legacycentral bbs

And it seems to have taken off.

So when I installed the 370cc injectors in place of the stock 270cc injectors, I of course was running WAY rich and my milage dropped to down about 12 mpg from the low twenties. I installed a poteniometer in the MAF signal line and so now had a crude AFC by which I was able to "tune" my car and get milage almost up to 18 mpg while cruising and puttering around town.

Until yesterday. Suddenly the car jerked, bucked, hesitated and make general back engine vibes. Unless I turned the poteniometer up. Then it would run fine.

So what it seems to have done (no proof of course) is that it has figured out it has bigger injectors and when I turn the MAF signal down, it is injecting the proper amount of fuel for the signal, but since the MAF signal has been modified, it is wrong and the engine isnt getting enough gas.

When I first installed the poteniometer, you could cruise along and turn the knob back and forth while keeping a steady rpm and "just" feel where the the magic spot was. Now if you are cruising along and turn the knob back and forth, the magic spot is like switching the fuel off. OK, not that bad but really really noticable.

On boost, there is no problems and I still have to have the poteniometer turned down a little or it gets too much fuel over 6000 rpm.

So whether this is bad bad, versus bad annoying time will tell.

Yeah that's how it's supposed to react. You could always reset your ECU until it relearns around the fuel trims, then reset it again, and again, and again... Personally though I'd start saving for some engine management.

I just don't buy that it will learn around a AFC. If you reset the ECU and don't run it without the fuel trimed how you want it there is no way for it to learn anything. It uses the AF meter and should trim it to run well with the altered MAF signal.

Ehh... or you could see if you could make a switch that will instantly reset the ecu for you... that'd be cool. That way you can run what you need enrichment-wise and with maf altering off of a base map. Instead of one the ecu tries to correct.

Car starts acting up or acting funny... Flip o' the switch and BLAM base map again.

If you remove fuse 16 the ECU won't have any power for its memory backup but will still function correctly when the ignition is on.

If you want to prevent the ECU from learning fuel trims, though, couldn't you just disconnect it from the oxygen sensor?

Well I tried resetting the ECU but it still has the shakes under normal driving. Under boost everything seems fine, but while normal, the car hesitates and jerks....sometimes....sometimes it doesnt.

I think I need to change the sparkplugs though just because you never know. Only changing the plugs is a bitch now because of the SC. Ah, the futility of power.

OK, I did reset it this time and it is back to driving normal but rich. I hope.