RB25DET Starts and Dies Immediately

I just had my RB25 partially rebuilt. Nothing too crazy, top mount turbo manifold, a slightly larger turbo, 550cc injectors, and a front facing intake manifold that came with a 90mm throttle body and fuel rail. It was tuned on a Haltech Elite 2000 but was password protected from the company who tuned it previously and is now closed. I reset the ECU and put a base tune from Haltech on it, and made necessary adjustments, just so we could start it and make sure there are no leaks or problems.

When we tried to get it running it would start and immediately die. We calibrated the TPS but that seemed to make it die even quicker. We played with the throttle body adjustment and recalibrated the TPS but it would start and rev at a higher or lower RPM, depending on the adjustment, and immediately die again. At one point we started it and held the throttle open around 2500-3000 rpm and it ran smooth and sounded great but as soon as we let off it died.

Any ideas on how to fix this? I’m fairly new to tuning so I still have a lot to learn but I had very experienced tuner helping me between jobs and he was having a hard time figuring it out as well. Any ideas would be greatly appreciated, thank you!

Are you still running an IACV (idle air control valve)? If not, you'll need to crack the throttle open a bit to allow air to come in the engine. (EDIT : Didn't see you already did that!)

If you want, you can post tune file and log so we can take a look and help you!

I’m pretty sure it has the oem IACV, but I’ll check with my engine builder to be sure. I don’t know how much good looking at my tune file will do, it’s just a base RB25 Haltech map with adjusted injector sizes 😅 but I’m happy to give it a try! I’ll give it another go tomorrow, log it this time, and post it.

Thank you for being willing to help!

I turns out my builder removed the IACV when he installed the new intake and I didn't even think to ask, so that's my bad. I tried to attach my tune file but it said it's not a valid file to share, sorry, like I said, I'm still pretty new to all this.

I haven't tuned an engine without an IACV before, any tips? Thanks again!

So I opened your log with Megalog viewer, but most of the data seems to be off. Like your MAP is at -100 KPA (if you are using speed density, that won't help to run your engine!), coolant temp at -6C but air temp at 20C (those 2 should be close when engine is cold). Wideband O2 is at -2147483.750 which I have no idea what it means!

Your RPM and battery voltage is working, so it did log something. I don't know if it's because it's a generic CSV instead of a Haltech Log that causes all the data to be off like that.

Tuning the idle without an IACV consist of cracking open the throttle and using ignition retard or advance to help control the idle speed. It's definitely not as precise, and I don't recommend it for a street car, but it's doable.

Wow, I guess I need to do a better job checking all my sensors. This whole thing was just supposed to be me stopping by really quick to start the car and make sure there are no leaks, so I didn’t really pay much attention to pre inspecting everything. Another learning experience for me.

When I go back I’ll actually go through all my sensors and do things properly. Thanks for taking a look at my mess of a log 😅