Pages: [1]
Author Topic: Maf sensor problem passat b5  (Read 534 times)
ettla
Newbie
*

Karma: +0/-0
Offline Offline

Posts: 5


« on: November 10, 2017, 05:23:58 AM »

I have a problem with my passat 1.8t
The engine stumbles anywhere from 1/4 to WOT with the maf sensor plugged in, i have tested 3 different maf sensors and the problem percists with either one plugged in.

If i unplug the maf it runs perfectly.

I went on to test the wires coming to the maf...

ground wire: i got 7-9 ohms to battery negative terminal, which i think is good
12 volt wire: i have momentarily 11.9v for 1 second as i switch on the ignition, but then goes down to 1.7volts...wierd?! if i start the engine i have constant 14volts on that wire, seems good?
5volt reference wire: have 4.95-5.05volts always with ignition on.

Signal wire: When the engine is running and maf plugged in,the signal wire is 1volt at idle and rises with rpm at light throttle i have seen as high as 2.5volts, still no throttle response above 1/4 throttle.

Im worried about the 12v wire being 1.7v with ignition on, engine off.
Could it be shorted to ground somewhere? I know other sensors share this 12v line, but i cant find a schematic for it, so i wont know where to look.

I bought the car like this and the previous owner knows nothing about it.
Starting to think its the ecu not recieving the signal, but ill have to look at the maf signal in vag com first.

So, what pin on the ecu is the maf signal input?
My ecu ME7.5 4B0906018AA
Logged
em.Euro.R18
Full Member
***

Karma: +4/-5
Offline Offline

Posts: 216


« Reply #1 on: November 14, 2017, 01:12:48 PM »

Id suggest looking to see if any current DTC's are set first before firing at the hip. Just because your passat runs better with the maf unplugged doesn't mean its definitely the maf or malfunction of the circuit.
Logged
ettla
Newbie
*

Karma: +0/-0
Offline Offline

Posts: 5


« Reply #2 on: November 27, 2017, 12:47:32 PM »

i have a log that shows the maf sensor is reading, but is not correctly responding above 25% throttle position.

MAF never reads higher than 18-19 g/s regardless of RPM or Throttle pos.

When MAF reaches 18g/s the throttle pos signal "HICKUPs" leaving a plateau in the graph...
Something is not right.
Logged
prj
Hero Member
*****

Karma: +214/-88
Offline Offline

Posts: 2921


« Reply #3 on: November 27, 2017, 01:56:15 PM »

You did a boost leak test, etc? Your intake is connected? Smiley
Logged
ettla
Newbie
*

Karma: +0/-0
Offline Offline

Posts: 5


« Reply #4 on: November 29, 2017, 05:51:37 AM »

This is a severe problem, i have checked all lines to the intake and they are connected. engine is almost stalling. It does not consume more than 20g/s of air when this is happening. At that load it is aproximately at atmospheric pressure inside the intake.
(160g/s@6000rpm@1bar above atmospheric
Engine idle is ~-0.5bar (160gs/6000rpm/1,5bar pressure range=0.018)
0.018*2000rpm*0.5 bar from idle=18g/s
Seems reasonable
Logged
Pages: [1]
  Print  
 
Jump to:  

Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Page created in 0.014 seconds with 16 queries. (Pretty URLs adds 0.001s, 0q)