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Discussion Starter · #1 ·
92 SC300 Aristo GTE
JDM ECU / MAP Based

So driving along this evening on the highway, get to the off ramp and sitting at the light I notice the idle is VERY low. like AT ZERO. Car is missing and I can see smoke out the side mirrors. Its dark so I couldn't tell what color the smoke was, but it smelled like rich smoke.

As I limped it the next 1/4 mile to my garage it got worse and worse to the point where I couldn't pull it in my garage. WOT yeiled 1100rpm and a lot of sputtering and smoke. Any load on the motor and it would stall.

I just got done swapping in the tranny and went for a quick little test drive and after pressing the clutch in 3rd I heard a pop and just figured it was the charge piping as I couldn't make any boost. These JDM turbos always had a little whine to them, I'm wondering if they finally shit the bed? Would it cause the car to stall and barely move, not hold idle, etc?

I checked the charge piping and it was all still connected as was the map sensor vac line and the IAT sensor.

It's almost like the MAP sensor was disconnected or something? Do the JDM ECUs have a limp mode if the MAP sensor failed?
 

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Sounds a lot like how the stock USDM (MAF) acts when it blows off an intercooler hose under boost. Since with JDM you are MAP, I think the most likely cause would be some issue with the MAP sensor or wiring back to the ECU causing bad AFR. Do you have a wideband? This would make it easy to troubleshoot if it is AFR related.
 

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Discussion Starter · #4 ·
OK, so I had to leave town for work for a week or so and didn't get any chance to look at the car.

Tonight I finally went over to the garage and figured at the very least I would install my cold cathode gauge back lighting (which came out awesome)...that's another thread though.

Car started right up! had a little misfire at around 1100rpm (warmup idle). I didn't get a chance to check the plugs as I figured they where pretty fouled up and that is what was causing the miss. Car drove pretty normal for a quick jaunt around the block. At least the stock twins are still working. Bad news is, back to square one in solving the problem. I HATE the uncertainty of a problem of this magnitude (undrivable car) as it can leave you stranded in the middle of nowhere and lets face it..the South Florida Lexus Crew likes to drive long distances.

I did eventually find a popped coupler, but I started the car up BEFORE reattaching it just to see and it went right to warmup idle and revved OK (unlike before where it wouldn't rev at all).

This is my first factory speed density (MAP) based car, but in every stand alone ECU i've tuned if the charge piping blew off, the car drove just fine in the n/a part of the fuel maps. Is Toyota different somehow? I mean I did have to drive the car about 15miles with a charge pipe disconnected, but I didn't think anything of it, since the MAP sensor is at the intake manifold and I would just drive the car home in vacuum the hole time.

What I'm getting at is, would the charge pipe being off for that period of time cause it to run so rich it would eventually foul out the plugs? In that short period of time?
 
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