Hey everyone, I’m hoping someone with more experience with the Z32 (300zx) might be able to point me in the right direction. I’ve hit a wall trying to diagnose a frustrating issue after a full restoration.
Two years ago, I picked up my dream car, a 300zx twin turbo. It was definitely a project, having sat for about 10 years. Excited to get it running, I towed it to my garage and started the revival process. After removing an old aftermarket alarm system that was a mess, and refreshing the basics – new fuel, spark plugs, oil, and battery – it actually fired up surprisingly easily! It ran smoothly and even showed good boost. This was the green light to start a full restoration.
I went all-in, stripping the car down to almost a bare shell. There was rust in the usual Z32 spots: floor pans, roof, sills, and even a bit in the engine bay. I tackled all the rust repair, did a complete inside-out respray, and sealed everything underneath to protect it. The engine was out during the paintwork and carefully reinstalled once the body was finished. Putting it all back together was a labor of love, and I was thrilled with how it looked… until I started it up again.
From the moment the engine went back in, the idle has been problematic. I had already done preventative maintenance during the engine out phase – new water pump, timing belt, all accessory belts, cleaned the intake manifold, throttle bodies, and IACV (Idle Air Control Valve). Despite all this, the car now runs extremely rich and struggles to stay running at idle. I have to keep my foot slightly on the gas pedal just to keep it from stalling. There’s also a noticeable misfire around 1000 RPM.
I’ve been pulling my hair out trying to figure this out, especially since I was aiming to have it ready for summer driving. It’s been a huge investment of time and a LOT of money. Here’s what I’ve checked so far:
- Spark Plugs: Confirmed all spark plugs are firing correctly.
- Vacuum Leak Test: Smoke tested the entire system and found no vacuum leaks.
- ECU Codes: No error codes are present when flashing the ECU.
- Throttle Position Sensor (TPS): TPS seems to be functioning within the correct parameters.
- Idle Air Control Valve (IACV): Verified the IACV is working and responding.
- Power Transistor Unit (PTU): Replaced the PTU as a preventative measure.
- Mass Air Flow Sensor (MAF): Installed a brand new MAF sensor.
I’m really hoping someone in the 300zx community has encountered a similar issue or has some ideas on what else to check. Any help would be hugely appreciated! Thanks in advance for any suggestions you can offer.
