I have a STM built and STM tuned car but they are to far to get it checked out looking to fix in house. Car will spool and hit 34 psi and then bucks like hitting a wall. I changed plugs looked over vacuum lines, changed plugs and checked for boost leaks up to 30 psi and there isn't any. When car hits 34 psi the wideband reads 10 which is rich as hell. Would a small leak that I'm not finding cause this or is this a tune issue? Any advice would be great help, thanks!

 

Sure as heck sounds like a boost leak to me.

How long has the car been running fine on the tune prior to this happening?

How are you testing for boost leaks?

 

The car was running fine for awhile up to the point of when I got the car painted. Then the car sat for a year and the battery died but I never heard of AEM resetting itself. I tested with a home made PVC cap with a compressor hook up in it and put it on the inlet of the turbo

 

Well 2 things. You're only testing to 30psi, and the car is seeing more than that. But the car sitting for a year could be problematic.

Did you use soapy water, and look/listen/feel all the couplers?

 

I did not use soupy water. I just listened and fixed the spots that I felt air or heard air coming out. A friend told me it could be a map sensor

 

I'm assuming you're on AEM since STM tuned it, what's the boost cut set to? What are you running for ignition setup and what did you gap the plugs to?

 

Get a spray bottle with soapy water in it, and spray your clamps. Then check for leaks. You'll be surprised at what you find... especially at higher boost levels.

It could of course, be a hundred things... but that doesn't mean you skip over the obvious things first. Troubleshooting is always going to net more than throwing parts at the car.

 

I did the boost leak again there is no boost leak. Plugs got gapped as the same STM left it at. I had couple of buddies look at it and all things but tune have been ruled out. Going to have to call STM and see if they can fix it before I go back to Texas where I'm stationed

 

Good idea to have tuner take a look at it. On a side note, you've probably checked during you boost leak test, but have you checked your throttle body seals? It can be subtle but make a difference at 34 psi.

 

Car sat for a year and I don't see anywhere you saying you drained and replaced the gas. Sounds like some bad detonation on some old gas.

 

I agree with having your tuner look at it, but consider that you're talking about a computer.

If the tune was working fine for x amount of miles, and now all of the sudden isn't working, it's unlikely that it will be the tune, and more likely that it's a boost leak that you haven't been able to detect, spark blowout, or as coke mentioned, some crappy fuel.

Anyway... keep us posted once you find out.

 

Car got stored away empty and I filled up with mobile. Tried switching out map sensors last night didn't work. Read that a bad map will cause what I have.

 

Have you checked what the boost cut is set to?

 

I have not but from locals and stuff was saying AEM was detecting knock and it stop the car from going. Sounds reasonable because if the car bucks if you keep on the gas it won't go past 5,500 rpm and bucks till you get off the gas. Ill hook the laptop up and see if I can find the boost cut settings

 

Knock control will not stop the car from going. Check what your 2 step rev limit is set to, the settings that control it's on/off state could be off as well....but that shouldn't have changed randomly on its own.