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07 Wrx dies after 30 seconds consistently.

4K views 14 replies 6 participants last post by  Germz to Japz 
#1 ·
Lets just say I bought this 07 wrx off another mechanic who couldn't figure it out . Basically the car starts up and runs great then literally after 30 seconds every time it will stall right out almost like a complete fuel cut .
After a few days off test and trials here is what I have figured out .
1. Alternator puts out 14.7 volts which I believe to be high and I found unplugging the alternator the car ran for a solid couple minutes . plug alternator back in and car dies .
2. I tried two other tested good alternators and ran a new fat ground wire and that didn't fix the car .
3. I ran the car with alt unplugged and car jumped off my Volvo at 13.2 volts and the car will stay running . But I'm finding out that you can rev it great but then after 30 seconds but not exactly thirty seconds, but maybe after a minute and a half or so it will idle but pumping the throttle has a good one second delay till it will catch and rev up . shut the car off and runs great again just for the first minute .
4. finally the cel did come on but for system to lean and misfire in cylinder1 and 3, but these are a result of it switching to running real rough after a minute of perfect running .
5. Alt fuse is good . car came with a bad radio fuse but replacing it worked and didn't short out . also after a few minutes now the cruise light is blinking. everything else works.
If anyone has any ideas before I take the car to a auto electric specialist that would be great thanks
 
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#2 · (Edited)
The alternator voltage looks good. ~14 volts is correct and proper.
How about vacuum leaks or an improperly placed or just plain old broken MAF sensor? Kind of sounds like you are running too lean.
Do the AFR numbers look lean as well?
Any mods?
How is the fuel pressure at the rail?
Will it die if you keep the throttle open or does it only die at idle?

Sorry, you don't necessarily have to answer all of these but if it was a car I got into the shop this is somewhat how my thought process would go.
 
#3 ·
With the alternator plugged in it dies at 30 seconds every time . I replaced the alternator and it ran a lower 14.1 volts and stayed running good for 1.45 minutes . same when I run it unplugged it will run good for 1.45 minutes then it will stay running but will hesitate for a second when you hit the throttle. that's why I thought it was over charging related.
I will try another maf off my 02 wrx today and ill check the fuel pressure but I'm sure its ok for the first 30 seconds then maybe its like the computer then delays or sends weak voltage to the fuel pump or spark plugs. The af ratio stays at around 14.7 even when its trying to die.
 
#8 ·
As usual today again with alt plugged in, car starts up great and idles for 30 seconds and shuts off. And you cant save it. But I got a new P0410 code for air pump system . And attached below is another thread where someone says its only used for the first 30 seconds.? Could this all be a coincidental lead?
i tried unplugging it so far that didnt help.

http://www.clubwrx.net/forums/gener...valve-pump-issue-p0410-p1410-p2431-p2433.html
 
#11 ·
Well the car will run for a bit with the alt disconnected.
I'm thinking you have a really faulty sensor or a really bad electrical demon. I wonder if it's when its switched from open to closed mode that the problems really arise. I know you don't have any codes for them but how do the cam and crankshaft sensors and wiring look?
 
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