MSefi.com read only forum (Jan.15,2018)

Im having a problem with my 8 pin hei on cold starts. When i first start it cold it drops the tach signal intermittently. Once it gets up to temp its like a totally different motor. Ill post a datalog and a tune when i get to internet i can get my laptop on.

Ms2 v2.890
V3.0 board
hei pullup mod
trigger falling edge
350 chevy 4.3l tbi unit correct tbi distributor

msq and datalog

I'd first try adjusting the sensor gap.

I dont have a way of adjusting the trigger gap cause its inside the distributor. It runs fine on ocassion when cold. Ill email you my datalog tonight.

I am very curious about this as I believe I am dealing with the same issue with my HEI 7 pin. It starts and runs ok under 2000 RPM. If you go over 2000 or make any quick movements of the throttle the signal drops out. But when it is warm is runs great. Haven't had a chance to log anything yet but will try tomorrow.

I'll start another thread if you want but I figured it would be OK since we seem to have similar setups and similar problems. Attached below is my MSQ and log file I took this morning.

It ran perfect on the first trip when it was 20deg. On the second trip it started acting up so I took another log. You can see right away the RPM spikes. And when this happens the TACH in the car drops to zero.

My car is an 85TA with a 305/5spd converted to TBI with MS2 V3 w/ 2.890 firmware.

Since its a similar problem Maybe we can try a few things and see what might help it. Im going to change my fast idle to control the 5v going to the distributor. They may help my slow start issue as well. Where is your ground points? Mine are both on my intake but on seperate locations.

Well initially I did not have the ignition module ground connected. I saw it had a ground screw right to the distributor so I didn't bother with it. So yesterday I tried connecting it to the ground on the intake where all my other grounds are and it made no difference. I thought today I may try running that ground over to the body but I don't think it will do much.

I'm starting to wonder if I have a bad or flaky ignition module since temperature seems to make a difference. It is original from 85 so it is a possibility.

My 5Vref is currently always connected to the TPS right at the throttle body. It makes no difference with the noise if I have that disconnected.

I recently added a stepper IAC but it did this before that as well.

I also thought it may be a bad solder joint inside the MS so I may open it up again and retouch all the joints I recently changed.

I am also running the HEI mod with the 100 ohm resistor wire.

Also you say you posted your datalog but I don't see it I only see the MSQ attached. I would like to see it to compare to mine.

Ill grab a shorter log today when i leave work and remember not to save the entire drive home from work. I still need to get my o2 sensor hooked up in the exhaust. Im gonna try new wires cap plugs and maybe a coil and see if it helps. Im running a new wells module from autozone. Im going to go scouting for another distibutor that is rust free on the inside.

Msd cap and rotor
taylor wires
Autolite plugs

datalog.

Well my car is useless at this point. Nearly left me stranded out test driving and now it won't even idle. I was able to limp it a little further to get it to my garage by disconnecting the 5Vref. I touched all my solder joints tonight and it made no difference. I am going to undo the HEI mod and see if I can fire it off the VR sensor like it was before I started messing with the distributor.

Well last update for tonight. I swapped over to the + side of the VR sensor (green wire) while still on the HALL/OPTI circuit with HEI mod removed. Now the car runs only in base time mode with 5Vref disconnected and there is no noise as the car revs up fine. As soon as I connect the the 5Vref the computer goes crazy and the idle is all over the place. Watching the injectors I can see the fuel stop flowing for a split second and come back.

So basically I am coming to the conclusion that either the ignition module is indeed bad or something is terribly wrong with my MS in the ignition circuits. I am leaning toward a bad module at this point because tapping off the VR sensor bypassed the module on the input side and the car runs fine. As soon as I enable to output I think the module is super noisy causing the MS to reset and act wierd. I will know more when I get the new module tomorrow.

I attached a short datalog of the car idling. It starts off with 5Vref connected and when it smooths out is when it is disconnected.

