Diagnostics help, please - sputtering, crazy tach signal

[opethmike]

For the last few weeks, I have been having some issues with 1049 that are making the car near unusable. The following things happen:

1. When I go wide open throttle, or heavy throttle, the car will sputter real hard, almost as if hitting a rev limiter (which I don't have set). It will do this usually between 3,500 and 4,500 RPM.

2. The AFR will oscillate widely from lean to rich to lean, etc. As you can imagine, the car doesn't exactly drive smoothly when that happens.

I have observed in the data logs that I have examined that when these things are going on, that the RPMs that Megasquirt is reading/TunerStudio is displaying will jump around wildly. The dash tach does NOT - it stays steady.

I've tried some of the Tuner Studio noise filter seemingly to no difference. I've also checked the wiring where I get the inside of the car (white/slate which normally goes into the idle ECU), and at the ignition coil end. Soldering/crimping all look good.

I'm at a loss, so any help would be appreciated. My current tune file and a data log from a drive tonight are attached.

[Bitsyncmaster]

Sounds like the EFI ECU is getting a noisy tach signal. So if yours was working and suddenly started this problem, I would first check the ECU for a bad solder joint and or burned component (cap or diode). Is your alternator voltage running normal? Is your battery getting old?

[Spittybug]

I just looked at your files Mike... You are running fuel only? (look at the tach/ignition settings tab). I though you went full control..... So your timing is still dizzy controlled - funny, I don't know why when I loaded your .msq into the megalog viewer it popped up a spark table too??? Yet I can't see one when looking only at your .msq file in tuner studio.

Can you confirm?

[opethmike]

I just looked at your files Mike... You are running fuel only? (look at the tach/ignition settings tab). I though you went full control..... So your timing is still dizzy controlled - funny, I don't know why when I loaded your .msq into the megalog viewer it popped up a spark table too??? Yet I can't see one when looking only at your .msq file in tuner studio.

Can you confirm?

Owen,

I am still running fuel only. Confirmed.

-Mike

[opethmike]

Sounds like the EFI ECU is getting a noisy tach signal. So if yours was working and suddenly started this problem, I would first check the ECU for a bad solder joint and or burned component (cap or diode). Is your alternator voltage running normal? Is your battery getting old?

Battery is about five months old. I haven't checked voltage with my DMM yet, but the dash gauge and the tuning software both show ~14 volts while running. I'm VERY rookie at looking at circuit boards, so I'm not quite sure what to look at there, but I will follow your suggestion and see if I can find anything. I'll also hook it up to the simulator board that I have to see if the tach gets funny then.

Thought/question - I could be wrong, but it SEEMS that this problem starts happening/gets worse when the car has been running for a while. Maybe a bad solder joint on the ECU board is loosening up when the ECU warms up from running?

[AdmiralSenn]

How are you getting your tach signal? Gray/white wire from coil negative? Are you using the VR conditioner circuit or the hall/optical circuit?

My first few attempts to tune Christine yielded horrible noise on the tach signal. I pulled a new tach signal off the distributor lead and used the VR circuit to condition the signal and my tach input is probably about as clean as they get on these cars.

[opethmike]

Coil negative. I have the 3.57 box from DIYAutoTune as it comes, I have not touched the insides of the box. The car has run without these issues for about a year and a half; they are a few weeks new.

[opethmike]

Also to note, I've tried three different ignition coils, and the issue was the same. So I seriously doubt a coil issue. Right now, I have the tach wire from the MS relay board soldered onto the grey/slate wire. To eliminate that wiring circuit as a cause, I am going to try running a wire from the MS relay board directly to the coil negative.

If that still has issues, I would have to think that something is wrong with the MS unit, but I don't know how to test that.

[Spittybug]

Also to note, I've tried three different ignition coils, and the issue was the same. So I seriously doubt a coil issue. Right now, I have the tach wire from the MS relay board soldered onto the grey/slate wire. To eliminate that wiring circuit as a cause, I am going to try running a wire from the MS relay board directly to the coil negative.

If that still has issues, I would have to think that something is wrong with the MS unit, but I don't know how to test that.

Do indeed try running directly to the coil. I vaguely remember when I was having my issues converting that there was a difference in where I grabbed the tach signal. Although it is odd that it should just stop working properly...... Could be something else in the car that has "changed" in some way and is now creating noise.

[Bitsyncmaster]

Another long shot guess is that capacitor on the coil could have gone bad. It's good you tried other coils.