Random lean a/f during cruise

4g63tcrazy · 01-17-2009

So I installed an AEM UEGO wideband on my daily. Basically just so I could tune it for gas mileage using the SAFC. So on my way home, I'm cruising at about 70mph, the a/f was bouncing between 14.7 and 15.0 with the SAFC at 0%. But I want to save a little gas so I usually have the SAFC set to -4%.

Now as I'm cruising, I start going up a hill so I start approaching 1psi. Then I feel the smallest little studder.. Like if you werent paying attention you probably wouldn't feel it. But I always pay attention to my car as I'm driving. Anyway, every time this tiny studder happened my a/f would go as lean as 17.0 to 20.0! So I would get back into vacuum while cruising and the a/f would just stay that lean.. So I would go into the settings on the SAFC and richen up the mixture til the a/f was in the right spot again. (14.7, 15.0)
Once it get's back into that right spot I tried leaning it out with -4% fuel again. Then the a/f would be right around 15.2 to 15.4 and it would stay like this until I got to about 1psi.. Then I'd feel the tiny studder, look down and the a/f went lean again. Then richen it back up ect..

So I kept playing with it and if I have the SAFC at -2% it will not lean out once I hit 1psi like it did before but the a/f would still be around 14.7 to 15.0 like if it was at 0%.

The only thing I could think of would be the fuel pressure regular not upping the pressure per 1 psi and then the car leans out.. But my car will stay leaned out until I richen it up about +6 percent!

So what do you guys think? I can't think of anything else other than the fuel pressure regulator or maybe the ecu is not liking me taking out fuel.

brando · 01-17-2009

th ecu could just be very mad at you. dsm's are hungry bishes. i would try getting a 2g fpr if your going to do this. you might not be sending enough fuel thru so it might not want to open correctly. you also might have a bad connection on an injector or the rectifyer might be going bad

4g63tcrazy · 01-17-2009

I'll make sure all the connections on the injectors are tight. Then I'll probably put on my stock regulator off my red car. I know that one works for sure. What is so much better about the 2g regulators?

niterydr · 01-17-2009

What are your throttle points? What FPR? Pump? Injectors? How do your plugs look? What fuel?

4g63tcrazy · 01-17-2009

I put my throttle points at low-55 and high-60. I usually put them at 30-80 but with the auto I'm always giving it about 50% throttle to accelerate. The fpr is the 5 speed one to go with the 450cc injectors and the 5 speed ecu. Haven't looked at the plugs and I'm running 92-93 octaine gas. I am also getting 23mpg highway. Which I think is a bit low..

4g63tcrazy · 01-17-2009

Also the highest % of throttle when going up hill on the highway is 31% and the lowest is 17%. I do not range out of those percentages while driving on the freeway.

niterydr · 01-17-2009

I would try seperating the low and high throttles, the S-AFC grabs the low setting for everything under and the high setting for everything over, it "fuzzies" between the throttle points.

I am assuming the converter and drivetrain isn't slipping?

4g63tcrazy · 01-18-2009

No the converter or drivetrain is not slipping. When I get that little studder I can tell that I have lost some fuel and just a little loss in power.. I will try putting on the other regulator and I changed my throttle points back to 30-80.