'87 TII Megasquirt idling issues.
 

So this is going to be kind of long, but I feel like I shouldn't leave anything out. Btw I did search and couldn't find any topics covering this, but if you know of one go ahead and hook me up with a link to it. I'll def appreciate it.
To begin i have a 87 tii with a S4 engine, bought it last year. Fast forward to now and i have completely rebuilt the engine (rear rotor had 60psi of compression), streetported it properly, stock primary inj. and 850cc secondary inj., stock turbo for now, MSX3 wired exactly to Aaron Cake's specifications. Full emissions, A/C, and power steering delete. And that's the main jist of it....
First issue I'm having is kind of irrelevant at the moment but the starter won't crank over fast enough to actually start the engine. So I have to pull start it every time it dies. I have my fuse block grounded to the engine and all of my starter wiring is good so maybe just a tired starter/worn out battery combo? Unless someone else has suggestions then i am all ears on that front. Oh and it cranks at around 220 rpm.

Second, and most prevalent, every time we have it running and start bringing down the idle it sputters and dies around 1500 rpm. Most of the time I can catch it and keep it running but I have attached a datalog of when this happens. So I guess my question is....why is it dying on me like this? and do any of you know what i can/should do?

So far this car has been a little over a year long project, mostly because of funds, and I'm about ready to throw in the towel. I have checked and quadruple checked all of my wiring, even swapped my CAS(was having lost trigger sync issues...#11, that's fixed now though), and I still can't figure this thing out. It seems no matter what we do it always dies below 1500 rpm. Any and all help is GREATLY appreciated. Thanks guys!

Looking at the datalog, I don't see an obvious reason why the car died. Sync loss counter doesn't increase.

AFRs look fairly rich at into the 11s. That won't help. Should be in the mid 12s. It will tend to drown out the engine.

How much runtime has this engine had?

Can you also post your tune file so that we can see what the tune is doing as the log is played?

i didn't look at the logs but i think i would do the following. its a choose your own adventure, so its fun.

1. raise the idle to like ~2000rpm.
2. start it, and let it run up to temp.
3. tune the 2000rpm spot on the map. at a free rev, you should be able to do like 14.7:1 give or take, and then you can play with timing to see what it likes, you might start at 15btdc, and try moving it up to 30 and see what happens.

now you have a choice. since it by now has run for some time, and runs well, you could turn it off and compression test it. these engines need to run ok to get a valid compression number.

or you can lower the idle to 1750 rpm and tune that spot, AFR should be the same as 2000. for timing you might start with a little less, but it still should be 20Btdc +/- 7

then i'd work it down to 1500, repeat tuning. at some point either the engine will break in, or you'll notice it running weird or something. with the stock ecu, usually you have a vacuum line crossed (the FPR one is a common mistake, only 1 nipple on the intake sees vacuum AND boost, so you can cross a hose, and the FPR only sees vacuum), or there is a vacuum leak or something.

then look at your map, and see if the 1250 cells look ok, and then try 1250rpm. at 1250 rpm, you are at the bottom end of what Mazda did in closed loop, so your AFR could be richer, maybe by 1/2 a point.

etc etc. my bet is that there is something mechanical that isn't quite on right, these cars have a lot of hoses and valves and gaskets and stuff, its not very common to have them all correct on first start.

Aaron I'll post up my tune when I get home from work today, and the engine has maybe 5 minutes on it, and j9fd3s I'll give that a shot....I kind of figured I was trying to idle it too low for a fresh rebuild so I'll start at 2k and work my way down.

i am thinking there is something dumb that isn't on correctly. these things are complicated, its pretty rare to not have something right on a first start.

we can't really point you in a good direction, except for the map, so maybe we work on what works?

Sorry guys I've been swamped at work and haven't had a chance to upload the tune or touch the FC. I'll get to it as soon as I can which will probably be this weekend. Thanks for the support so far guys, it's def appreciated

The first thing I'd look at is compression. A long time ago I had a rebuild with low compression and had exactly the same symptoms. I had to rebuild the motor better. It was my first try and I was poor so reusing the old but within specs apex seals!

Depending on the condition of the housings and the seals used, the engine could have rather low compression for the first few hundred K. That is a factor as well.

One of the things I do on fresh engines is as soon as I'm sure nothing is leaking or on fire, I set the idle speed to about 2000 RPM and then just let it run 20 minutes or more while I walk around and check stuff. As well as adjusting AFRs so that the ratio is reasonable. It beds in the seals.