Intermittent power loss with another weird issue

[Titek]

Just stumbled upon another issue out of nowhere. While driving or just idling there is a very brief power loss in the engine, as if someone turned it off and on in a split of a second. Electrical power is uninterrupted but I can see the RPM drop instantaneously about 500rpm and then just jump back up with a "jerk". I was sitting in the parking lot idling and the same thing happened without touching anything, it also happens when I downshift and just cruise to a stop but without the "jerking". I have checked all the connectors (MAF, TPS, IACV, all plugs and injectors, Temp sensor) and nothing is loose. What I did notice thought which is weird is that when I turn the key on to ACC without starting the engine the check engine light goes off and on randomly with a weird click (like a relay), all other lights and accessories stay on.

I measured the voltage at the pump with the key in ACC mode and it's 0. While running the voltage at the pump is 7.6V

Any idea what is going on? I'm stuck between a bad fuel pump or bad fuel pump control module.

[Titek]

Why can't I post URLs?

[rgregoryb]

You need to check your ecu codes

[Titek]

*55 - Nothing there

[Titek]

Can someone tell me why I can't post any videos or links to them? I have three videos that show the issue with fuel.

[nissanfreak12]

Your fuel pump primes the system for about 1-2 seconds when you first turn it to ON and not running. When you have the car running your fuel pump should be on and at the specified voltage you posted. At wide open throttle, the voltage should be at 12-13 volts. Na's have a 2 stage pump controller (7-9 volts and 12-13 volts) and TT's have a 3 stage pump controller(7-9, 10-11, 12-13).

Your rpms changing at idle is either going to be a bad IACV, a vacuum leak, CTS, and even possibly a bad injector or 2.

Do you have any mods to the car? Stock intake or POP filter?
Have you ohm'd the injectors yet?
Do you have any hard starting issues?
Have you adjusted the TPS or tested the TPS?

[Titek]

Yes there are times when I can't get it started and I have not adjusted nor tested the TPS. I just checked all the connectors and wires. I have checked for vacuum leaks and the only thing that comes up which is very strange is air leaking out of what seems like the rear main seal. I can't confirm 100% but I can hear air escaping through the bell housing drain hole.

Here are my mods.
JWT POP Charger
AshSpec ECU
HKS Hi-Power Cat Back
Megan Racing Testpipes
Megan Racing Downpipes
ES Differential Bushings
AMZ 1 Piece DS
AUS 550cc Injectors (new style, less than a year old)
Deleted HICAS
Deleted EGR
Deleted AIV
Deleted PRVR
Plenum Water lines bypass.

[nissanfreak12]

How long have you had this issue?

Check the TPS, its pretty easy to do.

When you cant get it started, is it hot or cold, or does it do it both?

[Titek]

Ok, just solved it. Yesterday while coming back home my Z died completely and I couldn't get it started again. The same issue I was having earlier. I checked the fuel pressure and it was fine, I checked spark and nothing. No spark on any cylinder. I checked the PTU and the coil packs and all were good. I checked the codes again and finally it popped an 11. I removed the CAS connector and found severe corrosion on the CAS itself. Cleaned it off, hooked it back up and she started the first time with no issue. My fuel pressure is still all over the place but I think that's a completely different issue. While Ohm testing the pump the resistance came out to 1.0 Ohms where the FSM says it should be .5 Ohms. Corrosion is a b*!

[DCaff300ZX]

You sir are the next Z32 owner of untold thousands to get to do a complete, thorough connector cleaning of every connector you can get to, and probably (for best results) replacing many/most with new upgraded and weatherproof connectors. Be aware that the IACV is well known to not work well period after a period of time regardless of cleaning and anything else, which also means used replacement is out of the question (personal experience). I myself did all connectors in stages to ensure working order of each area after work done, and used a "fix for sure and for good" approach versus "just do what seems necessary" one since these cars are so dependant on their sensors for correct operation.
While doing this, be SURE to check your lower boost hose connections (almost certainly loose) and realize the opportunities in each area to inspect and perhaps upgrade other maintenance items such as PCV system, boost hose clamps, etc.
Oh, and your real main seal is bad (and probably real cam seals also) if there is boost air escaping from the back of the motor...all very common.
Good Luck!