6,281 rpms the car loses input from the motor rpm the will come back

[myblack98gst]

I did not even know this was happening till installed a DIS-2 after messing with that for a week I ended up taking it off assuming it was bad. after removal I did a log on the car and this is what it came up with.

rpm --- injp --- injd -- mafs
5625 - 10.49 - 49.2 -- 1163.6
6000 - 11.51 - 57.0 -- 1390.0
6281 - 11.77 - 61.7 -- 1478.1
-------- 9.98 -- -------- 1534.7
7812 - 10.75 - 69.5 -- 1603.9
7968 - 9.72 --- 64.0 -- 1503.3 <---end of pull let off gas car will go to 8,500 no problem


WHERE did the info go!!! I have several logs that cut off right at 6281 on the dot. BUT I cannot feel a studder or miss while making a pull at all it goes right past this with no problem. IF the MSD is on it however I get the same results at exactly 6281 BUT the LED light on the MSD goes off and the car starts to buck and wont pull past it.

what I have done.

replaced:

CAS
Coils (now running a evo ignition (same problem before))
wires of course


tested
all wires for CAS all show good for impedance and voltage
inspected harness for apparent problems cannot find anything
hook a VOM to the MPI relay on he 12volt outputs it holds voltage even when the signal is messed up.



I am just about lost at this point I do not know where to go on. does anyone have any insight as to what this could be or have had a similiar issue?!? WTF

 

[turboglenn]

Start shielding wires and running newer better grounds to start with. I was having similar problems on the motor chutting down at 7200 RPM but the still haven't solved it. I just pulled 7600 RPM out for the first time in months...

Start chekcing all the connections from iginition components

EDIT: what CAS are you running?

 

[myblack98gst]

original 1990 style taken from a low mileage car in a junkyard it and my original both have the same result.

this kind of stuff is what makes me wish I could just afford a EMS and be done with this 18y.o. wiring b.s.

 

[JayRolla]

My friend just had this issue but way worse, turned out to be the transistor plug was not connected completely and needs the clip to hold it on. He used a paperclip to fix his, the 91's and up didnt have that style of plug.

 

[myblack98gst]

mine had the same problem but I rigged some stuff up to hold it together nothing a few McGyver placed zip ties can't fix. haha

 

[turboglenn]

It definitely seems like a signal shutdown of some sort. No having a CAS signal for RPM i could see the ECU either going way rich or way lean (and yours's drops pulsewidth at that point). Is it a green top or a black top CAS? I've heard the green tops are more prone to interference by some and told less prone by others (mainly based on theory of signal types) but theory only seems to hold true about 75% of the time in real life :/

 

[myblack98gst]

it is a green top.. I have been out there staring at this thing for awhile and the ONLY other thing I found was the brass capacitor box for the ignition was not grounded it was just hanging there but it was connected. I went ahead and mounted it back down solid to metal, but it should have been working still.