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Old 08-21-2025, 09:48 PM   #1
bryansuriel3
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Blew motor got a jdm one now rough idleblack smoke

So my old motor I blew it I got a JDM motor I installed it. I’m using my previous tune I have the V1 sbd turbo kit. I used my engine harness from my old engine and all the sensors from my old engine. I put new spark plugs, new oil, new coolant, but I kept the intake manifold from the JDM motor since it looked newer started my car and my idles rough RPMs are over 1000 and they fluctuate it’s not steady I have black smoke or gray. It’s a lot. I can only run the car for like 45 seconds because It’s too much smoke. Boost gauge is reading a steady -10 even with rpm’s fluctuating. I brought new stock injectors didn’t fix the problem tried finding a vacuum leak couldn’t find it. There is an extra vacuum port on this jdm engine above the cam plate I was told to capped it off.
At this point idk what’s going on maybe i need to put back my old intake manifold/get a new tune maybe jdm cams dif/ or drain the fuel and put new fuel since its been sitting for over a year. What do you guys think the problem is?
https://youtube.com/shorts/VL49XsX8u...Qo1HnxkFL4nmHL
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Old 08-21-2025, 10:57 PM   #2
sly
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It looks like it's running extremely rich. It's hard to diagnose what the problem is because so much has changed all at once. You have a JDM engine with a different intake and you are boosting it and running a custom tune. That's a lot of variables and so it's difficult to diagnose with so many things competing with each other.

I would start simple and then add one layer at a time. Try to get it to run stock first and then build up from there. The old harness and old sensors may not be compatible with a JDM engine. What if you flashed back to the stock tune and then started diagnosing from there? The injectors are putting out way too much fuel and it could be that it's not seeing the air flow properly from the MAF. If you disconnect the MAF and let it run in open loop mode, does it improve?
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Old 08-23-2025, 02:59 PM   #3
NoHaveMSG
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Odd, there should be no difference between a JDM and USDM engine as far as I am aware. The vacuum port on the back of the passenger side head on the cam plate is because it was from an automatic.
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Old 08-24-2025, 08:44 PM   #4
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New injectors? All 8? It could be an injector stuck open. Also, as a long shot, is the DI computer properly grounded?
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Old 08-25-2025, 11:15 AM   #5
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Reason I said to unplug the MAF was to force it into open loop mode. In open loop, if the car idles better, then you are receiving bad sensor feedback from somewhere. If it still runs like crap then you may have a mechanical or other issue that would warrant further troubleshooting. To me, it's the simplest place to start.
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