VR ignition drop out - occasional

[Don]

I've built a new MS-II ECU with V2.886 and jumpered the Hall setup. Had lots of Ign. drop-out issues, tried #2 Mod fix, then swapped out many resistors in R12 with no hope for a cure as the problem persisted. Tried 220 ohms all the way up to 1.3K ohms.

Then I undid all the hall mod changes and went to the VR jumper set up with better results, but I still get an occasional Ign. drop out. I've had them at Idle and at higher RPM's.

I use a small cap HEI where the dwell should be 2.5ms for my 8 pin, but it likes 3.5, like the 7 pin large cap HEI's. I have changed out the distributor for a MSD Billet plug-n-play - not sure if this is what changed the dwell needs.

Anyone have an idea why the drop out ?

I am much better off than before, but would like to get this little annoyance resolved as it might affect passing emissions in 2 months.

Thanks

Don

[nismoryco]

Have you tried adjusting the R52 & R56 pots? This might help.

This is from the manual:
Start with the R56 pot all the way counter-clockwise, and R52 about 6 to 8 turns clockwise from the fully counter clockwise position. The fully counter clockwise position is reached when the pot clicks (you can feel and might be able to hear this). The pots are 25 turns from the fully clockwise position to fully counter-clockwise position.

[Don]

Hello nismoryco,

Yes I have messed with these pots quite a bit. I have them where I feel I get the least amount if ignition drop outs. There are just some random drop outs that I wanted to get rid of. The Hall fix was to change the value in a resistor, just like what I am doing with these pots. Is there another resistor or component in this circuit that may also need swapped out possibly due to tolerance stack up, etc ?

Watching Megatune confirms it is a drop out as well as my digital LED bar tach (OEM).

I wouldn't be so concerned about this random miss, but am sure it will affect emissions. It will miss on average once per 1-1/2 to 2 minutes.

Other info: The coil is new - MSD Blaster external coil - direct stock replacement. Distributor module is new from MSD - Came with Dist.

Thanks
Don

[nismoryco]

Sorry, I am not real experienced with VR sensors yet. What about the air gap between the sensor and the trigger? Also, I've heard about some people adding a resistor in series with the VR signal. I'm not sure what this actually does.

[Don]

I'll search for that in the forums and try it if I can find it.

I want to also swap out the HEI Module, putting a stock one in as the distributor came with a "High performance" module which I have no clue what they did to make it that way, so I'll start with stock and once this miss is gone, I may work my way to their module. I have a feeling MS-II can give me all the performance I ever wanted.

Thanks for the reply and info nismoryco

Don

[Don]

I bought the 2N2222 "grab bag" transistor pack from Radio shack and it does not have any 2N2222's in it. (I bought 2 packs - all they and the surrounding stores had) What it does have in it is a "MPS 2222A". Will the MPS 2222A work ? I looked the specs up in Digikey and they are similiar but under "other names" does not list/cross reference each other.

My other choices in the packs are : 2N4401 O11, 812 PN 3643, G12 MPS 5179, 912 MPS A05 and 818 PN 3645.

I can order the 2N2222 from Digikey, but do not want to wait if I have something that will work.

Any ideas ?

Thanks

[nismoryco]

Are you trying the transistor mod for the hall circuit? If so, the MPS 2222A should be fine for this.

[Don]

nismoryco,

Yes I am trying the transistor mod as a last ditch effort to cure the ignition misses.

I'll try the MPS2222 and let you know.

Didn't want to waste a weekend an not work on this issue.

thanks