Guys, trying to sort out an intermediately-cold starting issue with my newly acquired turbo 1.8 NA (1.6 harness). Meaning, it'll start when completely cold (with a bit of gas, and sometimes a good number of cranks), or fully warmed up. But if I've just started car from cold and only let it run a few seconds before shutting down, it won't restart at all no matter how much cranking, finessing of the throttle to try to catch it, or how I'm holding my tongue. When starting from cold, I have to manually step up the idle (~1300 or so?) with gas pedal until it warms up a bit and I can ease my foot off and let it settle into a nice solid idle at a hair under 1100. And when it does start from cold, there's a bigass cloud of unburnt fuel that makes its way out the back, but clears quickly. When I changed the oil right after I bought the car, it had a strong gas smell to it, so I know this long cranking thing has probably been going on a while (which is probably why the starter was burned out, which is why I got it pretty cheap...).

Once started, it idles and runs very strong.

A few points to consider:
- spark is strong and it's getting fuel (too much fuel? maybe). Compression is exactly 170 across all cylinders
- Coolant temp and air temp sensor readings look reasonable in TunerStudio. Spark advance shown at 15 degrees. Christ, that seems high. Have not confirmed actual advance (have COPs, so need to track down some scrap plug wire so I can get my timing light on plug 1, right?)
- the car doesn't appear to have a TPS or IAC hooked up (see pic).
- beyond that, wiring is very similar to what's in the pinout in another attached pic (props to whoever made the diagram - it's been super helpful), except that the pin 31 and pin 36 ignitors are switched
- AFR, as read by MS1, is about 0.9 more than what's shown on AEM UEGO wideband gauge on dash. O2 sensor is shared, with the gauge outputting to the MS1. Car seems to run pretty rich

A few resulting questions:
- Regarding unhooking the TPS and/or IAC - is that common for guys to do? Besides not being able to trigger flood clear mode (set at 250 in TS), I'm sure there are other reasons the ECU needs to know TP? And without IAC, I'm guessing there's no way to tune in a higher idle until warmup, since there'd be no way to get the additional air past the throttle body. So much of the build seems to have been done by the PO according to the mt.net bible that I'm assuming the deletes were done with this forum's blessing, but I can't seem to find any mention of deleting TPS or IAC.
- Should I try to get ECU AFR to match what's on the dash? Is there a way to manually calibrate (I selected AEM 30-42XX option in project properties)
- what could be causing car not to start if temp is in an intermediate range? Something with the wamup wizard or ASE settings? I bet I could post a screenshot of one table or another and you gurus would spot the problem in like 2 seconds.

Thanks in advance, guys!

 

Try increasing your cranking rpm to 400 or so. 300 is a bit low, and it may be why it is struggling in the cold. You can also play around with some startup settings like batch fire during cranking, your injector pw etc. You may want to data log your car dying and when its not starting so you can narrow down the problem. If your IACV is in fact deleted, then you basically always have to manipulate the throttle on cold starts (which it sounds like its deleted.)

 

Thanks Herbst - good ideas! In regard to the cranking RPM (and I could be totally wrong here), I guess I was under the impression that the starter's gonna crank at whatever it can (regardless of value in that box), but once RPM exceeds the designated value, the ECU considers the engine to be running. Either way, wouldn't hurt to play with bumping it up. I'm a little nervous about playing around with the other settings though. There's a pretty good diy autotune article about "dialing in the MegaSquirt startup sequence", but it's not application-specific and I didn't want to be the monkey with the typewriter trying to write Shakespeare.

Any way I could get a quick gut check on the existing values in my startup tune?

Thanks again!

 

Yeah thats the right impression, by increasing it, you're trying to keep the car from dying when it does go under 400 rpm. As long as the rpm is over that set value, then your car is running normally. And its okay to be nervous. Just remember to save all your settings separately, and then you can fine tune your cranking and idling settings. Its pretty hard to blow up your motor when cranking and idling, so its great to learn how to adjust and manipulate settings without a huge amount of risk. I for one have learned alot from just tinkering with everything. I also have a little difficulty when I first begin idling because I deleted my IACV, but if my car dies it starts right back up, which is my main concern with your problem. It also looks like you don't have tps connected, which can be a huge help in tuning if you hook it up. If you want, upload your tune and some data logs and Ill see if I can help.

 

Herbst - thanks buddy. Tune attached (hah, I think?) and I'll try to get a data log tomorrow. Did I attach the right kind of file?

I'm on MS Lite, which I think will get me like 8 seconds or something of logging.

 

You may have to adjust your injector deadtime. You're at 1.2ms @ 14V. Look at this thread https://www.miataturbo.net/ecus-tuni...ad-time-56061/ Also you have a secondary fuel load enabled on speed density, unless you're using it, I would disable it. If it was me, I would try increasing the cranking rpm first and see how that goes, if the problem still persist I would try batchfire while cracking. And its always nice to make sure you have the correct injector timing, unless you're already sure that is what its suppose to be.

 

Herbst, thanks again for taking a look! Will tweak this evening and report back.

Still a little curious about why the PO would have unhooked the TPS and IACV? Easier to set everything up if you take them out of the equation? Brain, if you stumble across this thread, I think the MS1 was built by you - any insight would be helpful!

Otherwise, I might see about learning how to get everything to work with them hooked back up.

Thanks!

 

When I started figuring out how to get everything running, I turned off every feature that was not nessisary to run the engine. So I can understand why they would be unhooked.

 

"Mathew 15:14" was going to be my comment for the jpbro / Herbst conversation.

jpbro, I call @Braineack for you.

 

he had no idea how to tune and was lazy?

MS1 doesnt run idle control incredibly well, but its better than no idea control at all. and not using a vTPS when you have one is silly. TPSdot > MAPdot.

 

Lol, before I looked up Matthew 15:14 I had a feeling it was something about the blind leading the blind. Was not disappointed.

DNMakinson, thanks for giving Brain a holler, and Brain, thanks for the confirmation that I should be able to get it all going again.

 

Guys, thanks for all the insight. Wanted to follow up with the solution.

Ended up that PO's cranking PWs were WAY too high, given my ID 725cc injectors, 4.2 req fuel, and 1.2ms injector opening time. Just as an example, PWs were at 9.5 to 8.4ms for 40-80F (respectively), and I knocked them down to 4.2 to 3.2 for that same temp range (of course, adjusted the entire range accordingly). Starts first or second crank now, although I probably need to fiddle with 160F PW, as it doesn't like to restart immediately after I shut it off. Obviously, the flooding explains why the oil smelt like gas when I changed the oil the first time, and why the car would kick out a huge white unburnt gas cloud if/when it'd finally fire up. Also explains why the starter was dead when PO sold it...

Ordered the newer pigtails so I can hook my 99 throttle body's vTPS and IAC into my '91 harness and start working on moving to TPSdot AE and not having to finesse the throttle for warmup.

I've never had to have a laptop in my tool bag before, so learning curve's steep - but you guys are big helps. Thanks again -

JP