mylittlepony1

I adjusted my stock VAFM Cog to 3 clicks lean because its been running very rich, especially since now I have a pretty much straight pipe exhaust. My question is will it eventually revert back to stock after the ECU reads that its running leaner? I've read multiple threads and none show a straight answer.


Not to be rude, but I don't want to hear about your opinion about adjusting the cog, I just want this question answered.

Punchy

The ECU will always try to run stoich and throw codes when it cannot.
But,, If the O2 sensor is reading incorrectly then the ECU is miss lead, Suggest start there if you haven't installed a new one already.
Then EGR.

Gamefreakgc

Running rich as it CEL? Or just running a little rich? Most of these trucks do, you can lean them out a little bit without any serious effects.


You can see what the computer is adjusting to by jumping E1 and VF1 (I think?) with a multimeter. Basically, you're looing for a value between 0 and 5 volts. 2.5 means no adjustment, higher is running lean so adding fuel, lower is running rich so adding less fuel.

mylittlepony1

Its just a little rich I guess, but it hasn't set off the CEL. Since adjusting the MAF, it definitely helped a little, I just don't want to have to keep pulling the EFI fuse to reset it all the time. I am eventually going to do the 7mge VAFM swap, and I know that will help a lot

Gamefreakgc

I forgot to mention E1 and VF1 are on the diagnostic port on the engine bay fuse box. It's the closest thing to tuning you can do without an air/fuel gauge and wideband O2 sensor.

Yeah if you're running a straight pipe-exhaust and want to get the most out of a 3.0L (which isn't much) the major constrictions are the VAFM, air cleaner hosing (a little too small and all those curves and chambers don't help), headers, exhaust piping size, then muffler.

A side note though, some have reported reduced performance with no back pressure in the exhaust which the catalytic converter would normally provide. I'm no expert on exhaust systems and will never try this since it's not smog legal in California but you might want to look into it.