Hey all,

I just picked up a 2012 Evo X MR that is, allegedly, stock drivetrain and it consistently hits fuel cut / overboost at or above 5k rpms. This in turn caused a p0234 cel. I have carefully checked the boost control solenoids vacuum line routing and condition. They appear correctly ran and there was no obvious sign of cracks, looseness, leaks, etc. I also checked the fpr vac line and it is securely attached with a clamp on the fpr side and a zip tie on the plenum side. I also checked the intercooler piping and all is securely tightened and again, visually there are no issues. Finally, i checked a couple of grounds on the driver's side frame rail and cleaned them up just to be absolutely sure they weren't somehow contributing to the overboosting (as far as causing an electrical problem with the bcs).

i understand that it could be a bad tune installed by a prior owner but besidea that is there anything I can easily check?

Thanks all!

 

So no drivetrain mods, but what about fuel system mods? Also, has the car always done this or did it just start? Do you know if the previous owner tuned it? - and if so - was an open source tune or a cobb AP tune?

 

I was told that besides some exterior cosmetic mods it was completely stock. The injectors appear to be oem but I did not check the fuel pump.

I bought the car Wednesday and it did it on the way home from the dealership. When I called them they said it was either a bad spark plug or vacuum line.

I do not know if it has a tune on it. I have a tactrix 2.0 cable along with evoscan and ecu flash but I cant get it to download the file / rom that's on the car now. I tried opening a stock rom in ecuflash and it says it cant find the definitions or is not recognized. Something along those lines

Thanks for the reply!

 

You will have to add your car's definition file to ecuflash. If you google around, you should be able to find it. Did you pull down the DTC with evoscan v2.9 or v2.8? If you used 2.9 install 2.8 and pull the code down again. 2.9 can be a little buggy when it comes to the DTC's and can provide the wrong code sometimes. I don't see how a bad sparkplug can cause overboosting. I'd first guess its either a stuck/broken wastegate, boost-solenoid, vac line or tune related. The car was probably modified at one point and rolled back to stock before selling.

 

So, I ended up picking up the Cobb Stage 1+ kit and discovered that sure enough my Evo was already tuned. So, I installed the Cobb SF intake along with my AP and uploaded the Cobb Stage 1+ tune. However, instead of overboosting, since installing the Cobb parts, I am only hitting 14-16 psi of boost and it quickly falls to 10 psi by redline. I have no idea what's going on. I performed an intake leak test today (built a tester that attaches to the metal turbo inlet pipe and I'm using a large compressor w/ regulator) and I found that my FPR line was loose and was leaking under pretty much any pressure. I fixed that with a new line and zip ties and thought for sure that was my issue as I retested up to 20 psi and could not hear/see any other leaks. I went out and did some logging and I was wrong, it does the EXACT same thing. It hits about 14-16 psi and then falls to 10 psi very quickly. I've replaced my stock BCS with low mileage used ones, including the vacuum lines to the inlet pipe and up until the T fitting that goes to the j-pipe and the wastegate actuator. I replaced those lines with new vacuum lines as the original ones were looking a little crusty. Does anyone have any idea what could be causing me to only hit roughly 15 psi peak boost? My next step is to check the wastegate actuator itself to see if it's physically loose and then do another intake leak test but I really didn't hear anything else besides air moving through the valvecover after replacing the FPR line. Very frustrated. Thanks everyone. I've attached my most recent datalog from today if anyone is at all curious.