I have a 2007 Infinity QX 56 that intermittently dies while driving. When I say dies I mean engine continues running but systems are compromised. Dash either lights up with multiple warning lights are blanks out. The engine is running but you can't accelerate, the car just coasts and other systems seem sluggish. after you pull over sometimes the car will start and be fine for awhile and other times just clicking w/o starting. after consulting this forum I decided to replace the IPDM. Car seemed to drive fine for a day then the intermittent problem surfaced again. Broke down and towed to dealer. they I need a new alternator (replaced about 3 mos ago) and it will cost approx 450 part and similar labor. Seems awfully high. The alternator was replaced by son in-law about 3 mos ago, so I know it can be done much cheaper. I just don't believe it's the alternator and I don't want to spend $$$ to fix and find out it's another issue. How could it be alternator if it's intermittent. Seems it would be either good or bad, not intermittent? Pleas!!! looking for help?

sounds like the IPDM as you suggested.

other things to check:

petrol pump
petrol lines (clogged?)
camshaft position sensor
cam angle sensor

could be a faulty harness/gremlin

did you take any trouble codes at the obd port? first place to check

could be the grounding straps (there are 3 i believe) are faulty. battery cables? alternator cables ? its going to be expensive at the dealer by nature its the dealer.

What happen to mine was that the Cruise Control sensor went bad....I unplugged the cruise control module and truck started right up. Dealer want 3500 to replace. I can live without cruise control for now

Yes I was shocked after replacing IPDM that it happened again. My biggest fear is dealer replacing items and not actually fixing problem, ie alternator. I've read various items suggesting fuel issues but it just doesn't seem to act like that. Very much seems electrical. Actually the first time it happened you could smell the distinct smell of something electrical burning out. All the wiring is basically plug and play (wiring harness) outside grounding issues. How would I even begin to diagnose that?

Cruies control sensor module? Where would I find that?

Sounds to me like it could be the alternator, to see if it is working properly, connect a multimeter/voltmeter to the battery posts with the engine running, if it is charging properly you should get a reading of around 14.3 volts.