Replaced MAF sensor - now it wont start

Hey all,

My '08 Legacy GT started having issues the other day. I got on the highway and noticed that I was lacking in power. Got to a red light and car started shaking and acting like it wanted to stall out and check engine light went on and cruise control was blinking. I happened to be right down the street from the Subaru dealership so I brought it in and the guys told me it seemed like it was a vacuum leak (which I had presumed myself) so I brought it home and took everything apart that I could, put it back together nice and snug.

I took it out for a test drive and there was no difference. Check engine light went on. Hooked it up to the Cobb and checked the codes. Everything pointed to MAF sensor, vacuum leak, O2 sensor etc.... Also cylinder 1,2,3,4 misfires.

After this I was pretty convinced it was my MAF sensor, seeing I had already suspected it was going bad based on some previous other strange, random behavior. The common test I used was, turn the car on and while its idling (badly), pull the plug off the sensor. If it turns off, the sensor is good. If it continues running and the idle bumps up and it runs better, the MAF is bad. Result: The car stayed on and actually idled quite stable.

I went and bought a new MAF direct from Subaru, installed it and the the car would continue crank, turn over and immediately shut off. This is what I did to troubleshoot:

1. Pulled the plug off the MAF and attempted to start. The car turns over right away and has a stable idle.

2. Connected the Cobb AP and reset the ECU. Plugged the MAF back in and attempted to start. Turns over and immediately shuts off.

3. Unplugged MAF, pulled the ground cable off the battery and let sit for 30 minutes. Plugged MAF back in and tried to start again with the same results.

4. Put the old MAF back on and tried to start and has the same results as the new one. Before putting the new one on, I didn't had a problem starting the car with the old MAF on. Now it wouldnt start at all.

In every scenario, the car always starts and runs with the MAF unplugged. Based on the issues, I don't feel like there is a mechanical or electrical issue here. I feel like it has something to do with the ECU recognizing the new hardware, but I could be wrong.

Any help would be greatly appreciated all!

Thank you!

Tony

I have seen posts suggesting that the wiring harness to the MAF and the connector pin can also be a source of problems. I have experienced odd issues when removing the MAF to clean and putting it back on. Unplugging it and reconnecting it seemed to work.

Here is a link the post and link to a replacement wiring harness/connector for it from i-wire

Connecter is known to go bad:

https://legacygt.com/forums/showthread.php/faulty-maf-sensor-connectori-255914.html

I-wire.com makes a replacement connector with pigtails for easy splicing

https://www.iwireservices.com/product-page/maf-plug-02-07

Don’t concentrate on only the MAF. When you unplug the MAF it puts the ecu into an open loop map so it ignores the sensors and runs a preset map. Sort of a limp mode. Check your upstream o2 , blue T (if 08 has one) , and your OCVs.

Also what codes did you have?