ddub

I was trying to put my timing back to stock and discovered that somehow I'm running a 0º split...

When I stabbed the CAS and hooked the timing light up to l1 and t1, both were aligned to the same mark. Car was fully warmed up, TPS was set correctly, idle was at 750, tried moving the timing clamp down further and various positions, etc.

I tried everything, along with many different idles from 600 to 1000 just to see if anything would change and NOTHING did. Timing still advances with throttle, but there is no split.

How is this possible on a stock ECU? Is something broken or going out? Any suggestions or things to check before I give up

The really odd thing is that my idle is smoother than it has been in a long time. I had the timing advanced before, slightly, and got a lumpy idle because of that. I got tired of it and wanted a smooth idle back, this is where it all started. I do have an extremely smooth idle, but how is this possible if I truly have a 0º split? If the split was truly nothing, wouldn't the idle be worse?

iceblue

It was my understanding that the factory evrything ran a 0 split and mazda recomended a 0 split and for the purpose of obtaining a smooth idle.

The marks I have read into were -5atdc for L and -20atdc for T. My asumption was the positioning of the plugs placed them at these degrees but still fired in a 0 split.

ddub

No, there is definitely NOT a 0º split in stock form!

And what I'm saying in my post, is that when I stab the CAS so that L1 aligns with 5º ATDC (shown via the timing light), when I check T1 it is ALSO aligned with 5º ATDC rather than 20º ATDC like it should.

iceblue

Ahhh thats not right.

ddub

Which is why I made this thread

RETed

From my experience, it's usually the TPS out of whack, but you've already confirm you checked the TPS...

Who cares - it still runs.


-Ted

HAILERS

The Relationship Chart shows that WHEN CRANKING WHEN COLD, the lead and trail are both 5* BTC. That's the only clue I can see. Computer locked up? Got me. Try after driving around for a while.

ddub

Welly welly well. I think I might've found the issue!

Sonicrat told me to check the signal/ground and vref/ground voltages @ the TPS as well as setting it properly. I did that today with the key turned to on rather than starting it, because I figured it didn't matter. I got 0.8 volts for signal/ground and 4.0 for vref/ground, Sonic told me it should be ~1 and ~5 respectively. He said to try and start the car and see if it changes, did this and no change. BUT for ***** and giggles I decided to use the body as the ground rather than the TPS ground to see if it changed. Well it did! I got 1.0 volts for signal/body ground and 5.0 volts for vref/body ground. Sounds like a faulty ECU ground eh?

Not only that, but for some reason my SAFC was reading 100% throttle all the time yesterday, had no clue why, even at idle 100%. Well now it's reading properly! 0.0% at idle and goes up accordingly.

I'm going to go warm up the car now and check timing again to see if it's correct with a properly working TPS (while it still is of course). If timing is correct I think the problem has been solved, just need to redo that ECU ground.

RotaryEvolution

iTrader: (30)

heh, sometimes i wish the sensors were adjustable to obtain a smaller split, 0 degree split is not good for power but a small tuned split is better than the factory split from the yellow mark to the red, i forget what the difference is but reading some posts by Judge Ito he said you can get significant gains from tuning the split.

thank god for standalones.

ddub

Yah it almost makes me wonder how much I should care about fixing this entirely, I mean I'm building a new motor and going standalone with a new known working tps, so....

But I just need to fix the grounding issue and all should be well, hopefully.