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Old 01-29-2009, 10:38 PM   #1
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Default Tach Signal Suddenly not matching?

I know it is normal for the RPMs to read differently in megatune than on the dash tacho, but something isn't the same here. I've compared them before and they made sense. Today I noticed they do not match at all...which has to be bad but the car runs fine so far as I can tell.

Megatune reads MUCH lower than my car's gauge. at 2krpms on the car gauge, MT reads under 1500. As the revs rise, the gape of discrepancy increases. At 3200rpms on the car, MT reads 2200!

What could suddenly cause this? I'm completely baffled. My wheel decoder settings are fine so that cant be it. Resets are getting worse as well.

I just got home from class a little while ago, haven't done any troubleshooting yet. Not sure where to start, but i'm going to work at it tomorrow to get it figured out. Just looking for areas to start looking at this point.
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Old 01-29-2009, 11:31 PM   #2
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What one is right? Does it sound like you are turning 3200rpms or 2000rpms?

My guess its something with your stock tach. MS would be running rough or not at all if the tach was off.
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Old 01-29-2009, 11:34 PM   #3
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I've gotta trust the stock tach here...they were pretty accurate the last time I compared them. This seems to be a newish event. When i'm turning 3200 on the stock tach, it sounds like 3200.

I would expect ms to run terribly in this scenerio as well but it hasn't changed (yet).
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Old 01-29-2009, 11:45 PM   #4
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If resets are getting bad, you likely have an input problem or a grounding problem - both are kinda hell to fix. I imagine you don't have a oscope handy...

The stock tach suchs a bit, but not that bad. :-) I would guess you have a grounding problem to/in the MS if it's reseting.
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Old 01-29-2009, 11:46 PM   #5
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There's no chance you loaded an old MSQ or something and somehow changed the decoder wheel settings, is there?
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Old 01-29-2009, 11:58 PM   #6
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There's no chance you loaded an old MSQ or something and somehow changed the decoder wheel settings, is there?
No, there isn't because I noticed this while idling this morning before class. I checked the decoder settings while sitting in the car cause that seemed like the most logical issue to me.

As far as the resets, I thought I had fixed my grounding issue. I had no resets for several days the they started coming back. Now i'm getting **** loads of resets, they do not seem to effect the way the car runs though.
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Old 01-30-2009, 12:26 AM   #7
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If you had resets in the past, you may have been burning a msq and had one, which ***** the firmware. Reflash the firmware and put a FRESH (read, known good) msq. I had a power supply for my wideband go up in smoke and catch on fire while burning a msq. Riped out the wideband's power supply and the car was ok. I thought. After I turned it off, it wouldn't crank again. Megatune showed all kinds of crazy ****. Including a bogus tach.

Now I keep a few "backup copy-date" msq's so if I have a freak accident, I know I have one that works that I've never fucked with before.

HOW is everything wired? Explain in detail how all the grounds are done, how your wideband is wired up, etc. COPS? Need more info on setup.

Cliffs:
Redo firmware and put fresh msq
List your setup and grounding
Lose the big wheels

Synopsis- you washed your car and pissed off the MS. That's the real problem. Show it some love.
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Old 01-30-2009, 12:42 AM   #8
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Lol, first things first...16s are too big for my taste too...but I love my wheels.

Second, the car is stock. No cops etc. Grounds are as such:

MS - 2 16ga grounds run straight through the firewall to the IM grounding point (stock ecu ground on 1.6s). At the ms db37, there are 2 14ga grounds soldered to 3 pins each.

LC1 - Grounds are all running through the unused stock ecu ground. I've never had an LC1 issue so far. I installed it as per the instructions.

As for flashing the firmware, I think that is a great idea and i will deffinately be trying this tomorrow. I've done a lot of mucking around since the last flash. I'm going to do this and have also heard that spark plugs can cause weird **** like this so I may inspect those as well.
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Old 01-30-2009, 12:55 AM   #9
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Quote:
Originally Posted by wayne_curr View Post
Lol, first things first...16s are too big for my taste too...but I love my wheels.

Second, the car is stock. No cops etc. Grounds are as such:

MS - 2 16ga grounds run straight through the firewall to the IM grounding point (stock ecu ground on 1.6s). At the ms db37, there are 2 14ga grounds soldered to 3 pins each.

LC1 - Grounds are all running through the unused stock ecu ground. I've never had an LC1 issue so far. I installed it as per the instructions.

As for flashing the firmware, I think that is a great idea and i will deffinately be trying this tomorrow. I've done a lot of mucking around since the last flash. I'm going to do this and have also heard that spark plugs can cause weird **** like this so I will surely change those and gap them to .020" as well.
Try cleaning up the grounds, make sure all the stock grounds are hooked up and clean. Also clean the battery post at the battery. I've seen a member or two have crazy **** that ended up being a loose ground terminal at the batter. **** happens. Don't rule out the obvious.
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Old 01-30-2009, 12:16 PM   #10
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Quote:
Originally Posted by patsmx5 View Post
Lose the big wheels

And here I am picking up a new set of 16x7s this weekend to add to my 16x7.5s.



