MS3 Intermittent RPM Issue
 

I've got a strange issue with my MS3, mostly because I'm a retard. It was working perfectly on the stim, but when doing a trial fit in the car I dropped the box about half a metre (2 feet) :facepalm:

Now when I hook it up to the stim, the RPM's act very strangely. No matter where the RPM pot is turned to, the RPM will sit at 0 but jump to where it should be about once a second. I've scoured the board looking for a cold solder joint, but everything looks fine. Given that I'm somewhat of an electronics noob, I've probably missed it.

Does anyone have any other suggestions what could be causing the issue, or which components to take a close careful look at? For reference, I built it using Brain's writeup here. If a log of what's going on would make things easier to diagnose, I can put one up, but I've still got to get my head around MLV.

If you could post a composite log - NOT a normal data log - of an attempted start, this will let us see which RPM related sensor inputs are and are not working.

I can't get an attempted start, I haven't built my harness yet (I was wanting to fix the MS before continuing the install). I can give you a log with the jimstim, it should still give you the sensor info you need?

I've attached an example composite log using the stim (set up for 4G63), which shows the RPM spike.

You've got problems with your cam signal, the top graph in the composite logger window.

Thanks! Well, aside from the obvious wires between TSEL and OPTIN and such, which components are involved in the cam input circuit? Worst comes to worst, I'll reheat the joints for all of them and see what happens.

On another train of thought, are there any components that can be damaged if the box is dropped? Just checking that I'm not supposed to be replacing something instead of hunting for a cold solder joint.

http://www.boostedmiata.com/gallery2..._0003_mods.jpg

Cam signal are the red lines on this picture, could be your pull up either shorting or not soldered well (you did put some heat shrink around it right?) Really, if you did everything right dropping it 2 feet shouldn't do anything.

Are you using the mods on the main board like Ian used, or the MS3X for cam sensor input?

I'm using Brain's mainboard mods. I found out last night that my housemate's left his soldering iron at work last week (which is inconvenient, because he started a new job THIS week), so I'll check back in when I've had a spare moment to buy my own and reheat those joints on the red wires.

So I've reheated those solder joints (and all the other wire solder joints), and it hasn't changed anything. I've carefully check out the cam input wiring, and everything seems fine. I can't see anything shorting with the pullup, and I get continuity across it (at 460 ohms).

I checked the composite logger again, and when I zoomed right out I noticed that the cam signal just seemed to be way too uniform to be a dodgy connection. Any other ideas for what's going on?

Bump - I've been trying, but I just don't have the electronics knowledge to figure this out myself.

Would the MSEXTRA forum be able to diagnose it, even though I'm using Brain's mods?

Pics of both sides of the board please. Good quality or they are as good as useless.

that doesnt look like the correct trigger wheel is selected.

These are the best I can do with the lighting I've got right now (it's dusk here). If you need a better view of something specific on the board, I can get a close up.

http://i897.photobucket.com/albums/a...5/IMG_4652.jpg

http://i897.photobucket.com/albums/a...5/IMG_4656.jpg

I'm pretty sure I hadn't changed anything between dropping the MS and discovering the issue (I had it working perfectly prior), but just in case, I have the Jimstim set up with DIP switches 2 and 3 on (for 4G63), the primary tach jumpered for a square wave signal (no idea if this is correct, but I think it is) and with the second trigger going to pin 25 (I1A). Here's my TS settings in case the error lies there.

https://www.miataturbo.net/attachmen...1&d=1299745725

These all look correct.

Yeah, I figured that'd be the outcome. It was working perfectly before I dropped it :vash:

I'll keep messing with it, and see if I can figure it out. I'm pretty sure it's a hardware issue, but looking at those TS settings again, I'm not so sure about the 'skip pulses = 3' setting (only because I have no idea what it actually does, and it sounds like it could be a likely candidate for a strange yet uniform cam signal).

I'm going to cross-post this to MSEXTRA tonight (I assume they have better knowledge for the hardware side of things), and if I end up finding a solution I'll report back. That said, if you guys happen to have any more ideas, I'll gladly hear them!

IF you dunno what something does, why not look it up in the manual.

skip pulses is the number of ignition pulses the MS skips before doing anything in order to calculate the RPM correctly.



But if that's the composite log you are getting with the ignition settings posted above, then something IS messed up for sure.

Well, jsmcortina at MSEXTRA figured it out. DIP switch number 2 on the Jimstim wasn't working, so it was giving a 36-1 signal instead of 4G63.

I can't believe that the Jimstim decided to go crazy at the exact moment I dropped the MS3, but crazy things happen huh?

Thanks for the help guys, I appreciate it.

FYI, my JimStim also flipped out on me for no particular reason. I trashed it and made my very own instead.