So this past weekend I was driving home, accelerating in 3rd when all of a sudden I got a horrible misfire. So as soon as I felt it, I killed the car and pulled over. I came from the MK3 supra world so I carry a small arsenal of tools with me. So The first thing I did was rip the plugs out. #2 was completly pushed against the plug tip (NGK BPR8ES gapped at .25)

Initially I thought something had hit my plug and that i was going to wind up with catastrophic failure. I had a spare set of plugs with me so I threw them in and started it up. Ran fine ?

I nurse the car home and the next day I go to bring it to a friends shop. The car starts studdering violently and wont idle. I come to a stop and the idle starts to climb to 2000-2500 and bounce up and down.

So I start in with diagnosing the problem .I did a compression check, all around 130. So I stick a magnet in the cylinder, nothing

Then I get to thinking its my meth failsafe somehow gone haywire. So I completely unhook the meth failsafes and shut the meth off, eliminate the boost bypass solenoid and try again. Car runs like normal again.

I go for a quick test drive, car boosts fine. I come to a stop, and the idle drops to 3-500 and slowly catches again. I try another drive without boost, Car drives perfect for a few hundred yards then all of a sudden it falls on its face, sounds like a WRX, idle drops and the car feels like its going to stall..but then catches itself and is perfectly drivable again ?

Cliff notes...
Misfire leads to car stumbling and sounding like WRX while driving under normal conditions, but then catches itself and is fine.
Compression OK
New Plugs
New Oil
Meth unhooked
Failsafes bypassed.

Any insight would be appreciated.

 

it sounds like an o2 sensor since full throttle open loop ignores the o2 sensor and doesn't stumble, but on part throttle closed loop the ecu is using the o2 sensor and your getting a stumble.

Maybe someone else can pitch in?

edit: also, maybe you detonated bad enough on a stumble that it crushed the plug?

 

boost leak??

 

I did a boost leak test the day before this all happened. Only thing leaking is my TB seals, but those have been leaking for quite some time.

 

Sounds electrical. o2 makes sense since your ecu could be getting a f'd electrical signal from it.

 

Go back and do a leak down test on the Cylinder's. 130 sounds a little low to me. IIRC, 165-170 is normal.

 

I'll do a leak down next. The compression seemed a little low to me too but I wasn't too worried about it since they were all within a couple PSI of each other.The car showed no other symptoms of low compression either.

I threw a code last night while I was looking at it so Im goin to pull that and see what I can find.

 

any luck with the code... you should pull the timing belt cover and check cam timing.

 

I will when Im out of work. I'll dbl check the timing as well but Id hope its not off as I have fixed gears.

I did the T-belt, water pump, and all pulleys at 58K miles ( Car is at 61 now). The car has cams, but stock gears.

 

Well the code reader wasn't much help. "Random misfire detected"

I could of drawn that on my own.

The EGR EVA O2 and CAT lights are blinking as well.

Im going to rip my 02 sensors out and check them / test them and go from there.

 

New development

So I pulled my coil and plug wires. I was looking inside the coil boots for rips and I looked into the coil for cylinder # 2 and the metal sleeve that goes onto the tip of the plug is GONE. No where to be found.

So my conclusion... #2 coil controls cylinder 3 as well.. Since it was barely touching the plug that explains my intermittent problem.. and if that coil isn't firing, neither is #3.. So no 2/3.. WRX noise ?

I ordered 2 new coils and I'm going to try a friends tonight to see.

 

Yeah our cars are batch fire 1/4 and 2/3 aka wasted spark iginition.

I'll bet you the metal tip came off when you changed plugs it happened to me and i had to order a set of wires .

 

Problem solved.

I stole my buddys 9 coil/wire. They dont fit perfect but I crammed them on there. Car runs tit's.

Looks like the coil **** it's pants, caused the misfire/detonation. Crushed the plug. Intermittent failure. 2 New coils, plugs, wires en route.

 

damn awesome troubleshooting ftw and fix