Background:
Car: 1996 Miata, 01 Miata VVT engine, with Reverant built MS3 Basic
Some slight history: Had lots of trouble last year with noise, etc, most of which turned out to be a grounding issue with the Innovate LC1 wideband being grounded to the supplied grounds through the ECU. I changed to an LC2, and moved the grounds off the ECU and that fixed all the noise problems. I also sent the ECU back to Reverant to have him look at it because during autocross runs it would randomly freak out and eventually shut off (https://www.youtube.com/watch?v=lADmhL48Drg). Since fixing the grounding problem, it hasn't done it...until two weekends ago.
Two weekends ago: Drive the car to autocross perfectly fine. Couple hours later (2nd run group), I go to pull the car in grid and it goes nuts. It will barely idle, and giving it any gas will shut it off. The tach bounces between ~1500 and 0 as it loses and gains sync. Or course I don't have my laptop on me, though. I change the cam sensor in grid because I have a spare; no change. I give up and drive someone else's car. End of the day, I start it up and it's perfectly fine and drive home without issue.
That week: Change the crank position sensor and make sure it's gapped correctly. Car runs great, and actually feels a little bit better. A stumble that was happening around 2000rpm disappeared. Weird, but ok...maybe that was the problem all along. Drove it ~30 miles Friday night and it was great.
Saturday: Drove it to autocross, still great. Ran two drivers in the 2nd heat in the morning, first and 2nd fastest times of the day. Park it through lunch and the first afternoon heat. Start it up to go to grid and it does the same thing as last weekend. Ugh. I brought my laptop with me this time and took a composite log.
The cam, crank, tps, are all from the 01 engine. I'm going to look at the wiring (again) tonight...but I don't really think that's the issue.
Any insight as to what I should look at/change/buy/replace would be amazing. I'm at a total lost as to what to do. I can upload the tune when I get home from work, but here are the logs.
Losing sync; noob that's lost
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jeffmarsh750
- Experienced MS/Extra'er
- Posts: 301
- Joined: Fri Nov 23, 2012 3:17 pm
Re: Losing sync; noob that's lost
You figure it out yet ? Are you using factory sensors ? even factory from a few years previous should be perfect. Shielded wires ? Shielded plug wires ? Let us know.
Fastest MS powered vehicle on the planet ! 6.60@208mph
Re: Losing sync; noob that's lost
No, I still haven't figured it out.
I've also got a thread going at MiataTurbo that has people stumped as well
http://www.miataturbo.net/megasquirt-18 ... ane-85036/
The cam and crank sensors are new since the problem occurred the first weekend. They are factory '01 sensors. OEM Mazda coils. I don't think the replacement wire is shielded, but it's basically identical to the OEM wiring (gauge, etc).
The best a couple friends and I have found so far, is that when it gets into its state of not working...switching the ignition to falling edge fixes the problem. But then the VVT stops working (it has no idea what the angle is). It also doesn't like to start with it set to falling edge. Base timing is adjusted accordingly when switching.
I've also got a thread going at MiataTurbo that has people stumped as well
http://www.miataturbo.net/megasquirt-18 ... ane-85036/The cam and crank sensors are new since the problem occurred the first weekend. They are factory '01 sensors. OEM Mazda coils. I don't think the replacement wire is shielded, but it's basically identical to the OEM wiring (gauge, etc).
The best a couple friends and I have found so far, is that when it gets into its state of not working...switching the ignition to falling edge fixes the problem. But then the VVT stops working (it has no idea what the angle is). It also doesn't like to start with it set to falling edge. Base timing is adjusted accordingly when switching.