Just to rule it out, reflash your firmware and reload the msq. fwiw, my tach reads 7000 when I'm only around 6300. I have to rev on the stock gauge to about 8500 to see 7200.
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Old 01-30-2009, 02:09 PM   #11
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I did a test on the stock gauge, using the Jim Stim to generate the trigger signals:
AbeFM : photos : NB OEM Tach Response- powered by SmugMug
summary: I fed the tach known spaced tach pulses, and found that the tach is accurate at low RPM (1000), and from ~1500-~4000 is picks up linearly about 175 rpm of offset (it reads high). Then it stays there until ~7200 (reading ~7375) and by 7500 it's reading correct again, which it retains through 8000 rpm, which is as high as I tested.

Anyway, Pat had a good suggestion, reflash is in order. A side point - you want the LC-1 to reference the same ground as the MS - especially for the signal ground. I'd suggest running the signal ground to the block as well, this ensures you're not getting a 0.4V error in your wideband, and tuning all funny from it.

BTW - the ONLY time I had serious grounding issues, it was the LC-1 not playing nice with the MS, but I was taking switched power from the feed to the MS, so it's probably not your problem? Now I get it further down the chain, with bigger wire, though I've seen people use the fuel pump relay (I did this for a bit) and it really helped what I thought was a "grounding" issue.
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Old 01-30-2009, 07:58 PM   #12
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I'm trying to burn the new firmware using my stim but its not letting me. Haven't ever had an issue burning firmware in the past. It says:

!!Download failed: Expected Response "Boot >", but recieved this "!!"

Wtf?

This is my first time burning firmware on vista, is there something special I need to do?
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Old 01-30-2009, 08:35 PM   #13
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I'm assuming the boot jumper is correct? I don't know if there are special issues with Vista, it wouldn't surprise me. The serial port might not even work as expected. I'd ask on the MS forums if no one here has any advice.

Failing all that, it's a good sign things are messed up on the MS - that's where it checks the version before writting to it, to make sure you're not putting MS-II code on an MS-I.
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Old 01-30-2009, 08:37 PM   #14
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I'm assuming the boot jumper is correct? I don't know if there are special issues with Vista, it wouldn't surprise me. The serial port might not even work as expected. I'd ask on the MS forums if no one here has any advice.

Failing all that, it's a good sign things are messed up on the MS - that's where it checks the version before writting to it, to make sure you're not putting MS-II code on an MS-I.
Well, the boot jumper is not in, though did try it with the boot jumper which is pointless. I'm trying to burn regular HR10 code. No idea why it wouldn't work.

The MS responds normally in megatune with the stim so communication is working.
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Old 01-30-2009, 08:52 PM   #15
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Ok, got the firmware burnt. Just had the wrong com port selected, doubled checked what I was using in MT which was com 4 not 3.

Got a new BMW TPS wired up and ready to install when I put this MS back in. Maybe tonight, but the weather outside is frightful. Garage isn't heated.

Perhaps tomorow.
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Old 01-31-2009, 04:13 PM   #16
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I made an awesome garage heater by taking a turkey deep frier (just a propane gas burner) drilling out the holes a bit and T'ing it off the gas feed for the water heater. Sure, there's a 18" open flame in the garage, but it works awesome.
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Old 01-31-2009, 04:19 PM   #17
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I made an awesome garage heater by taking a turkey deep frier (just a propane gas burner) drilling out the holes a bit and T'ing it off the gas feed for the water heater. Sure, there's a 18" open flame in the garage, but it works awesome.
hahaha! gonna need a picture of that. Not a bad idea I must admit, i think i'll give something along these lines a shot. my garage is too small for 18" of flame though I think.
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Old 02-01-2009, 01:15 AM   #18
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It's not as bad as you'd think - the burner itself well sheilds it. Plus, if you ever take up smoking hookah, it's great for lighting coals, and takes much of the danger of getting sticky mess all over your kitchen out of home brewing.
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Old 02-04-2009, 02:42 PM   #19
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My dash tach isn't very accurate either. By the time I hit redline on MT (7200), the dash tach is somewhere around 8k.

Also, driving down the interstate with cruise control on, the dash tach will jump 200rpm once in a while. I'll look down, it'll be at 3800, then a minute later I'll look down and it will be at 4000. Then it will go back. Speed doesn't change. I don't catch it doing it very often, but it's quick when it does. Very weird.
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Old 02-04-2009, 04:49 PM   #20
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It's not as bad as you'd think - the burner itself well sheilds it. Plus, if you ever take up smoking hookah, it's great for lighting coals, and takes much of the danger of getting sticky mess all over your kitchen out of home brewing.

Ahh the joys of homebrewing. I always wanted one of those propane burners when I was brewing weekly. They make quick work of 5gallons of wort.

As far as the Tach signal, I'm not sure if it was reloading the firmware/msq or playing with my grounds but its working fine again and i'm getting fewer resets. Only had one on my last drive if I recall.
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