I have a 2010 F-150 5.4L 3v truck and its barely running. It died on me on the freeway and ran really rough when I tried to restart it, so I towed it home. Its misfiring really bad, backfiring (through the intake I think), dies when trying to idle, and starts spark knocking badly when in gear and any throttle is applied.
I think it may have jumped timing, so I took an oscilloscope reading from both camshaft position sensors. My scope does not have isolated grounds between each channel so I cannot do a cam/crank relationship test, so I'm forced to read both camshaft sensors simultaneously and try to interpret timing from that by comparing to known good waveforms from Picoscope's Waveform Library...
If I'm reading this waveform from my truck properly, it appears the timing relation between banks is off by almost 90 degrees!
Known good waveform from library (Bank 1 in blue, Bank 2 in red):
Higher resolution photo: https://ibb.co/vJnvwJ1
Waveform from my truck (Bank 1 in blue, Bank 2 in red):
Higher resolution photo: https://ibb.co/4grjxWq
I thought this engine is an interference engine, so wouldn't timing being out that badly have caused valves to slam into the pistons and cause catastrophic damage? There is no valve ticking, no lower end knocking, no smoking out the tailpipe.
Here is a YouTube clip I took of the truck during a cold startup (relatively speaking, it was 75 degrees outside), engine idling, and throttle was never touched during this clip (it has an exhaust leak due to the passenger side manifold being cracked, but that's an old problem that's been there for at least a year so ignore that): https://youtu.be/_AKQ7HI33kQ
I don’t understand why you cannot do cam crank measurement. If crank inductive, connect signal wire to one sensor wire and the black lead to battery minus?
I don’t understand why you cannot do cam crank measurement. If crank inductive, connect signal wire to one sensor wire and the black lead to battery minus?
I can measure the crank or camshaft independently, and they are both inductive, but when I try to measure both simultaneously it shorts the crank sensor and the truck won't start at all. My understanding is that the crank sensor and cam sensors use different grounding paths or something, and if your scope does not have isolated grounds between channels then you just can't do it. You gotta have a scope with isolated channel grounds. I tried it anyway, but like I said it won't start at all until I disconnected either one of the signals (cam or crank), then it would fire up.
Thanks for the help guys. I found the issue with the truck though. I decided to remove the passenger side valve cover (as that was the side where all the Check Engine Codes where saying the problem was) to inspect the timing chain and variable valve sprocket, and I found the entire plastic upper timing chain guide in pieces inside the valve cover and down inside the timing chain cover. Pieces of the guide must have gotten between the chain and sprockets, causing the timing to jump a few teeth.
