01-03-2013, 04:45 PM
Join Date: Oct 2011
Total Cats: 0
Car won't run with throttle open (even a crack)
The basics if you didn't see this in the engine performance section. 94 miata 99 motor, just rebuilt with Eagle/Weisco ID1000's. FM2. DIYPNP used from a member here who was running the exact setup (including ID1000's). Total newb to tuning. Pretty good with a wrench, but three kids and job plus other hobbies limit time in the garage. Love long walks on the beach.
Initially I couldn't even get this car to start for more than a few seconds, but with the addition of a proper AIT sensor (GM), getting it running enough to get an initial time on it (10deg), and going to PWM warmup mode for the idle, I've managed to keep the car running long enough to warmup completely. It idles.. sort of.
If I step on the accelerator at all (just a bit or all the way or anywhere inbetween) it richens up and revs for just a moment, then the WB shows it running to full lean and it dies (like two seconds). It reacts the same no matter what the coolant temperature is, so I doubt that the after start enrichment/tapers have anything to do with the big problem.
My goal here is to get it to work even just a little bit. And I'm at the 'completely new and pretty much clueless' stage of tuning. I have a little bit of sense though, so here's what I tried: 1/ Could it be reading incorrect manifold pressure? Unplug the vacuum hose, engine quits. Apparently that's working, and it should be since the ecu came off a working car. 2/ Add fuel to VE1. I selected all and increased in increments of 10. The mixture richened, and now it 'idles' at 2000 rpm and 12.0 AFR. Didn't make a difference when I tried to rev the motor. AFR goes to 18+ and it dies. You can feel it take the acceleration enrichment and right after that the pedal feels dead (motor doesn't react to it).
Thoughts: The VE table certainly will need tuning for this car, but I don't think that's the problem. Likewise with timing and IAT temperature. TPS has been calibrated. I probably need to mess with that again as I turned the screw on the throttle body, but it works. Probably not the problem. Fuel filter: Could be, but it runs and gets gas. A clogged filter might mess with things, but it would be more likely under load. Plus, the motor reacts the same if I even just crack the throttle.
IAC needs tuning, but again, I don't see this being the root of this problem. Could I be wrong there?
Fuel pressure: I'm a little unclear how this is working. It's a 94 with a 99 engine, so I'm using the 99 rail and the 94 fuel pressure thing turned upside down on the end of the rail. Should work.
This whole damn thing is complicated by a military move that is taking me to HI (from Washington state)... Sunday. It will suck to leave this car parked for years.
Anyone know anyone in Seattle that knows miatas and how to deal with MS?