Burps, stumbles, 400rpm or no start. Just fixed dogged out crank key - Miata Turbo Forum - Boost cars, acquire cats.

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Old 04-27-2014, 03:14 PM   #1
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Default Burps, stumbles, 400rpm or no start. Just fixed dogged out crank key

Last week I decided to fix the crank wobble I have been experiencing in my car. Jump to bold to get to the description of the issue but for troubleshooting purposes I am listing what I removed:
  • Valve cover, cam sensor, all assorted brackets and ignition coils/wires. I left spark plugs in.
  • All three front covers with brackets.
  • Disconnected fuel injector harness and the two plugs to the right of it.
  • Removed water pump pulley, crank pulley, crank boss, timing belt, crank sprocket.

I then located a used but in good condition crank sprocket and key and performed the loc-tite fix. There was play but it wasn't bad.

While I was down there I pulled the cover off VVT sprocket and removed it so I could clean the hole out and apply blue loc-tite and re-torque. It was VERY loose compare to how tight it should have been. I did the same to the exhaust side. (The VVT actuator and sprocket WAS off the cam for a moment. I didn't see any o'rings or anything fall out)

After the crank nose fix was cured I re-assembled everything taking time to get proper torque values etc.

This morning after I felt confident that everything was properly cured and sealed up, I attempted to start it.

It bucked, stumbled and popped and when it finally did catch, it idled at about 400rpm and only then with my foot all the way to the floor.

I verified timing twice, I checked (timing belt) tension twice, I THINK I made sure everything was connected.

After reassembling everything a second time I attempted to start it again. Same exact problem. One interesting thing, even with the throttle open, the idle valve in startup mode (47% PWM), and indicated MAP of 70-99kpa it sounds like I have a hum or resonance coming from my intake manifold area. I don't find any vacuum hoses disconnected anywhere.

After the last attempt to crank when it wouldn't crank anymore, I pulled the plugs. They are black and sooty. I don't recall them looking like that last time I pulled the plugs.

So, I am thinking here are my possible problems :

Timing could be somehow still borked. At this point I don't think it is the mechanical timing but anything is possible. Another cause might be that my old crank/keyway was so off (2-4 degrees maybe?) and now with the new master hub, cam sprocket and key, I might be back to a point where my engine doesn't need as much fuel or timing as before.

Second thought is fuel. Again though, no changes have been made in the tune and no under dash wiring has been disturbed since I put it down for the repair so aside from the grounds to the fuel injectors and the plugs at the front of the engine I can't think of anything that would cause such an issue.

Last is spark. Aside from fouled plugs which are partially a symptom of something else I can't think what else could be the problem.

So, I am looking for ideas on not only what could be the problem but how to test it and fix it. Sorry for the wall of text but I don't see what I could have posted that would be helpful (aside from tooth log which will come as soon as I get new plugs in the car and let the cylinders air out)

Thanks for the help in advance.
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Old 04-27-2014, 03:20 PM   #2
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Pretending for a moment as if I had a brand new Megasquirt build, help me go through my start-up?

Make sure timing is correct decoder, set timing to fixed 10
Set Idle PWM to??
Make sure fuel injectors are properly sized in software
How do I set my initial start values for idle? Would that be in my main VE table or would somewhere else be better for my start-up to make sure I don't over-fuel it to star? It's been so long...
What else?
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Old 04-27-2014, 07:30 PM   #3
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Disregard, problem solved. I had the damn trigger wheel on backwards.
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