Recently replaced the NA motor in my 1990 model 300ZX.with a motor from a 1995 NA motor I purchased. After having one head reconditioned and replacing a couple of valves. new timing belt, replaced all hoses, It turns over, but won't start and run. Backfires. Timings out right? My mechanic says it is probably the ECU and I should get the ECU from the 95 model. The original 90 motor ran and was drivable, however when compression tested exhaust valves were leaking on 4 cylinders, pressure down to 80/90 Any ideas guys?
Motor wont affect the ECU's function, if you were mixing and matching looms then maybe there's a pin difference that would cause problems but there's very few electronic changes in the Z32's engines, just connectors that changed. So long as the connectors have been replaced with good contact and without crossing any wires I doubt the engine year is relevant. Wouldn't be surprised if the timing belt/crank is out 180 degrees but that's a guess. Check the ECU for codes (google "300zx ECU diagnostics" or look it up in the tech section linked near the top of this page under the banner) then start chasing hardware faults.
Things like the crank angle sensor and throttle position sensor do vary according to model year, so there's a clue for you there. See if you can get your hands on a MY95 ECU.
Correct. While the CPU and architecture changed significantly in later years, they will still work in earlier models so changes in sensors like the CAS and TPS will still work fine with either or. The main difference is the '95 forward TT has a boost sensor just under the nose panel, which an earlier ECU and relevant program will not 'know' about. I've used a '97 model ECU in an early Z with no issues, have not tried the other way but I can't see an issue since the wiring harnesses are interchangeable apart from some connectors needing to be replaced.
It's a MAP sensor not a boost sensor in the later models. All tt zeds have a boost sensor tho. If he's got the motor in then it came with a loom right? Put your cas center on its bolts and unplug your maf sensor. Also check the tPs is working fine. There's also a high chance the injector and coil pack plugs are mixed around. I think the vtc or O2 sensors can plug into the coil packs..
Thanks Instmatic. I'm trying to get the ECU off the 95 model, the motors out of. Yes loom came with motor.
Have recently replaced my 1990 ZX NA motor with a 1995 motor. All should be good but it won't start and a lab.scope test show erratic injector feed. Need a replacement CPU? Are you able to post a picture of the "erratic injector feed" as viewed on the scope? The waveform could be very interesting.
CAS controls the injectors, you csn take the cas off turn it by hand and hear each injector click. My bet is still wired up the injectors ass about. If your tech is jumping straight to the oscilloscope I'd be worried... K.I.S.S.
"My bet is still wired up the injectors ass about." Interesting diagnosis. "If your tech is jumping straight to the oscilloscope I'd be worried..." Why would you be worried?
I'd be worried cause it's going to be far more simple than eratic injector actuation. The injectors that fail on the ecu board are 5 and 6 because of how close that circuitry sits to the main feed. The car will still start and run. If the tech has exhausted all other measures and starts pulling out the scope and blaming actuation/duty cycle it's a good bet he is lost. Next step is to get the customer to ask an online forum right?? If it was me after seeing that I would remove the cas, inspect both sides of the guide pin, turn by hand and rule that out. Still have money on improper injector or coil routing.
