wayner845

iTrader: (2)

Ok its a 2003 uk sti 37000 miles and without too many details i have recently fitted fmic ,agency power fuel rail kit 650 injectors from 720's ( injector change reason, trying to get rid of hesitancy) .It was running fine off boost with the fmic but has since been off the road awaiting the 650's .Anyway today i put it all back together with 650's and it started no probs but then stalled almost immediately and then started it again but again was struggling to tickover or rev.Checked everything over ,wires,fmic connections ,vacuum hoses etc etc .Eventually i diconnected the maf and started it and low and behold it runs fine diconnected,is it that simple i need a new maf ,do these things just die.
The car has not been mapped with the fmic and has only done about 6 mile with it fitted,i have been waiting for the 650's before i go back to Bob R for a tweak.
Good place to get a Maf,how much are they.
Any help appreciated.
Wayne

wayner845

iTrader: (2)

Splitpin

We can't tell you for sure whether you need a new airflow sensor. If you don't have any method of checking it directly (i.e. DeltaDash/etc or a voltmeter between its output pin and ground) then the only thing you can do is replace it and see if it fixes your problem (or look elsewhere and see if you can find a cause, for example a mistake you've made putting things together allowing unmetered air into the induction tract).

They rarely "just go", they normally misread for a while first - although it's always possible to get an outright failure.

New sensor for yours, either Subaru dealer, or somewhere like here.

wayner845

iTrader: (2)

Do you know why it runs fine when diconnected .Can the car be driven off boost whilst diconnected.
Ive just checked everything twice underneath the lot cant find anything,the only thing i didnt mention was the bty has been off the car in the garage on trickle charge for weeks .
How do i do the voltmeter test.
Thanks in advance.

brocksta

iTrader: (1)

370,000 miles, wow,thats alot on an 03 plate.

wayner845

iTrader: (2)

37 k one to many 0.

Splitpin

It doesn't "run fine". If you disconnect the MAF (so the voltage going into the ECU disappears), the ECU will work on the basis of a specimen value sufficient to keep the car running. If you drive it around like that you will almost certainly find it's in limp mode.

Would avoid it if at all possible. As above you'll probably find it's in limp mode but it's better to be safe than sorry.

This is one of those questions where if you have to ask, you're probably not going to be able to do much with the answer, as you need sufficient experience in order to tell whether the output you are seeing is correct in any given scenario. Cutting the longer story short you just find the signal and ground wires in the MAF loom and put a voltmeter across them. Should see roughly 1.24 volts +-0.04 or so at hot idle. With the car in motion, as above you really need to know what it should be.

wayner845

iTrader: (2)

Cheers splitpin,i will have to leave it for now as i'm off to Oman early in the morn for 9 days.
I will strip it back a bit when i get more time and have a good check as i dont want to buy another maf until I'm a bit more convinced,


Thanks for your Help.

wayner845

iTrader: (2)

Ok guys found the problem,after much head scratching, fitted a new genuine subaru denso maf and the problem didnt go away .Anyway to cut a long stripping and reassembly story short this is what it was .I had reffitted the new maf tube (caik) 180 degrees round the wrong way so the air coming in was hitting the backside of the maf sensor.Yes i know numpty ,how i didnt spot it straight of i dont know but after many hours of scratching my head it just dawned on me as i was looking at it and new without doubt what i had done.Turned it round sorted lesson learnt .