Welp, no change....same issue. Just randomly dies and farts out the intake while driving with no rhyme or reason to the madness, pop it in neutral, coast, shut off engine, restart it, goes fine again. I'm at a loss, same P0174 code I've been getting the last few days came back. That's it, nothing really helpful.....I think I might be done with this truck.....

 

Is there any chance this damn thing is out of time? Ever had the cam synchronizer out of the motor? Thinking through this, it's almost like you're off a tooth.

 

I would feel like if it was a timing related it would be having trouble all the time and not just completely random with it being cleared up by shutting the engine off and back on.

My Brother is insisting the instrument cluster is causing it. That also sounds outrageous to me, is this an actual possibility?

I also sprayed the vacuum lines and all around the intake manifold and the engine didn't react at all....I'm at a loss

 

I said it early in this thread and White has also mentioned it. Check the cam synco'r. Did you ever do a compression test? 6's don't have the power curve of the v8's so any misfire would be quite evident where you may only think you feel the same misfire in an 8.

 

I did also notice that if I'm sitting still and I hold the throttle right between 1500-1700rpms, the truck shakes a decent bit. If I hold it there a little while and then go WOT, I'll sometimes hear it blow back through the intake just before it starts to rev up....

I'll look into the Cam Syncro next......

any chance it could be the coil pack?

 

Have you confirmed fuel pressure during the rough running? If it's not getting enough gas when the engine is under a load (acceleration) that could cause a too lean condition and giving you the backfire thru the intake. Also would be why you're getting the lean code... idk just brainstorming.
AK and whitey are pretty smart so I'd still go with their current theory and check the cam synchro

 

Yeah, I monitored/logged all the fuel pressure/curves etc prior to an episode, during and after restart and they're all very consistent.

 

So did the LTFTs show a lean condition? Or were they "normal"?
If they were normal then yeah your intake backfire is not from a lean condition... which usually a truck that doesn't like to accelerate is from a motor sucking too much air or not getting enough gas.
Sometimes it can be from a misfire (which could be your Coil pack) and like whitey said would be much more noticeable in the V6.

Really the only other causes to intake backfires is timing... soooo again like mentioned the cam sync

Again just brainstorming and talking out loud to maybe flush the solution from someone's mind. I'm in no way an expert.

 

So after reading a lot on the cam synchro and coil pack issues. I decided to hop out and monitor power balance a bit.

Here is at idle for about 60 seconds.


then I slowly revved and held at 1600rpms where the vibration is the worst. (1 & 4 both dropped at the exact same time and it was when it went back to idle)



then a slow climb to 2000rpms and back slowly to idle




Any ideas from that data?

If you're all still thinking Cam Synchronizer, then I'll disconnect the #1 injector and run the power balance again to verify.

 

Maniak,

Sorry, no idea at all. JMO but I'm not sure if balance info is much help at this point. Check these videos out but first please explain for us why you are running 93 octane fuel in a 4.2 with IIRC 8.2:1 compression, when new.