I started looking more into this. I ended up taking off or at least taking a look under each of the valve covers and I discovered absolutely nothing. So I decided to try to turn the engine manually and in the process got to a point where the engine would not turn by hand. I ended up pulling all of the plugs and try to borescope the cylinders and sure enough in cylinder number one I could see the dreaded valve seat that had fallen out of the head into the cylinder. I never knew this was a known problem with these engines. I wish I had done a compression test from the get-go. So, at any rate, this is what the problem is with the engine - it’s gonna need a new cylinder head. Hopefully there’s no damage to the cylinder wall - the top of the no 1 piston is a little scraped up but nothing horrendous. Wish me luck.

 

If you plan on rebuilding the head have a machine shop put interference fit valve seats on them. Also replace your water pump and flush your radiator. You overheated your engine at some point which is why this happened. The 4.7 has valve seats that are too loose from the factory and will fall out if you overheat the engine at all. Really its the biggest flaw those engines have. Aside from maybe the valve seals which would also be good to upgrade.

 

This truck has never come close to overheating. Gauge has always read in the middle or slightly lower. I’m the original owner, ordered it from the factory in 2003. The only other person who’s ever driven it is my wife - only a handful of times. This engine doesn’t work hard. 65 on the freeway is 2000 rpm. I drive it 20 miles a day. I’ve towed with it a few times but it has the factory towing package and lsd with 3.92 gears. I’d say with 220k miles on it this not a huge shock. My plan is to replace the heads and timing chains. Complete heads with redesigned seats are $500 each.

 

Here’s a couple pix of the destruction. Luckily, the piston was not cracked and aside from the scarring it’ll survive. Better still, the cylinder wall is in perfect shape. The head is toast. These heads are heavy - aluminum or not. Getting it off was no picnic.

 

Are those chunkies taken out of the piston? If so, you wanna replace that. Those will create hot spots, and lead to spark knock....