Bradyy4

So, about 3 months ago, my turbo TC randomly decided to start misfiring around 6 psi. It is set up for 11 psi. I bought the car with the turbo kit already on it and the car ran great, very quick. The problem progressively got worse and worse. Recently it got to the point where I could barely drive it because it was misfiring so bad. That's when I brought it to 2 local performance shops. The first one couldn't even figure out how to connect to my AEM FIC...told me to figure it out myself and then bring it back to them (I had no intentions of going back there), the 2nd shop told me they thought it just needed to be tuned and it would fix all my problems! Well, they charged me $130 to TRY to tune it, and fail. They said they couldn't tune it because they weren't getting the proper signal from the MAF? Told me to check the wiring from the FIC and to the ECU and to the MAF. All looked good and all was reading same voltage... Called AEM and they said it sounded to them like everything was working right and recommended I load a base map and try to get it running like stock without getting into boost, and then add fuel/timing from there. Loaded a base map, and it still misfires like a ****.
Sooo, here's all the stuff I've tried myself
-Replace MAF
-Replace Cam sensor
-Replace PCV valve
-Bring it to shops to get tuned/diagnosed
-4 different sets of spark plugs (dif heat ranges)
-Boost leak test
-Took the whole turbo setup off, intake manifold, etc and put it back together because I got bored (when I put it back together, it ran a lot better overall, but still misfires often and under any amount of load)
-Checked coil resistance and wiring (found some bare wires near coils, taped them up so they didn't arch on the valve cover)

CAR SETUP:
2006 Scion Tc
Turbo Toyotas turbo kit
Garret .82 ar 57 trim t3/t4 turbo
AEM FIC
Stock internals
NGK BKR7EIX spark plugs
Ptuning exhaust
Spectre air filter

This problem has been giving me hell for months, and I haven't been able to race, which KILLS ME!!! I'm desperate. I'm open to suggestions and I'll answer any questions.

BTW, I ADMIT, I'M NOT A PRO WHEN IT COMES TO TURBO CARS!!! I AM A MOTORCYCLE MECHANIC AND I'M FAIRLY NEW TO THE CAR SCENE! BUT I'M WILLING TO LEARN IF YOU CAN HELP ME OUT

my06tc

iTrader: (2)

did you get a CEL and did you read the codes,what cylinders were it misfiring from

Bradyy4

Just the Random misfire code.

DaTRican

Test your crank positioning sensor?

my06tc

iTrader: (2)

did you take out your spark plugs and check the gap

my06tc

iTrader: (2)

pretty sure those spark plugs you have comes pre-gapped at .30.......just make sure there not any higher,ive seen scions that misfire and it wound of being the spark plug gap,

burgandybomber

iTrader: (1)

If the plugs are for a Tc they should come gaped at .044. I had to gap mine down to between my .025 and .030 wire.

2T0neTC

Does it misfire when you're on the freeway in 4th or 5th and when you floor it and the wastegate starts to open, does it well, missfire? sorta like bogs down? Mine did that a LONG ___ time ago, just turnt up the boost 2 psi and it was gone. It did it again recently but I had a good tune put on it for 8 psi and no pops or missfires.

That_Kid_Ju

BKR7EIX comes pre-gapped to 0.032" (the -11 is gapped to 0.044"). Were the plugs fouled when you changed them? Fouled plugs means too much gas being dumped (tune related). Do a leakdown test to make sure valves are okay and headgasket. Other than that, it's likely tune related (MAF table or MAF clamp maybe).

Bradyy4

New Plugs Are Gapped To .030". Plugs Were Really Lean, But Fixed The Lean Problem Already...Now The Plugs Look Good.
How Do You Test Crank ShaFt Sensor? Tested Resistance But Idk What It Is Supposed To Read. That Was Gonna Be My Next Step.

my06tc

iTrader: (2)

is it possible to upload a video.....hows your afrs at idle and when it misfires

Bradyy4

AFR at idle is around 14.7 and under normal driving 12ish. Backfires constantly. Even while idling. I ordrered 4 new coil packs, will update when I install them.
Next I'll probably buy a new crankshaft position sensor (although it isnt throwing a CEL)

Bradyy4

UPDATE: Installed all 4 new coil packs. Fixed the problems. Now I just have to adjust the fuel map a little and should be good to go

criminaltc

Yeah I just got into this thread, and I noticed in the original post of things you replaced, you didn't mention coil packs... that was silly. Haha. Glad you got it man.