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

I am having a issue with some spikes a erratic rpm again. I had this issue last spring, rewired, changed all the grounds, new sensors and it mysterious quite. No idea what the problem finally was. Ran good all summer. It is a 350 chevy running MS2 fuel only using a flying magnet to trigger. Got it out of storage this spring and it is acting up again. I have attached the last datalogs. The CLT is very erratic also and the temp jumps a few degrees at the same time the rpm jumps. On one datalog, I unhooked the clt and it really spiked. I checked all the grounds again. Any ideas?

Also noticed the voltage varies quite a bit during the same erratic issue. I have the ecu in the trunk and combined all the grounds in to 2 14 gauge grounds directly to the battery. Is this enough grounds?

More ground wires wouldn't hurt, but those should be adequate. You may also want to adjust the VR trim pots a bit.

Any suggestions on which trim pot and which direction or is this a trial and error thing? I am relatively new to this and bought my unit rather than assembling it myself. It was just upgraded to add ignition control with a single coil. It originally was built without the ignition control section finished. I have not controlling ignition yet as I am making sure everything works before I jump in. Would this have anything to do with it?

It is a bit of trial and error, but we have some tips here:

http://www.DIYAutoTune.com/tech_article ... _index.htm

Switched the sensor grounds to the ecu and the ecu grounds to the battery. Runs good no spikes. CLT is calm as can be. I used to have to run the crank trigger .18 out to get to run and not spike all the time. Had to move the sensor in to about .06 to get it to signal. Such a big improvement now my tune is off. Too rich. Have been able to lean out idle about 10 spots in the VE. Hope this fixes it for good. Thanks for the help

You're welcome, glad to hear it's running better now.

Keith, This wouldn’t happen to be a corvette would it? Sometimes they have a horrible ground between the 3 biggies. Battery & Frame & Engine (fiberglass body). Your coolant and engine spikes screamed of a poor grounding issue. The “engine” spikes in MegaLogViewer at 152 said lots of sensors were freaking out.

I like your grounding the sensors to the ECU. That’s great. And the ECU to the battery.
I saw your spikes looked very similar to mine.

I had my grounds all tied to one bolt on the intake manifold for ground, a single point ground. But the ECU got it’s voltage from the battery (and it’s Ground from the engine). That was not a good idea.

I have problems with my ignition circuit with an 8 pin HEI. I hope to get that figured out.
Thanks, I’ll use your method of grounding on my car starting tomorrow.
For Accel Enrichment, usually you only need it from idle up to 2500-3000 max.
When you changed the ground I hope it fixed your dwell spikes too.

For your rich conditions, I use MegaLogViewer and have the AFR table set to what I want. Then with MegaLogViewer, activate the VE Analyser and within about 3 or 4 datalogging times the VE is pretty well dialed in.
I set the idling area for about 14.2, and the rest a little lean. But I have a tugboat cam, as the car is real heavy and it is used for cruising not racing at all. My 454-502 is real happy at 16 or so to 1 while cruising.
Don’t use my ve numbers as my injectors are different than yours and my cam, but they should give you a picture of a reasonable VE and AFR and such to lean it out. Remember I have a tugboat cam. 4500-4800 and it’s all done!

Holl