Mark_L

iTrader: (2)

So I'm having a lean idle issue after swapping out a failed fuel pump.

Here is a little background: The car is an Evo IX, FPRed powered, stock block, on E85 around 500WHP with a direct wired fuel pump. I had a DW300 fuel pump go bad and replaced it with the same model.

Now my car idles very lean and the STFT is 24+%. As soon as the engine load increases around 30 the tune is right on. I don't have a fuel pressure gauge or measurement of the FP, so I don't know if the rail pressure increased or decreased at idle with the pump change. I know from the past on my other evo the higher pressure at idle with low duty cycles have caused the injectors to not want to open causing a lean condition. I played around with the fuel map down low and it is not changing the STFT very much.

Is there another way to tune for this condition? Besides the base fuel map that seams to not want to work very well.

Toekneee!

iTrader: (3)

Are you full time open loop? If not, changing fuel map down low would do nothing from my understanding. You could go full time OL and adjust fuel accordingly but some people don't like that.

Log fuel trims and scale injectors. Something may be off.

Mark_L

iTrader: (2)

Thanks for the response. My mistake that the fuel map changes only effect open loop fuel increments. It's been awhile since I tuned using ECU Flash, it’s like riding a bike. I have been playing around more in AEM tuner and pro the last couple of years!

I adjusted the Batt Volts on the injector table to compensate. All is good now! It's just weird that this happened by swapping a pump, with the same model.