EDIT: There's only 1 coolant temp sensor that I can see after reviewing the FSM documentation. it's located on the hard pipe the bolts to the back of the cylinder heads, closest to bank 1 (passenger side). I must've been thinking about Hondas, many of those models have two ECT sensors, usually one in the radiator and another around the engine block or cylinder heads.

Cheers
-Icer

 

So after trying everything above I replaced Catalytic converters with new HFC and did a complete clean re seal of injectors and plenum. Used a 12v battery and injector cleaner to service injectors. They were dirty but all atomized well by the end.

Still no luck. Car barely cranks up and has a rough idle that drops rpm and stutters. If I try to rev the car in neutral it will bog down by 3k rpm and won’t let you rev any further. Once the car is hot and turned off it will not crank again at all.

Any ideas here? I’m at my wits end 🤣

 

The ECM is not happy. It's either getting bad data from the cam/crank sensors, or your timing is way out of spec (like the chain jumped a tooth somewhere). The vehicle is going straight into limp mode, on VQs this is usually caused by cam/crank correlation issues due to bad or missing datastreams from the sensors failing.

At this point, I recommend bringing to a specialist who can interpret the live data using a high end scan tool and, if possible, a scope to check the waveforms on your cam and crank signals and ensure the firing orders are correct.

What have you done specifically? You said "tried all of the above" but what other work on your Z has been done?

Good Luck!
-Icer

 

My car is a 2004.5 DE base model
In total I have replaced the following parts with OEM or Hitachi:

• MAF Sensor
• MAF Female Connector
• Ignition Coils
• Spark Plugs
• Both Cam Sensors
• Crankshaft Sensor
• Drivers side O2 sensor

In addition I have cleaned and serviced all injectors,
Replaced fuel pump with a used pump in good condition,
Replaced drivers side fuel damper,
Replaced catalytic converters with Berk HFC after assuming cats were clogged,
Cleaned throttle body and tried relearn pedal dance (car won't re-start after warm up)
Also compared coolant temp sensor against IR thermometer and was within 1% error

The only mods relevant to the engine are a Z1 thermostatic oil cooler and a Cold air Intake with clean filter.

The car is very slow to crank and will hardly start while sounding anemic. Once it is on it idles ok but will drop to nearly 400rpm and then surge back passed 1000rpm.
If I try to rev the engine it has poor response and will not rev pass 4000rpm (I assume this is limp mode from ECM).

Happy to answer any other questions for clarity and I appreciate your response. I miss driving the Z