nightster

Well my problems started a while back. I popped a belt then I got the lean codes p0171 p0174 about two weeks after. Looked for a vacuum leak and couldn't find any thing. Shortly there after my fuel pump burned up (I suspected I had ran the fuel level low and the BAP over heated the pump). With a failing fuel pump my pressure would drop causing a lean condition and throwing the codes or at least I would think. After 7 months I finally had the time and funds to put a new pump in the car. Everything ran great for about 2 weeks then the two lean codes got thrown again. I ordered a new MAF and again checked for vacuum leaks. Replaced the MAF and no vacuum leaks found so I deleted the codes and tried driving it again. Then a day later the pump I had just installed failed on me. So this time I assumed it was the BAP burning the fuel pump up. I removed the entire BAP system racetronix harness and all in favor for an ECS stage 1 fuel system. Got the new pump in, got the fuel system all hooked up. Then yesterday while driving I got the same two codes and I started monitoring my fuel trims. Only at start up, hot or cold idling, they jump to +24.2. Then once I start driving again they drop to between +2 and -2. If I stop, they jump up again. If I sit for a while they will drop slowly to about +16ish. What I'm thinking is maybe I had hooked my BAP up wrong and the BAP had my fuel pressure higher than normal all the time and once I removed it for the fuel system my fuel pressure is lower now causing it to lean out at idle. I noticed my car idles a lil lower and rougher and there is a slight hesitation when lightly applying the throttle, both of those were nonexistent before the fuel system. Would lower fuel pressure make my fuel trims go lean? I will be putting a wideband on the car this week, also any tips on monitoring my fuel pressure would be appreciated. Contemplating on taking it to a local shop and putting it on a smoke machine to make sure I don't have any vacuum leaks. Sorry for the novel, just trying to be thorough.

schpenxel

Lower fuel pressure would make them go lean but I'd expect it everywhere if pressure was lower everywhere

Probably needs some MAF/VE adjustments

nightster

VE? I'm at a loss right now as to what's wrong with the car. Talked to my tuner about sending him a log to see if he can correct the lean issues at idle but IDK if its a tune thing or if there is something I have done wrong. When the car is rolling down the road it runs great, just the trims go lean when the car is stopped.

schpenxel

I'd try adjusting MAF/VE (SD) tables first and see if it stays consistently closer to zero after being tweaked.

The short version is SD mode uses a table called a volumetric efficiency table. It basically says what % the cylinders are expected to fill at different RPM/MAP combinations. So if a cylinder was 1 liter (for sake of easy math) and on the intake stroke it brings in 0.7 liters of air the volumetric efficiency there would be 70%. There's a few hundred cells in the VE table(s) (and oftentimes there's one for out of boost and another for boost)

nightster

Got it, I found a local shop with a smoke machine. Gonna call them tomorrow and see about having the car smoked to ensure there are no vacuum leaks. I feel if there were though the way the car drives would be effected not just at idle. Right?

schpenxel

I'd say probably but not necessarily. Airflow is lowest and vacuum pretty high at idle so leaks would do more then. But a smoke machine will tell you real quick if that's an issue or not, then it's not a guy on the internet guessing

Mike's LS3

"What I'm thinking is maybe I had hooked my BAP up wrong and the BAP had my fuel pressure higher than normal all the time and once I removed it for the fuel system my fuel pressure is lower now causing it to lean out at idle."

From my experience, if the BAP was hooked up wrong the car would not start (hot wires reversed). Also, with the BAP hooked up correctly, the hot wire should read 13-14 volts at idle. If you put a jumper wire on the hoobs switch, the hot wire should read around 17 volts. BAP kicks in at around 3 psi, not at idle. If your fuel pump voltage is around 17 volts at idle, you could have a bad hoobs switch.

schpenxel

Some of the boost a pump are setup so that if the trigger wire isn't connected to ground the unit is "on", kind of as a safety in case the wire comes loose. Something like that would probably be enough to increase fuel pressure at idle

I don't think that'd be responsible for 25% fuel trims but who knows (assuming they were close to zero to start with.. which is a bit of an assumption)

nightster

Got my wideband installed. Car idles between 13-15 afr and cruises between 13 and 14.5. Idk WOT bc my wideband won't read that low. It's below 10...

schpenxel

Are you running meth?

You should be bouncing around +/- 14.7 at idle/cruise but it's probably fine

Below 10 is pretty dang low though...

nightster

No meth. Yea pretty rich