gcross

I realize there are a number of posts on this general topic… I’ve read through all that I’ve found and I think my problem may be unique. I’m hoping the experts that contribute to this forum can help point me in the right direction.I’ve just swapped a junkyard VVT engine with 42K miles into my ’94. Previously it had a ’99 head on a ’97 block with an MS2PNP ECU but the bottom end eventually needed a rebuild and I ended up going this route. I kept the VICS intake and my fuel rail/regulator and injectors from that engine and performed the classic VVT swap that’s nicely documented on this forum. I’m using the stock NB 4-tooth crank trigger wheel and '01-'05 COP setup. Cam and Crank position sensors are new.The VVT is currently not wired and I’m debugging using my MS2PNP… after I get my startup problem sorted I have an MS3PROpnp to swap in for VVT control.

My issue is that it’s almost impossible to start. Often I get no sputtering at all, sometimes it sputters but won’t catch, sometimes it repeatedly sputters and almost starts, and finally I have succeeded in getting it started a few times. Once it’s running it idles and revs fine and I was able to put a timing light on it and set the trigger angle offset. But when I turn it off, even after warming it up I’m back to square one.I’ve attached my current tune, a data log file captured while cranking and a composite ignition log. A few things I’ve noticed:

1. I’m getting a repeating 6-on/5off pattern of synchronization errors in the ignition log. I assume that’s not normal. In the data log the lost sych reason = 31, which I believe means “2 cams not seen”. The CMP and CKP signals individually look ok (I think).
2. The RPM signal in the data log oscillates between 0 and ~250. Maybe that’s a side effect of the synch losses?

Some things I’ve checked while debugging. Some of this was done before I got it started the first time:

1. Timing belt is set correctly per instructions in the online 2005 Miata Service Manual. I went back and double-checked this even though I was sure I did it right the first time.
2. Ignition Input is “falling edge”, spark output is “going high”
3. Crank trigger wheel is not installed backwards. I physically checked but I don’t see how it could run if it was flipped anyway.
4. CKP sensor gap to wheel tooth is 1.0mm
5. Checked continuity on the coil and sensor wiring changes back to the correct ECU pins. All good.
6. Verified spark and injectors in test mode
7. I did the VVT actuator and solenoid checks listed in the Service Manual. The actuator was correctly oriented on the cam gear and I couldn’t turn it by hand when installed on the cam.(I could jiggle it very slightly but assume that was a small amount of play with lock pin) The solenoid defaulted to fully retard position when no power was applied. I did not take the actuator itself apart.
8. My fuel lines are not swapped. I can hear the fuel pump when I turn the key on. I can smell fuel if I do extended cranking and have checked/seen fuel at the plugs. Beyond that I haven’t done any additional fuel debugging, but fuel delivery was working fine before the swap and hasn’t changed.
9. One oddity… I had to set the trigger angle/offset to 11 deg to get the timing light to match the fixed offset. Is that an unusual amount of adjustment?

Again, when I have gotten the engine started it seems to run fine and the synchronization errors disappear. That would seem to eliminate a number of potential causes. Thoughts and questions:

1. Could my VVT actuator be screwed up so that the cam isn’t defaulting to full retard? Seems unlikely but I’m starting to wonder if this could be the issue.
2. Is there a compatibility issue with MS2PNP and the VVT engine (aside from not being able to control the VVT) or a settings issue? I’m no expert on any of this. Current tune attached.
3. What am I overlooking?

I appreciate any suggestions… I’ve been beating my head against this for awhile now and its starting to hurt.

hector

I don't understand why it won't run now when it ran before? Were you using the NB1 sensors when running the NB1 head? They are the same sensors and the only thing that changes is the cam sensor location. Did you have to extend the wires for the cam sensor? If so, I would start there.

If you were using the NA ignition on the previous engine, then that's another matter altogether. In that case I would try switching the ignition capture and/or spark output.

gcross

It will run now, its just extremely hard to start.
When I had the BP4W head on the '97 block I was using the NA CAS, so yes, I had to extend the wires for the VVT cam and crank position sensors. I've double-checked my wiring and my ignition log shows that I'm getting a good signal from both (I think) but I am getting a bunch of repeating sych errors.

gcross

Oh, and for settings:
ignition capture = "Falling Edge"
spark output = "Going High"
I haven't played with these but everything I've read indicates these are the correct settings. Should I try something different??

hector

If your wiring is good then it very well could be the TS settings. Either that or the pull ups may not be right. Maybe the MSPNP is set up for the NA CAS and the pull up resistors required for that are different?

gcross

The MS2PNP is a '94-'95 version so it was certainly set up for the NA CAS initially. I changed the Spark Mode from "4G63" to "Miata 99-00" when I installed the VVT. I did wonder if pull up resistors are required. Maybe someone can answer that? If so, would they also be required with a '94'-95 MS3pnpPRO?

hector

I don't remember now since it's been so long but I believe when I went to NB sensors on my VVT swap with my DIYPNP which is MS2 I did have to do something with the pull ups. But I was sharing the signals with the vvtuner so maybe that had something to do with it.

And when I went to MS3promodule, I definitely had to change the pull ups. I have a 1k to 5v on the MS3 on both cam and crank.

I don't know if the DIYPNP and the MSPNP2 share the same hardware but maybe compare the pull ups/ignition settings between the NA and NB on the DIYPNP documentation.

gcross

Eureka! I dug into the MS2 Hardware manual and found that it recommended using Ignition Capture = "rising edge" for Miata '99-'00. I made that switch and viola! The engine now starts right up every time. I feel foolish for not trying this sooner.

That done I reset the timing and my trigger wheel offset is now +6 degrees instead of +11.

I didn't install any pull-up resistors and so far, so good. We'll see if I have any future intermittent issues in that regard.

Thanks for the suggestions Hector, they helped point me in the right direction!