Kretzmech

iTrader: (1)

So upon start up after about a minute at idle my car goes lean off the wideband scale. It will then begin to bogg I'm assuming because its going lean. While car is running my fuel pressure is steady at 3 bar, but once I shut her off the pressure drops quite quickly.
The research I found points to either leaky injectors or fuel running past the regulator back to the tank which may indicate a bad fuel pump.. but I never have a hard time starting the car it always starts right up.
So my symptoms are lean idle, and rapid fuel pressure loss after shut off and a code reader showing ECU pulling fuel while at idle.
Could this be a leaky injector(s) and the ECU pulling so much fuel that it causes a lean wideband reading?

vipervadim

iTrader: (10)

UUggggh.... I typed a fuel system novel for you, and then it didn't post.... and gone into the www ether...

here's the re-typed cliffnotes: Do 1-11 to figure out where your problem may lie.




1. Clean the MAF! and ensure your front (primary) O2 sensors are not failing (failing O2 sensors will make your car run worse/inconsistent. can monitor voltage while driving via a good OBD2 reader.)

2. CHECK CODES!!! if there's a CEL make sure it's fixed or at least NOT related to your issues.

3. Vacuum gauge testing. make sure there's no air leaks in piping/manifold and that the max has proper nonfluctuating steady idle when warm.
There's a lot that you can test with a simple vacuum gauge:
http://www.tuneruniversity.com/blog/...-vacuum-gauge/
http://www.gregsengine.com/using-a-vacuum-gauge.html

4. check fuel pump and fuel connections, fuel hoses for leakage, o-rings on fuel rail and at each injector for pooling fuel, leakage.

5. check if your max has the dreaded FPCM Fuel pump control module. (limits current to the pump) if it does, rewire it with doing #6. and #7.

6. make sure your fuel pump has a good dedicated chassis ground spot, instead of the ground that runs inside the harness

7. run a larger gauge wire (12-14ga) from a dedicated fused RELAY to the fuel pump +12V = this will ensure the fuel pump will be getting enough power in all RPM ranges, and will prevent current drop (resulting in less fuel pressure) especially at higher RPMs. A MUST MOD FOR A BOOSTED MAX. (I have 3.5L and this mod was very helpful for consistency in tuning)

8. tuning device = make sure all fuel offset settings are exactly consistent and you do not have a target map value that's pulling fuel out or an overlapping map that's resulting in less fuel. If you do not have a tuning device, get one and tune the car (especially with a 3.5L swap with 3.0L timing)

9. Wideband O2 sensor = they die (make sure you replace exactly with the type you need LSU4.0, LSU4.2, LSU4.9) especially if you had it on a car that was running rich. Wideband will read wrong because sensor is not reading exactly what it needs.

10. COLD START = IACV + Coolant temp sensor. After first startup the ecu dumps more fuel for extra air coming in via IACV (idle air control valve) until the coolant temp sensor tells the ECU the engine is warming up and it will begin to lean out that extra fuel until engine RPM stabilizes at 750 and coolant temp stabilizes between C and H. If your IACV is not working/not hooked up the leaning out is related to the engine getting warmed up.

11. Adjustable FPR. If you have an adjustable FPR, make sure it's not inline with the stock FPR in the fuel rail (but replaces the stock FPR), or IF you're running a NON-RETURN fuel setup, by returning extra fuel to the tank via FPR and return line, check your fuel path and what the STATIC fuel pressure is set on FPR.

Kretzmech

iTrader: (1)

Thanks for a great answer!