I've been getting the engine code for "Multiplicative Fuel System Too Lean" for some time now. I have verified that I'm not getting any unmetered air in.

Today I replaced the fuel pressure regulator on the injector rail, and also added a connection for a fuel pressure gauge. Unfortunately I didn't get a reading with the old regulator, but with the new one installed I was getting 3.1 bar with the vacuum hose on the regulator connected properly, and 3.8 bar with it disconnected.

According to the specs I've seen, my engine code uses 4 bar fuel pressure into 284cc/min injectors (also, my FPR is stamped 4bar).

- Should I assume that I have either a clogged fuel filter or bad fuel pump since I'm getting lower?

- Is there supposed to be a check valve on the vacuum hose from the FPR to the manifold such that only ambient or boost pressure gets to the regulator? It seems like the vacuum connected as I have it takes the pressure down quite a bit, though that may be on purpose to make idle injector PWM more fine-grained.

FWIW, the car is a 2001 A4 quattro wagon 1.8t.

Thanks!

 

the injectors are pretty known to go bad (or so im told) and im pretty sure the inector sets are cheaper than the fuel pump! have u used an addative to clean the injectors? maybe try the additive and use the shell vpower drive about 30miles highway and see if that helps. if it doesnt i would just swap the injectors out.

 

Ah I should have mentioned: yep, the first thing I did after an air leak check was to replace the injectors, then the MAF and MAP.

 

fuel filter might have a hand in the problem