Quote:
Originally Posted by Ultramaroon
Fuel delivery issues are still in play but I can't draw a straight line to the counter-intuitive poor performance at idle while improving under power. That we are dealing with a returnless system invalidates only my specific case in support of Tcoat's observation.
Nothing wrong with replacing the pump assembly. It would eliminate 1-3 in one fell swoop. You still have to drain the tank to replace the pump. 300 bucks would buy lots of pressure gauges. 
Definitely check the charging system. Do the headlights dim at idle? Does the engine stumble when everything's turned on? Cabin fan, headlights, brake lights all at once?
It occurs to me that we haven't discussed relocating coil packs. If the misfire is consistently on 5 and 6, swap a couple. They don't last forever. Worn (or conventional) plugs are hell on coil packs. |
Thanks for the ideas.
Fuel pump pressure is controllable electronically, so the best guess is it lowers the target pressure at lower rpm to put less strain on the pump, then steps it up as more fuel is needed. At some point that increase results in enough pressure to keep all 6 injectors going. It may not have a feedback loop in the control of the pump, so it is not adapting to increased pressure demand.
I think I might have a fuel pressure test kit from my grandfather, probably need a bunch of modern connectors though lol. What should the pressure be? I cannot seem find specs using my apparently weak google-fu. I suppose if it's lower at idle than it is primed but no flow that is evidence that the filter is the problem?
Everything electronic I can control works fine all together, and ecu voltage is still reading 14.2ish so I think charging is fine? Engine stumbles at low rpm as described, and is remarkably consistent.
Yeah I hear you on coil packs, but the chances of two different packs on different banks going at the exact same time are pretty low. I cleared the codes and checked again, still 5 and 6. I suppose it's cheaper to try to swap coils around before getting that in-tank assembly though...