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

Ok, heres what I have: 454 Chevy, port injection, 8 pin HEI dizzy, MSII 2.36 code, IAC stepper, heated narrow band O2.

The first time I fired it up it ran pretty good considering it need a lot of tuning. I got it to idle pretty good, set the trigger advance, then proceded to finish hooking up my exhaust system and O2 sensor. Well after completing my exhaust & O2, I fired it up. Now it wont run worth a damn! The nice, brand new HPC coated headers started to glow orange(now they are toasted), and poping, backfiring, and wont idle at all. So I think its timing, so I unhooked my 5V bypass to find NO difference. Next I pulled all my injectors and had them ultrasonic cleaned and flow tested-all were good. Also installed the transister Booster in the Opto circut.

Now, back to start it again--same S*%*!!
I did manage to get it to run around 1000-1600 RPM and make a datalog. So I am posting them looking for all possible help on this.

Chrisape,

You need to make sure you are not running lean, and your timing is not retarded.

So set the idle VEs using the 'minimum MAP' method described in the tuning section of the manual. Do NOT use EGO feedback to set the idle mixtures.

Then check the timing with a timing light, use the Trigger Wizard in Megatune to calibrate the trigger offset (as described in the manual), and then verify that your timing advances properly. If it doesn't, check your settings and your wiring.

Lance.

I checked my timing, it is correct with the trigger wizzard. I set the base timing with 5V bypass unhooked at 2 BTCD, then hooked up bypass and adjusted trigger offset so it reads the same in Megatune. I ended up with a +2.0 in trigger offset. The timing advance seems to be working ok. Where do the pops and backfires in the exhaust come from?? Is it from unburned fuel or timing? This is really weird because it was running ok. I am almost ready to find a carb and vacuum advance dizzy!!!!! I am using the same VE table that I started with(It ran with no backfires), so I dont think I need to move those values yet. It does smell really rich.

Chrisape,

Have you tuned your idle VEs - I would certainly try that.

Make sure you don't have the injector settings to 1 squirt/alternating, which will do just what you describe.

Check that there is no fuel leaking from the fuel pressure regualtor vacuum hose (a rupured diaphram will do this).

Do you have hi or low impedance injectors?

Did you wash the board in 99% isopropyl alcohol or acetone after you assembled it?

Have you checked the MegaSquirt on a stim to see if the injector drivers look good? Have you checked your wiring harness (it sounds like one of the injector leads that go to Megasquirt might be grounding).

Let us know what you find.

Lance.

Gonna check everything and post back! Thanks Lance!

Got it !! Bumped up my idle VE's, that calmed the backfiring down. Then I rechecked my timing and had to adjust it a few degees. Hope I can take it for a cruise tomorrow! Thank again Lance! Will post some pics when I am all Done!