[s-cars] UrS4 running Lean fuel mixture

Dave Tremblay da_trem at hotmail.com
Fri Feb 13 11:54:30 PST 2009

 I just swapped the fuel pump with a good oem unit. Same damn result! At this point i'm really suspecting a bad maf..everything fuel-wise as been changed.
Next week i'll try another maf(RS2). Until then, i will continue searching the problem.
> From: blade.dawn at mac.com> Subject: Re: [s-cars] UrS4 running Lean fuel mixture> Date: Fri, 13 Feb 2009 11:29:25 -0500> To: da_trem at hotmail.com> > Dave,> > Do the volume test, it's more critical, even a weak pump will > build up pressure eventually. Call if you need details.> > Bruce Everett 574-935-4767> On Feb 13, 2009, at 10:20 AM, Dave Tremblay wrote:> > >> > Hmmm, interesthing i'll check the M5 forum..> >> > Pump is seeing 13.5+ volts all the time(its relayed to the battery)> >> > Injectors are still the stock ones and they have quite a alot of > > mileage.> >> > I need to do a pressure test to see what the walbro unit feeds to > > the motor...i dont know if its me but the whining from the pump > > seems louder than before..i'll do the pressure test!> >> > I've just tested another wideband sensor and it hasent changed a bit.> >> > Until thats fixed,i'll stay off boost!!> >> >> >> >> > Date: Fri, 13 Feb 2009 05:29:12 -0800From: > > mikellardizabal at yahoo.comSubject: Re: [s-cars] UrS4 running Lean > > fuel mixtureTo: s-car-list at audifans.com; da_trem at hotmail.com> >> >> >> > Interestingly enough, there's a discussion thread in the BMW M5 > > forum about MAF's going bad.Although the Bosch Maf in the e34 M5 & > > Porsche 928,911's of the 90's are similar to the UrS4, its not the > > same unit, but the metering is similar.When the Bosch MAF goes > > south,usually attributed to age, it loses the ability to maintain > > the voltage needed to send the ECU the right signals.,thus > > allowing the car to run very rich at idle and around town driving. > > Once at the 5-7500 rpm range a bad MAF can go dangerously lean. One > > guy put a hole right through his M5's block. So its kinda odd that > > you're just lean all the time.Hmmm...Couple of things to > > check:Battery voltage :Voltage from idle to load. ( You need at > > least 14+ volts @ WOT IIRC ) The Walbro might be voltage starved > > giving impeded flow.Stick a FP gauge before the rail.Make sure > > you've got at least 4 bar.Injectors ? a bad batch of dirty gas can > > really do a number on flow rate. FWIW- You're running scary lean at > > boost. I'd keep the revs> > under 5K for now.Walbro's are a hit & miss FP. Q control is > > moderate at best. Ask the Subie guys.Good luck.> > _________________________________________________________________> >> > _______________________________________________> > S-CAR-List mailing list> > S-CAR-List at audifans.com> > http://www.audifans.com/mailman/listinfo/s-car-list> 

More information about the S-CAR-List mailing list