Rough Idle & Misfire No Codes - 2007 Ford F150 STX 4.2L 285k miles

cadman777 wrote: Chad,

Thanx for your detailed reply (including that excellent Tutorial link! I'm still foggy on reading the 'ramped' wave forms. Your overlay chart is superb!).

With the waveform you showed... you are reading the injector voltage waveform. To get the current ramp you'll need to use a current clamp to see the "ramped" waveform. And also, I think some Fords have all the injectors powered from a fuse in the fuse box so if you had a fuse loop and a current clamp you could read all the injector ramp waveforms in one shot without removing the intake manifold. Also, I never saw what your actual fuel trim numbers were. You were kinda guessing. Find out what the LT and ST fuel trims are at idle... then raise the RPMs while watching your fuel trims. Do they get better or worse. If LT shows -7 and ST shows 4... your total fuel trim isn't bad at -3. Also when it comes to fuel trims, you should be within +/- 10... not 20. Does it have a MAF sensor and a MAP? If so... what is the G/s PID reading at idle? Take it for a test drive while watching your O2 sensors and do some WOT runs. Does the voltage go high/rich during WOT or do they go lean/low voltage? This way we can get you pointed in the right direction as to Air or Fuel delivery or Vacuum leak or MAF problems. You said you pulled each plug wire off at the coil and it had good spark... I'm assuming it would jump at least an inch... and for every plug wire you removed... you heard a corresponding RPM drop? Well thats all the homework I have for now I guess lol

Great advice!
That'll be my next hookup.
Actually, I did get the injector current way at the beginning, but forgot to record it or lost it somehow.

There's a lot to learn, and until I get my bearings on these diagnostics, I keep forgetting to do stuff.

I did get the fuel trims, but I'm gonna do all that stuff again.
I forgot how far the spark jumped, but it was a good distance.
Gonna do all that again now that I'm getting used to doing it.

Can't figure out how to print your message.
Usually I select what I want to print and then print 'Selected only'.
Gotta print it.
No way I'm gonna remember all that!

Here's a brief update on this guy's truck:

Since all the wave forms looked pretty good to me I told the owner to run a can of BG44K through his engine. He tells me it runs WAY better after the first can. I told him to run another can through it and tell me the results. This sounds like the engine's values had that nasty coke buildup on them.

I also told him to go to the local auto parts store and get them to hook up their battery/system analyzer to his battery and test the whole system, b/c he was having problems w/the starter (new) intermittently not cranking the engine. With the key off they saw a gradual drain and gradual rise in current. It was a sign wave with a period of about 10 seconds.

That would probably explain why other things intermittently work and stop working, such as his radio. Now I need to track down that drain in power.
Should be fun!

Meanwhile, the jury's still out on the runnability problem...