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Old 11-08-2008, 07:04 PM   #1
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Default Voltage Spikes In Datalogs? (help!)

Alright, I've been fighting this since I built my standalone MS2 setup. I have voltage problems that show up in datalogs. They show up as both spikes up to ~22V and dips down to ~8V. I also have fought the problem of "noise" in the signal lines forever (coolant reading, MAP, TPS, AIT, all of them except AFR), and have thought there my be a correlation. Sometimes the engine will randomly just "go off" for like .2 seconds. Sounds like I bumped the key off and then right back on. Never get a reset with MS, never loose sync, etc. I can even datalog the events. Anyways, there's a correlation between "off for .2 seconds" and "voltage drops to 8V for .2 seconds". According to datalogs, they happen at the same time.

Here's some screen shots from datalogs. I could take 100 shots where this happens. Happens like every 2 minutes or so. You'll note that in some of the datalogs the RPM drops immediately following the voltage drop. That's the engine going off for .2 seconds. Some datalogs are me driving, so the engine goes off, but since the car's in gear and moving it doesn't show up well.

I think I FINALLY got rid of all the sensor noise! You'll note that in all but one screen shot that all the other sensors have noise messing with the readings. In particular, the coolant sensor is very suceptable to this. I have suspected my low ohm MSD sparkplug wires I made when I went standalone were the culprit. Well, today I "jammed" the stock sparkplug wires on the EDIS coil pack and what do you know? Noise GONE! Very very happy. Gonna have to find a way to better secure them now. But, I still get the voltage drops that correlate to the engine going off... Any ideas are welcomed.

Also I didn't post any pics of the voltage spikes that show up. They don't seem to cause the engine to go off, though they do cause acceleration enrichment to come on and cause the engine to bog for .2 seconds. Furthermore, they "might" have been from the low ohm wires as I used to get a "high" spike every 2 minutes. Made a 20 minute datalog after using the stock wires and so far, no more high spikes. Only the "dips".

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And this one is after using the stock sparkplug wires. No more noise!
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Old 11-08-2008, 10:03 PM   #2
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And after a trip to the store, it drives 20 times smoother. Wow. No more stumble off idle like it did before, and it's just overall a lot smoother. I cruised at 5K in second and it just sings like never before. But still I'd like to fix this "off for .2 seconds" problem. Joe Perez, any ideas? I PM'd you about this a week ago but never got a reply back. :(
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Old 11-09-2008, 06:31 PM   #3
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Thanks for all the suggestions guys.....

Did some testing on the car to no avail. Tried running +12V directly to the MS2 in case it was loosing voltage somehow, but it didn't make a difference. Tried swapping relays, nothing. Tried moving grounds around, nothing.

Anyways, after a couple hours of searching and reading on MSEFI, I have read that some people running MS2 with low ohm injectors have problems with their flyback circuit not working properly. Lots of people posting that they have "voltage spikes" in their datalogs and the map signal is noisy, and that when the map swings it triggers acceleration enrichments, causing the engine to bog and die, but then it comes right back on like normal. Sounds EXACTLY like my problem.

The solutions vary a lot, but the accepted "best fix" is to provided a separate return for the flyback circuit so that it will not interfere with MS. I believe every person that had this problem and did this mod reported it fixed the problem 100%. They say to unsolder the middle pins of Q9 and Q12 and solder a wire to it and run this out of the MS and directly to the fuel injector +12V source, completing the "loop" for the flyback circuit. So this is what I'm going to do. Just ordered 20 TIP125's so that I can do this mod and not worry about damaging one and not being able to drive my car. Will report back when it's done with results.
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Old 11-09-2008, 06:41 PM   #4
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Good luck with it pat, this issue is new to be, hope it works out for you.
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Old 11-15-2008, 05:25 PM   #5
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So I did the mod today. Had to remove the original TIP125's and install two new ones, not soldering the middle pin to the board. I then ran a wire off each of the middle pins and hooked them to the +12V wire that feeds the fuel injectors.

This made a nice improvement. Didn't fix the problem 100% though. ~1hr worth of datalogs and I still had a few voltage dips, but they were all less severe. Most of them went unnoticed when driving. So this is a step in the right direction for sure. The people that suggest this mod also suggest using a noise filter before the MS to completely isolate it from the noise caused by the injectors. So this will be my next step. However, nobody in this town seems to sell a 12V noise filter. Looks like I'll have to order one online.
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Old 01-04-2010, 06:28 PM   #6
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Hi!!

I was told or pointed out that I have voltage spikes showing up in my logs. Something like 0 to 22V.

I have no clue what it could be but I'm fishing for answers.

The car has a Coil on Plug set up that includes a bank of capacitors so I'm wondering if that may be the cause or a bad ground or a bad alternator ( ? )
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Old 01-04-2010, 06:41 PM   #7
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Points for searching, but I don't think that Pat will be along to help you any time soon. He's banzored.
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Old 01-04-2010, 07:04 PM   #8
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Old 01-04-2010, 08:50 PM   #9
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y is that funny??
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Old 01-04-2010, 09:13 PM   #10
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Quote:
Originally Posted by p51hellfire View Post
y is that funny??
Your avatar.... I love the cat trying to lick his own ***** ( ? )
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Old 01-04-2010, 09:15 PM   #11
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u on crack I have no avatar......
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Old 01-04-2010, 09:20 PM   #12
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Its actually a cat thats jacking off.
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Old 01-04-2010, 09:20 PM   #13
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Sorry I was looking at Steins white cat thingy
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Old 01-05-2010, 05:54 PM   #14
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Went to 2 Autozone stores. One told me I have a bad battery and one told I have a bad alternator.
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Old 11-22-2010, 10:31 PM   #15
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Right... probably both... might as well replace the starter while you're at it... and the flywheel so the starter can turn it over easily.... better rebuild the motor, new bearings will promote easy starting and smooth voltage!

Well in truth I'm searching for answers myself... lot of voltage noise in my logs, but no spikes... just steady bouncing from 14 -13.4~ probably just bad grounds but I fear either my battery or alternator are going because a few months back I noticed slightly less noise and more voltage... 14.4-13.8~... so I dunno. I'll start with fixing more grounds(like I haven't already fixed alot of them).

Probably going to scrape up the cash for alt and batt at the same time and do them both and see where we stand with new alternator, battery and fresh grounds.

Anyone care to donate to my chirstmas charging system fund?

Best of luck to those still having problems.
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Old 11-22-2010, 10:39 PM   #16
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Cleaning and fixing grounds is much cheaper.
Followed by alternator- Likely worn brushes.
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