So recently I replaced the fuel pressure regulator, fuel filter and added 380cc injectors. My first set of 380s were bad and I was constantly running rough at idle and leaning out, not all the time but too often. Switched out with new 380s. Ever since then in the morning my afr gauge shows that I'm leaning out (idles and drives fine) for a couple mins of driving then fine the rest of the day, it's usually fine after 8 hours of work too. Leaning out at idle and well normal driving that is, never at WOT or more than half throttle. I need to replace my pcv valve and gas cap (doesn't feel like it seals well at all), that will be done today. If neither of those help.. Then all I can think is fuel pump is going, wideband afr gauge is going, or maybe my o2 sensor. I don't know though, any opinions would be great.

My car is a 02 r53 with almost 150k miles. Compression was good a month ago, spark plugs look good and are new as well with wires/coil, catless exhaust, has a WMW quick tune but for stock injectors not 380s. My WOT afrs are 10.6-11.2 at 7k rpm or so, idle sits at 14.7-15 when I'm not having my leaning out concerns.

 

well 14.7 is chemically ideal, perfect balance in stoichiometry. and your in open loop so this is a number calculated from your 02 sensors and the ECU will do everything it can to get this number.

when at WOT, the ecu cannot calculate fast enough to keep the fuel trims ideal, so it goes to a set value programmed in the ecu, thats why your are so rich at WOT, you have bigger injectors than what your ecu is normally programmed to. and its always better to be rich than lean.

max power is created at 12.5-12.7

so it sounds normal to me, if you got the JCW tune, i bet your WOT a/fs would come closer to 12.5

 

I get that and my afrs are fine to me normally. I know I'm running overly rich and my normal afrs are fine. But in the morning it leans out after first darting it up. I'm talking 15-16 for the first few minutes of driving then it goes back to normal for the rest of the day including after sitting at work for 8+ hours. It's just in the morning after initial start up. The car feels like it idles just fine and drives just fine, but my afr gauge is showing it run lean in the morning for the first couple minutes of driving. It's odd.

 

i wonder if thats on purpose, my afr gauge isnt in so i cannot back you up, but maybee its running lean to help msooth out idle, increase temperature in the block to help get things to temp including the 02 sensors?

 

That's an interesting thought. I never considered that possibility. Could be doing that considering the WMW quicktune I currently have was set for stock injectors. It never did it prior to the new injectors and replacement fuel parts. I plan to get a cam and tune done by end of summer, so getting an adjusted tune wasn't on my agenda. I was doing all my fuel replacements and figured I'd do the injectors while I was there lol.