Need help with a Subaru motor

Johnny

Johnny

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First off thanks for reading. I have a freshly built 2.5 double overhead running a turbo and a aeromotive fuel pressure regulator , My computer unfortunately is a microtech and not many tuners deal with them, I upgraded to a bigger turbo and bigger injectors and had to retune the computer . My Issue : The car runs great and as soon as it  hit's 20 to 25 minutes it starts to stumble Big time ,I have replaced every coil,all the sensors,new spark plugs, new fuel pump & filter,adjusted fuel pressure, also made sure fuel tank is vented, checked all my connections,installed new relays on the computer and much much more. when it act up and you keep your foot into the pedal it starts to buck you back and forth in your seat. When it cools down you can drive it and it runs perfect until that 20 to 25 minute  mark and all hell breaks out. Does anyone have any ideas I can try ??.  

                      Thanks 

            Johnny

 
Something is obviously getting hot then cutting out.  Where is your computer located?  Is it getting hot?  Do you have a infrared thermometer?  When it gets hot and starts cutting out, you need to take temperatures of all of your sensors, PC, connections.  Find out what is hot and you could use a can of compressed air duster and turn it upside down and spray one thing at a time and see if you can locate the part that is getting hot.  Do you have a fuel pressure gauge?  Proper fuel pressure would be the first thing to check, then spark.

 
HTElectrical said:
Something is obviously getting hot then cutting out.  Where is your computer located?  Is it getting hot?  Do you have a infrared thermometer?  When it gets hot and starts cutting out, you need to take temperatures of all of your sensors, PC, connections.  Find out what is hot and you could use a can of compressed air duster and turn it upside down and spray one thing at a time and see if you can locate the part that is getting hot.  Do you have a fuel pressure gauge?  Proper fuel pressure would be the first thing to check, then spark.
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Thanks HT for the reply, My computer i believe is not getting hot I have had it in the same place for 12 years, I will try your idea with the temp gun, I figured it was going to be one of the sensors or coils but I have changed all of them, I do have a fuel pressure gauge and that's spot on, I have been troubleshooting it now for about 3 weeks and don't know what else to check, I did install a stand alone fuel pressure regulator on this new motor and a few other things, like a intercooler & fans & a bit bigger turbo & had it tuned , The tuner said it didn't act up when he had it on the dyno.I will keep picking away at it .thanks again .

           Johnny 

 
You need to validate what the fuel pressure is doing at this time. I see that you changed everything and that is great however, if you validate the fuel pressure drops then you can tackle the fuel system. I ran into a similar issue and ended up going through 2 fuel pumps, since i changed it I looked everywhere else but once I actually checked fuel pressure under a load and it dropped to zero then I knew. If the fuel pressure remains where it should then you know to check ECU/ignition. Could be a bad ground somewhere as well.

 
TGSRacing said:
You need to validate what the fuel pressure is doing at this time. I see that you changed everything and that is great however, if you validate the fuel pressure drops then you can tackle the fuel system. I ran into a similar issue and ended up going through 2 fuel pumps, since i changed it I looked everywhere else but once I actually checked fuel pressure under a load and it dropped to zero then I knew. If the fuel pressure remains where it should then you know to check ECU/ignition. Could be a bad ground somewhere as well.
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Thanks for the tip, I currently have my car at a friends house who is taking a look at it for me, You make a good point. I thought about attaching my gopro camera to record my fuel pressure gauge that is mounted to my fuel rail. I will try this .

           Thanks

 
I had a Subaru that would act up hot. Not bucking but cut out like a rev limiter. Tried all sorts of remedies like you. Even sent the ecu to the manufacturer for inspection. Nothing helped. Almost gave up on it when we were out at the dunes talking to a fellow Subaru guy. Said John had a similar issue with his car in the dyno.   He said to try putting a flat washer under the cam or crank sensor. Bam! Problem solved, no cut out. 👍🏻Something to try. ?
Also I’ve had one Subaru get weird on me and ended up being a bad alternator causing electrical interference to the ecu. 

 
BJ_buggyfab said:
I had a Subaru that would act up hot. Not bucking but cut out like a rev limiter. Tried all sorts of remedies like you. Even sent the ecu to the manufacturer for inspection. Nothing helped. Almost gave up on it when we were out at the dunes talking to a fellow Subaru guy. Said John had a similar issue with his car in the dyno.   He said to try putting a flat washer under the cam or crank sensor. Bam! Problem solved, no cut out. 👍🏻Something to try. ?
Also I’ve had one Subaru get weird on me and ended up being a bad alternator causing electrical interference to the ecu. 
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Thanks BJ buggyfab.

  You may be on to something, It's strange but while the motor is running and you just lightly tap the crank or cam sensor the motor will shut down, I thought i was onto something but, I  tested this theory on 3 other cars now ,And every time you just give those 2 sensors a tap ,the cars all shut down, I could tap them with just my finger and i could get all 3 of them to shut down, I thought that was really strange. Thank you so much I now have something else i can try. I will also unplug my alternator and try that. Thanks so much for the reply, I would be interested if other subaru guys could run this 1 minute test by just taking a small back of a screwdriver handle and while the motor is running just tap the cam or crank sensor just so lighty and see if there motor shuts down. This washer trick or alternator trick just may save my weekend . I will let you know one way or the other 

 
Well after 4 weeks of troubleshooting and cursing , I found a bulletin that Subaru posted I believe in 2013 and it was my fix , I would of thought that someone here running Subaru motors would of come across this same  issue I had. Boy I am glad this issue is resolved . Thank you Bj buggyfab for your post, After your post I went in deep on the webb and found this bulletin.https://subaru.oemdtc.com/592/difficulty-starting-rough-idle-cam-position-or-misfire-dtcs-p0340-p0341-p0345-p0346-p0365-p0366-p0390-p0391-p0301-p0302-p0303-or-p0304-2011-2014-subaru.

   Hope this will help someone in the future. Subaru sells the shim kit.

                Johnny

 
Johnny said:
Well after 4 weeks of troubleshooting and cursing , I found a bulletin that Subaru posted I believe in 2013 and it was my fix , I would of thought that someone here running Subaru motors would of come across this same  issue I had. Boy I am glad this issue is resolved . Thank you Bj buggyfab for your post, After your post I went in deep on the webb and found this bulletin.https://subaru.oemdtc.com/592/difficulty-starting-rough-idle-cam-position-or-misfire-dtcs-p0340-p0341-p0345-p0346-p0365-p0366-p0390-p0391-p0301-p0302-p0303-or-p0304-2011-2014-subaru.

   Hope this will help someone in the future. Subaru sells the shim kit.

                Johnny
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Awesome! Glad it helped. Did not know Subaru had a TSB on it. 👍🏻

 
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