*EDIT* I noticed I mentioned disconnecting the 5Vref before to limp it back to the garage but it still caused resets and stalls. Moving over to the VR sensor removed the noise in base time 5Vref disconnected.

Im running mine through the module with this issue. Awaiting the cap and rotor through work. While im in mine tonight im swapping the fidle circuit over turn on 5 volts after its running and get that working right. i experimented with mine this morning and unhooking my 5vref it cranked easier than ever. It didnt change the signal drop out though.

Do you have another distributor you can drop in yours? I may swap mine if the issue persist and i just found my old 4.3 module last night and its a factory module so i might try it. Im leaving my hei mod installed cause drivability when warm hasnt changed. Im looking for a good coil to try as well. Might look into the transistor mod and see if that help any.

I was triggering off the module and that is what I changed last night. I got a new module today and will test it when I get off work.

Well I installed the new module and was unable to use the VR sensor anymore. So I put the HEI mod back in and fired the car up. I found that there was noise in base time and even more when the MS was controlling the time. It was different now as it spiked to around 7000 RPM instead of 4000. I was unable to go above 3500 RPM as it would spike. So I started playing with the Next pulse tolerance. I started off at 25% and started going down. I ended up at 5% and 90% of the noise went away. Still some stutters down low but I was able to rev out to 5000 RPM without issue. My situation seems to be worse than yours so maybe your problem can be solved by this setting.

So the car is driveable now and it is obvious I have a bad noise issue. I think I read somewhere increasing the R12 resistor can help with noise. Is that true?

On a side note I even tried removing the alternator belt thinking it could be making some noise and it made no difference. I also grounded the module to the car body with no difference.

I recall having the same issue when I started my project.

When cold, like zero, it would fire and run for only a second or two. Each time I restarted, it ran a little longer until the engine would be warmed up. When warm and driving, the RPM would drop out ittermitantly and cut fuel. Tried a new generic module and was worse off. The VR input circuit solved my problems. I have not had any ignition issues for the past two years.

Good luck!

Silverado wrote:I recall having the same issue when I started my project.

When cold, like zero, it would fire and run for only a second or two. Each time I restarted, it ran a little longer until the engine would be warmed up. When warm and driving, the RPM would drop out ittermitantly and cut fuel. Tried a new generic module and was worse off. The VR input circuit solved my problems. I have not had any ignition issues for the past two years.

Good luck!

Did you run the vr circuit off of the module or the 2 wires in the distributor? I didnt install my vr circuit like I should have but all the parts are in a bag i have set aside. Im gona play with some of the next pulse settings and see what happens. If it really dont get any better Ill find a new trigger wheel form my edis setup and sap it that way. It dont help though cause im wanting this in my other truck as well and ill be using the same setup. I have a small list of stuff im doing after work tomorrow to try.

Relocate the coil and distributor ground
Rewire my relays and reroute all my wires.
swap to a factory module
replace the ditributor
Add a 5 volt relay to control the vref.
Ill mess with the next pulse before first start.

LilSki wrote:. So I started playing with the Next pulse tolerance. I started off at 25% and started going down. I ended up at 5% and 90% of the noise went away. Still some stutters down low but I was able to rev out to 5000 RPM without issue.

I did experiment with that some this morning. It helped a ton. Im still gonna try a few other things as well. I also ran 65 on my tach mask.

Glad to see some progress on your end! If I don't figure out mine I may experiment with my VR circuit on the VR sensor. I couldn't get it to work on the 4 pin HEI I tried before but it may work with this 7pin setup.

Current settings on mine
Tach mask % 60

Next pulse tolerance
Cranking 50%
Afterstart 30%
normal 15%

I need to fine tune the cranking some and get my iac to close and work right. Im gonna datalog my start when i go to lunch and see if i can fix it in tunerstudio. If I get it right Im gonna just do some basics tonight and get it to crank on first bump of the key.