Tach sits at 500 RPM when off

[vex]

The Tach sits at 500 RPM when the engine is off (key in the off position). Regardless of what location the key is in (off or acc) the Tach still sits at 500RPM. This is a recent development as prior to about a week ago the Tach would sit at 0 RPM when off. It reads correctly while the car is on and running (verified via RTek2.1 pocketlogger software). Any suggestions on how to remedy this situation?

[vex]

I need to correct something: It appears that my Tach is off all the way through the RPM band by 250 RPM (it's hard to tell when you're driving and trying to look at the Tach and the Read out). This makes sense since the needle sits at 500RPM (which is really only 250 RPM value off of zero). So the question is this: What do I need to do to reset the needle back to 0 and thereby fix my inaccurate Tach?

[WE3RX7]

I made the earlier suggestion regarding power/grounds, etc... but I'm thinking that is not the case (as you've already tested this and proven it not to be the source of the issue).

I'm now wondering about the RTek causing the issue though?? I'm assuming you had to tap into the blue/yellow wire for the tach signal for the RTek reader - or is it just reading it from the ECU directly?

The signal is usually a pulse and if there was something messed up with stock wiring system/coils, etc it would cause your tach to bounce, not just sit at a steady 500RPM, so it would seem that something in between your coils/ignition system and the tach would be TELLING the system 500RPM. And since the only thing in between is the ECU/RTek - I'm wondering if thats the problem. I'm not familiar with that version of the RTek and what settings it may have, but I'm curious if you've made ignition setup changes/adjustments against the stock settings??

Just trying to stir up some ideas....

[vex]

Originally Posted by WE3RX7

I made the earlier suggestion regarding power/grounds, etc... but I'm thinking that is not the case (as you've already tested this and proven it not to be the source of the issue).

Yeah, I tested that idea. I seem to recall that the issue started when I was trying to start the car and turned over the engine while the fly wheel was still turning. Aka: Tried to start the car, wasn't happening, let off the key before the fly wheel stopped I tried turning it over again (didn't grind gears or anything) but I seem to remember the needle doing something funny right when I did that.

I'm now wondering about the RTek causing the issue though?? I'm assuming you had to tap into the blue/yellow wire for the tach signal for the RTek reader - or is it just reading it from the ECU directly?

It comes directly from the ECU, no wires are taped. It uses the stock harness.

The signal is usually a pulse and if there was something messed up with stock wiring system/coils, etc it would cause your tach to bounce, not just sit at a steady 500RPM, so it would seem that something in between your coils/ignition system and the tach would be TELLING the system 500RPM. And since the only thing in between is the ECU/RTek - I'm wondering if thats the problem. I'm not familiar with that version of the RTek and what settings it may have, but I'm curious if you've made ignition setup changes/adjustments against the stock settings??

Just trying to stir up some ideas....

I think the problem may be that for whatever reason the needle just got shifted 250RPM up (which would cause it to sit at the 500 RPM mark when off, and display the 250RPM discrepancy throughout the powerband). I'm wondering if it's just the needle shifting or if the motor is actually out of calibration and needs to be re-calibrated/reset. If it's the latter what do I need to do to do it? if it's the former, will I just need to remove the cluster and break the cluster down to manually move the needle to zero?

[WE3RX7]

I dont believe there is a "reset" option honestly for the tach. If it happened during the starting incident you referred to above its possible something did get "wacked" out. Do you have an extra tach laying around? I'd tap it into the tach wire coming into the ECU (the blue/yellow wire) and make sure that the signal going TO the tach is correct before manually breaking down the cluster and resetting the needle.

However, a simple though is that if the tach is electric (gets an electric signal from the ECU) and you disconnect the battery and the tach still sits at 500 w/ no power going to it at all - that it is probably just out of wack for whatever reason and will probably just need to be manually pushed back down, lol...

[vex]

Originally Posted by WE3RX7

However, a simple though is that if the tach is electric (gets an electric signal from the ECU) and you disconnect the battery and the tach still sits at 500 w/ no power going to it at all - that it is probably just out of wack for whatever reason and will probably just need to be manually pushed back down, lol...

That's what I'm thinking it is. I'm pretty sure I've disconnected the battery and it still sat there. I'll try again and if it doesn't move I'll just have to break it open and push it down.