tach signal drop out

[hemidart]

I have good tach signal at idle but drops out at 1200 rpm until engine reaches normal operating temperature. After warm-up, tach signal is fine at all rpm's up to 6500. What could cause this?

[Matt Cramer]

What exactly are you using for tach signal input on this car? Different types of signals can have different issues.

[hemidart]

I am using 36-1 DIY wheel with a ford vr sensor

[Matt Cramer]

Is the sensor wired directly to the MS or are you using EDIS? Also, what main board do you have?

[hemidart]

I am using a 3.57 board with the sensor wired directly to the tach input.

[Matt Cramer]

Ok, I would try adjusting the VR trim pots then.

[hemidart]

I tried adjusting the pots this did not help. If I go to far,it Iooses the signal during crank. When the RPM comes up fast enough the signal comes back at about 2500 RPM. Do you have any ideas?

[Matt Cramer]

Any chance wiring the sensor the other way would work?

[hemidart]

When I wire it the other way it has no signal at all.

[Matt Cramer]

Try adjusting the sensor for a closer gap.

[hemidart]

Have adjusted from .020-.120 with no change if I go over .120 it looses signal. Currently set at .040.

[DonTZ125]

You may have a bad sensor. Cold, it has an intermittent (internal) contact. Warm, it's flexy enough to move with the engine vibrations.

[hemidart]

Installed a different sensor. No change, found that signal still drops at 1200 rpm when I restart the engine at normal operating temperature for about 30 seconds.

[Matt Cramer]

Do you have access to an oscilloscope? If you do, I would try using that to examine the signal from the sensor.

[8974Ollie]

Have adjusted from .020-.120 with no change if I go over .120 it looses signal. Currently set at .040.

0.020 inch is still too much gap it needs to be 0.010 or less.

[hemidart]

I do not have acess to a oscilloscope. Tryed moving sensor in to .010 this did not help.

[Random Hero]

I'm having a similar issue with a VR sensor, MSII w/ v.2.890 and 3.57 board smd style assembled by DIY. Running EDIS.

Tach signal will drop out randomly, from a steady idle to 0. Today it dropped out enough to put the MS back into warmup and afterstart enrichments.

VR sensor wiring is thoroughly shielded.

Not trying to thread-jack, since we have a similar issue perhaps we can find a solution together.

Also, no idea why the wideband is going so freakin crazy, seems to be unrelated to the rpm issue. On the log you can see where the rpm signal drops out quite a bit, but where it fell out and got back into ASE is around 436 sec.

Have tried moving the sensor's gap to the 36-1 wheel, doesn't seem to change.

Here's the log.

[hemidart]

My signal only drops out until the engine reaches normal temp and it is in warmup after that it works fine. On restart the problem only last a few seconds.

[Random Hero]

Well, we got a different EDIS module and installed it and the problem disappeared for a while. Tach signal does not drop out at all at idle any more like it used to. I was doing some driveability tuning around the neighborhood and made a short boosted pull in 3rd and the tach signal dropped from 3300 to 0 in .3 seconds and stayed there for about .7 seconds until returning to normal.

Not sure where to go from here. The module is not new, just another used one. The problem seems to be intermittent, we were making WOT pulls a lot yesterday and had no problems.