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View Full Version : V2.2 Board with bad RPM signal


guywithFX
05-17-2006, 02:55 AM
I have a V2.2 board running MSnS-e 29q firmware and it has a "bad/buggy" RPM signal. Originally when I built the board the RPM displayed fine when used with a stim, now it doesn't. The car will run sometimes (usually only a few seconds) and then die as the RPMs drop until they reach zero. Since this problem makes the car undriveable I need to get it fixed asap. I am sure that it is the board itself as I plugged Jared's (ColdFusion21) board into my car and it ran great with no problems whatsoever. I now am sure the problem lies within the MS unit.

Here is a picture of my board that I took this evening and you could see if anything at all is out of place it would be great as that's what is wrong.

http://img228.imageshack.us/img228/1614/msboard7hl.th.jpg (http://img228.imageshack.us/my.php?image=msboard7hl.jpg)

Also if anyone, Kenny more specifically knows which circuits and resistors relate and operate the RPM signal, I would love to know which ones they are and how to diagnose this problem. I'm guessing it might be a burnt out compnent as it used to work.

Finally, I have a dyno session reserved for this Saturday for tuning and need the car running by then. If anyone locally (Portland area) has a MegaSquirt unit that they have lying around (yes, I know it happens...) that I might possibly be able to borrow and/or rent for about a week or less till I get this RPM signal fixed on mine it would be AMAZING and I would be incredibly greatful. As in I'll come over and help you with your car(s). :) This is for my DD and I am having trouble without transportation lately.

If anyone has any information at all, please just post. :)
Thanks, Nick

guywithFX
05-17-2006, 08:36 PM
OK, so I talked to Kenny today and later retouched every solder point on the entire board and that got me nowhere. So now I'm wondering what to do. When I plug it into the stim the Fuel Pump and Fast Idle Lights light up for about 1 second and then turn off. Nothing else on the stim happens. Only the sensor values are adjustable in MegaTune on the stim and the RPM and Pulse Width gauges are Red (Inactive). Please help, I know that something is fried by now, but I don't know what it is....

guywithFX
05-18-2006, 08:48 PM
finally, after a few days i have diagnosed and the cure has been found! turns out it was the optoisolator IC (6-pin IC near R10) that was bad, replaced it and now it runs like new.... thanks to kenny for his help, you're amazing :-D