Why do people replace the ecu, when the failure rate of ecus are almost null. Why won't you try replacing the MAF? A used one is just as cheap as an ecu and its like a five minute job. Seriously tearing apart the wiring is very unlikely to help.

Why do people replace the ecu, when the failure rate of ecus are almost null. Why won't you try replacing the MAF? A used one is just as cheap as an ecu and its like a five minute job. Seriously tearing apart the wiring is very unlikely to help.

Because it does the same exact thing if the MAF is disconnected entirely. And when the MAF is hooked up it reads grams per second just fine on the scanner graphs.

 

Without the MAF the ECU is going according to TPS and O2 sensors and it still has the loss of power like something is loose.

 

Was only $30 for the ECU, now they can eBay the new one.

Still doesn't make sense to change ecu for no real reason and not try the MAF. I also beleive there was also mention of another viable problem wich is the main relay, another simple part to change that doesn't cost much used. Sometimes you can over diagnose things, you have thrown tons of time into and still ended up changing parts that don't need to be changed. I'm sorry I just don't get the reasoning.

Edited January 7, 201610 yr by mikaleda

Also since MAF sensors are a common issue on these anyway. It would still have made more sense to replace it just because if it isn't bad now its very likely to fail later whereas the ecu practically never fails on a Subaru. Just saying

Edited January 7, 201610 yr by mikaleda

Still doesn't make sense to change ecu for no real reason and not try the MAF. I also beleive there was also mention of another viable problem wich is the main relay, another simple part to change that doesn't cost much used. Sometimes you can over diagnose things, you have thrown tons of time into and still ended up changing parts that don't need to be changed. I'm sorry I just don't get the reasoning.

The Main Relay is a double pole single throw switch, I probed both poles on the switched side and it stayed right at 14v while the car was driving and the hesitation was occurring, I had the meter right there on the seat next to me while driving and engine was hesitating/delivering no torque. So why would I replace a relay that is working fine?

 

I had a good reason to believe it was the ECU, the injector pulses were going almost non-existent when the short term fuel trim reading was in the positive. It does this with or without the MAF.

 

The ECU is a complicated device that is impossible to probe for every possible problem internally, but a relay can be probed.

 

So you are saying the ECU will occasionally cause the lean condition by cutting it's fuel pulses short when the MAF is not hooked up? Or is hooked up but is malfunctioning?

 

Something else is shorting or confusing the ECU.

I just know that MAF fail alot more often than ecus, in every thread that I've seen someone replace an ecu its never fixed the issue.

If you are, were charging for labor time for all this diagnosis it would already have paid for the two most likely culprit parts that are known for failing. I'm just saying that sometimes it doesn't hurt to swap an easy to get to part that has a common history of failing rather than spend hours of time diagnosing it to just replace a part that wasn't a problem.

Id hate to bring up this dead thread but did you by chance every figure out what the issue was? It was just kind of a brick to the face reading this and eventually the problem was never solved.. or at least stated, this was a pretty helpful topic btw.

Nah, they sold the car after something else broke that they didn't understand, so they bought a minivan. I didn't check to see what the new problem was.

 

My guess is the old problem was something in the wiring harness like ABS computer, or cruise control, or some other module was sending bullshit signals to the ECU to cause the ECU to cut fuel pulses.

 

Or it might of been a sensor on the engine side. I kept telling him to replace the 16 pin engine-chassis connector with a new connector, in order to bypass the corroded and questionable connector problem, but he didn't want to do the work.

Edited May 17, 20169 yr by White95Legacy

thanks for getting back to me, i am having the same problem as well with the fuel cuts at lower rpm w/ hesitation underload its odd and throwing me for a loop. It almost seems like its in limp mode i cant tell because i dont have a instrument panel in my buggy lol