My friend and I bought an 83 NA 5 speed t-top. It had not ran in 5 years, but was complete. The man we bought it from claimed it wouldn't start due to it needing a wiring harness.

Bought it, turned out it needed an ECU. We did all the maintenance stuff, hoses, belts, fluid flushes, drained the tank etc. Everything if the fuel system that was mechanical was replaced. From the pump to the injector o-rings, everything.

In addition, using the EFI bible we tested all the sensors at the ECU and replaced the TPS, and CHTS. The VVC was physically broken so we replaced that as well.

We have also followed the guide for the intake/vacuum cleanup, without replacing the throttle body with a 60mm or the Pallnet fuel rail.

The problem we are having now is, it won't idle. It will run just find at idle RPMs but unless you press on the gas, it will die. Even my friend was able to hold the gas making it idle at 500 RPMs and it will only die if you let off completely. I'm under the impression that it has to do with the intake cleanup. Is there some significant difference in the 60mm throttle body that would make this issue non-existent?
Also, it hesitates on acceleration(not in gear), sometimes backfires, and it runs slightly rich while running.

Any help or advice would be great. Thanks!

I've done some searching and I've seen many suggestions saying the AFM could be bad. However, I've tested the AFM with a multimeter and it seems to be within specs. Unless there is something I'm missing.

 

The AFM is always a weak spot. But for idle you say you followed the clean up intake guide, So I assume the Idle Air control is now gone. On the 240SX 60mm T/B there is a small set screw that holds the throttle plate open slightly, This is the idle control for THIS set up. Look for a small screw on the factory unit. I have not seen one in a few years, so i can not recall if there is one. but this is what will control the idle now. Follow the Haynes book if you have one for testing the AFM, sometimes elect contact cleaner goes along ways for these old plugs that don't seal out moisture any more.

 

Yeah there is a little set screw on the underside of the TB on the bottom left I believe, it stops the throttle arm at idle speed, but if you cant idle you should first check your vacuum pressure in the manifold as idle problems are a symptom of vacuum/exhaust leaks. Your symptoms exactly duplicate my #6 exhaust port leak at the header, also having done the intake cleanup scenario.

 

Coolness, thanks guys. I'll check those things out and see what it gets me.

Anymore advice?