Autonerdz forums

carl- its partual misfires that you can feel with your hand at the tailpipe, when put in drive or turn headlights on it goes away, its a mystery that i've always wanted to know...your saying the overlap can do it? it sounds like an injector issue but its not, my car does have an injector issue now because one of the multecs started to short and i replaced it with a direct replacement napa injector which i later found out has a 10% flow difference at low dutycycle, they wouldnt give me my money back, in future im gonna put a linder flowed set in

Ok Earthlings, so here's another set.

This vehicle is an 01 Nissan Maxima 3.5.  Towed in barely running, horrible surge.  Multiple codes, including MAF.

According to what we can find this is not a frequency style maf, according to Alldata it reads direct.  Scan tool shows a voltage reading for MAF, which at this time was 1 volt, flat line, connected or not.  Even though it said disconnecting the MAF should straighten stuff out, it did not.

First capture shows the MAF is indeed dead, milliamps never changes.  Frequency is bouncing around a lot, but according to Tom that will be addressed soon.

Since the vehicle was surging so bad, like a rev limiter, we decided to see what the injectors were doing.  Second capture shows the volts to injector #1 while the vehicle was surging.  Intereting the way the PCM mostly shuts down the injector.

Third capture is simply a zoom on the second, shows things in a bit more detail.

Fourth is after repair with a new MAF. The milliamp reading does indeed move directly with the volt reading.

A: MAF volts
B: MAF milliamps
C: MAF frequency
D: Injector #1 volts

Something a bit odd in the capture, the ranges on the side show that is the way it is hooked up.  Of course the top shows what it wants, as usual!  But the volts and the frequency are a total and direct match.

John and Mike

Carl

We did choose a frequency range.  There were only 2 available, and I don't remember auto being on the list.  I have already sent some of the stuff off to Tom about that part.  This post was intended simply to show what a maf that uses direct voltage looks like with the microamp probe.

The problem we have now is that, as you are aware, you cannot get to frequency unless you physically have the scope hooked up, and I ain't going to work on a sunday to get it!  During the week we will continue to follow Tom's advice on what we need to do to get this info to pico.

thanks

john