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Forum nameEngine Management Systems & Controllers
Topic subjectcrazy afr/map/tach spikes
Topic URLhttps://forums.2gnt.com/dcboard.php?az=show_topic&forum=i54&topic_id=2653
2653, crazy afr/map/tach spikes
Posted by CarbonFiberRST, Oct-12-06 01:27 PM
Ok I have a datalog that I can email anyone willing to help. Just either pm me or post your email.
I'm veiwing it with MegaLogViewer.

at 1395.722 seconds the rpm is pretty steady except where it goes from reading 35 to reading 36 but the AFR and MAP go absolutely NUTS.


at 1425.783 seconds you can see that the tach spikes downward and the afr and map get a little jumpy (compared to the first instance mentioned)


While driving everythings cool untill around 3500rpm-4000rpm my greddy profec b doesn't pic up the map flucuations but I can look at the gauge on my laptop and its bouncing back and forth also the zeitronix wide band shows the afr going from 10:1-21:1 and I can slightly feel the power loss and gain of the car while cruising. I think this log was all done in 5th gear on the interstate. as you can see I don't boost any. If i try to boost from that rpm range the car jerks pretty bad and If i stay in it, once it passes 4k it will accelerate normally. If I floor it from say 2000rpm it will sometimes slightly stutter at those rpms and sometimes it will buck bad. Anyways lmk if you know what It might be? this is my first time actually viewing a log in graph form. Also, this problem just started 2 weeks ago out of the blue and didn't go away when I loaded a really old .msq (pre-problem) so something happened... Also disregard all spark info, its not hooked up. lmk if you need any other information

EDIT: since pretty much evertying is spiking is it most likely poor gounding? Its never been an issue till recently though...
2660, RE: crazy afr/map/tach spikes
Posted by CarbonFiberRST, Oct-15-06 04:58 PM
i ran two 14 gauge grounds to the batt and a 14 gauge power to the batt... nothing changed.
2662, RE: crazy afr/map/tach spikes
Posted by Chamuko, Oct-15-06 05:41 PM
what board ver are you on?

Also, like you mentioned, all your sensors associated with the MS are a bit weird to me...then again I have yet to start tunning mine...

Anything come loose?
2663, RE: crazy afr/map/tach spikes
Posted by CarbonFiberRST, Oct-15-06 06:45 PM
v2.2, nothing has come loose that I know of... I'm going to pull the seat out tomorrow after work and check all the wires and look at all the shit I soldered to see if there are any cracks in it or what have you...
2664, RE: crazy afr/map/tach spikes
Posted by dougie2, Oct-16-06 09:32 AM
What's up with your CLT signal?
2665, RE: crazy afr/map/tach spikes
Posted by CarbonFiberRST, Oct-16-06 11:57 AM
the same thing thats wrong with all the other sensors. thats why I'm here asking. Those are just 2 screen shots showing the problem, usually its a straight line at about 203 degrees or so...

Is a 14gauge wire large enough for the constant 12v power source?

The jerking while accelerating through that rpm range in the lower gears (1-3) is actually alot better since running the wires, it only jerks once instead of constant but while crusing it still does just like you see in those screen shots.

But again, nothing was wrong just 2-3 weeks ago... and the issue is isolated to 3,500-4,000 rpm

I only changed 1 thing about a week before this problem occured and that was I installed a vacuum manifold to clean up the 5 things I had T'd off the stock 3 prong vac source on the manifold. I used a pretty large hose from the intake manifold (3/8" I think) thats about a foot long and it goes into the alluminum block that has the 4 vac hoses going to it, and the 5th hose I put where the pcv valve was attached to the manifold and I routed the part on the valve cover to a catch can along with the other valve cover vent... before I ms'd I didn't run a pcv valve for about a year or more and never was an issue. Could any of this cause it? again about a week after I did these small mods the problem appeared... I'm lost.

This is from before the issue started. I didn't change anything to do with wiring, only whats stated in the above paragraph.
2668, RE: crazy afr/map/tach spikes
Posted by CarbonFiberRST, Oct-17-06 06:40 PM
Please help, I'm too stupid to figure it out on my own.
2703, RE: crazy afr/map/tach spikes
Posted by CarbonFiberRST, Oct-27-06 04:47 PM
thanks :squint