Rb25det ptu problem

[Jeffrey W.]

Hey everyone, I have a mystery problem that I NEED help figuring out.

So 2 weeks ago I bought my first import a 1992 r32 skyline gtst type m, with an rb25det engine swap, overall a wonderful car that has been nothing but a pain in the butt. I noticed the problem the first night I drove it (learning how to drive manual on it) I stalled out at a stop sign and she wouldn't start back up. Ended up draining the battery and killing the alternator. Once we got those replaced I started seeing the problem as if I drove the car around for <2 miles and it either stalled or got turned off she wouldn't start back up. Spark plugs were fine so I assumed there was bad gas (smelled like bad gas) and I replaced the fuel filter, cleaned the fuel lines along with dropping and cleaning the gas tank. Also did an oil change with a new filter for the hell of it. Nothing changed. She starts up in the morning after sitting all night and if I drive her for a while she won't start back up when she turns off or stalls. Brought it to a shop that specializes in older Nissan and they said it was probably the PTU over heating and that I should buy a new one and plug it in myself so I save money. I just wanted to get your guys opinion on this. As I said the car will start up and drive fine but it's when it stalls after being driven that it won't start up again. 

Thanks guys!

[GTSBoy]

What is a PTU?

[Jeffrey W.]

https://www.ebay.com/itm/ignition-Coil-Igniter-Module-PTU-Skyline-R33-GTS25-GTS-4-RB25DET-300zx-VG30DE-TT-/301166405761

But the one on my engine looks different than this one

[GTSBoy]

We call it the igniter.  It's just a box full of transistors that switches the power on-off to the coils when triggered by the ECU.

They do die.  When they do they play up when they're hot.  They seldom die so that you can't start the car when it is hot.  They usually just misfire a lot.

So, my guess?  It's not the igniter.  It might be, but unlikely.

The coils also die in the same fashion.  Probability of coils causing your problem also not real high.  Again, when hot they still start, they just misifre on load.

You might have dirty injectors, or a fuel pressure problem, or any of a bunch of other weird arse things.  The CAS might actually be sick, which might make some sense for it not working once warm/hot.  Same with the AFM.

[KiwiRS4T]

If you are an isolated Skyline owner you have a problem. The easiest way to eliminate problems is to swap out units with a mate with a known good engine and if there is anyone near you that would be simple. As you have cleaned the fuel system that's a start although if you could pressure test to see if the pump is up to scratch that would be good. I don't think dirty injectors are likely to give you the symptoms you describe, If you haven't already done so  installing some new plugs would be a good idea and a look at the old ones may give you some clues. While you are at it you could thoroughly clean the coils but if they are the originals they could probably do with replacement. If  you carefully mark the CAS you could take that off and turn it by hand feeling for roughness.

My guess (and that's all it is) would be the fuel pump.

[Jeffrey W.]

Tested fuel pump when I took the tank off all was good. Already took the CAS off yesterday, no roughness felt fine, got a buddy of mine to double check and he agreed. The spark plugs where recently replaced by the previous owner. Idk about coils though.