VR sensor problem?

[Rob_B]

This is an old topic, but I added new info in the 8th post

I think I have a problem with my VR sensor. But can't pinpoint it yet.

The car runs fine on the MS1 with hi res code and using wasted spark. But starting isn't great. Every now and then it kicks back during crancking or hear plopping sounds from the exhaust. I have checked the ignition timing a few times and that is spot on. (while running and during crancking)

To me it looks like the VR sensor isn't reading all the tooth on the 36-1 wheel at very low revs and that is why it isn't triggering at the right time.
The sensor is centered on the wheel and I have adjusted the gap a little a few times to see if that helped.

Because it doesn't always do it, I haven't been able to take a tooth log showing anything when it happens.

Any idea what this could be? Is this some thing that could be adjusted with the R52 and R56 pots?

Thanks.

[904svo]

Run Tuner Studio, Diagnostic, Tooth logger and you will see if your VR is out of tune
out of tune.

[Rob_B]

I have tried that but the problem doesn't happen every start. So I haven't been able to log it when the problem occured.

[preludefan]

is your setup trigger return or time based?
i have a hall sensor based wasted spark system that is set to time based cranking and every now and again it tries to kick the engine the other way when cranking, but its no big deal to me.
also, once i had the random wrong timing speaking going on, the timing light was not flashing in sequence either- turned out to be my spark plugs which were grounding out at random- i installed a different type and the problem went away totaly.

this may sound silly to you, but it fixed my problem- sometimes vr sensors are blamed for alot of random things that happen elsewhere


good luck

[Rob_B]

I started with trigger return and changed that to time based. I think that made it a little better. But it wasn't gone yet. That is why I started this topic.
Before that I had changed most of the ignition system, including the sparkplugs. (changed from Bosch to NGK's)

[Rob_B]

Not sure if I see this the right way. But it looks like it is triggering to many times at the wrong time during cranking.
I have set "Hold Ignition" at 4 and only noticed now that it doesn't do that most of the time. Looks like it counts the false triggers too and that make the engine start at the first turn most of the time.

Still haven't had time to check any thing on the car yet. But this is some thing I thought about when looking through the msq.

[904svo]

Just for kicks, turn the VR sensors leads around and see what happens.

[Rob_B]

Finally got around try a few more things. It took a little longer than expected because the car hasn't been used for a long time.

Tried changing the wires around on the VR sensor without any luck. (made things worse) And tried a different VR sensor (from a Ford this time) and that changed nothing.

But today I got a tooth log when the problem happened. No starter kick back this time. But a little backfiring an plopping in the exhaust.
The first picture is while cranking and the 2nd at idle. Does MS see this as more than one trigger? And is that causing the problems?
And ifso, how could I fix this?

graph_cranking.png

graph_idle.png

[Rick Finsta]

Try moving the sensor closer to the teeth to see if you can up the voltage of the VR sensor during cranking and find a way to get more RPM during cranking to get rid of the lope pattern.

[Rob_B]

I have tried moving the sensor closer without success.

But what is the problem here? Is MS seeing the high signals when the crackshaft is turning faster as missing tooth?

[Rick Finsta]

I would imagine, yes. It would actually be when it is turning more slowly, though, not faster. Those bars are taller the longer the time between signals, so the slower the wheel is turning (or the larger the gap, as with the missing tooth) the taller the bar on the graph.

Perhaps you can go to a (n-2) wheel to get the time for your trigger signal even higher compared to the others? Or perhaps rephase the trigger wheel, so that the whell is turning the most slowly when the missing tooth passes, causing the event to be the tallest by a wide margin?

I hope someone else chimes in on this to correct me if I'm wrong...

[Rob_B]

You are right. The lower signal is when the crack is turning faster.

I have been doing some searching and found this reply in THIS topic.

That's the problem...
the high compression is making the missing tooth indistinct. Take a look at the tooth log and compare it to the examples in the manual. By eye the tall missing tooth is quite unclear and is not double the length of the tooth that follows it due to the compression slow-down.

Two ideas, you might want to do both.
- rotate the trigger disc so the missing tooth region is 2-3 teeth earlier (that will put it in the high-speed "dip" in the tooth log)
- remove one more tooth to make it a -2 wheel (remove the tooth that would pass the sensor before the missing region)

For either of these changes you'll need to re-set your tooth#1 angle.

Removing the one tooth (the 35th) would put the signal right in the middle where the crack is turning fastest.
But would this work with MS1? Removing one tooth is the easiest thing to do on this engine, but there is no way back.
So I would like to know if this works. Does MS1 work with a 36-2 wheel?

[Rick Finsta]

TunerStudio allows for a 36-1 or 36-2 pattern, at least in the current beta I am running. I've seen James (or one of the other gurus) recommend the switch to a -2 tooth wheel. So long as you can phase it so as to not have issues triggering on either missing tooth, you should be fine.

If you've got a JimStim, it has a "32-2 Harley" wheel pattern (which is 34 teeth, then two missing) you could use to test it first.

[Rob_B]

I have taken out an other tooth to make it a 36-2 wheel. Changed the Wheel Decoder settings and checked the timing again.

But the problem is still the same.

Most enigine starts are fine. But often at cold starts or some times when the engine is warm, I get a back fire or starter kick back.
Also the "hold ignition" setting doesn't seem to work many times. Than the engine fires at the first turn of the key instead of holding for 4 cycles.
To me this looks like the MS is getting false triggers for some reason. And that is messing things up.

I'm going to try it with the starter disconnected from the rest of the car and start it with a 2nd battery. That should rule out noise from the starter.

[TTC]

I had this exact problem. Turned out it was a combination of unstead voltage and noise. I put one of those old car stereo noise suppressors on and rewired the ecu power using a painless wiring kit. All those problems went away. Then a few years later new ones showed uplol.

[Rob_B]

Thanks.

I fitted a noise suppressor in the 12v feed to the ECU and so far haven't had the problem again.

It is more like a band-aid than a real fix. But atleast now I know where to look and in the meantime I don't risk damaging other parts.

[TTC]

Glad it helped