davidward

I have a 2005 Scion tC. Over time. I get a misfire code. Sometimes i get the code and sometimes I don't. I cleared it a while back didn't have it for about 5 months, It came back for a couple weeks. Then cleared gone for a few months and now its back. Not sure whats going on.

INFO
I have the full Turbonetics kit with relocated MAF sensor.
2 steps colder plug with .29 gap.
10.5psi boost
Running 91 octane.

Symptoms:

Idle RPM bounces when left off the clutch. drops down to 500 then bounces up to 1200 a few times before it levels off at 800 but sometimes while its doing this it completely dies.
Sometimes with the A/C on the idle is around 500 which is way to low
I get a CHECK ENGINE LIGHT for random cylinder misfire among all cylinders, or random between all for cylinders misfire. P0300 code. Car runs good and pulls good just sucks when it comes to idle.

THINGS I HAVE DONE TRYING TO FIX PROBLEM

I have replaces a few vacuum lines.
Check compression reading 210 + or - 5 between all cylinders.
New spark plugs
Swapped coil packs at one time with another car and still got the misfire check engine light
Tested fuel pump pressure good
Cleaned and soaked fuel injectors
Sea Foamed engine

______

sebbyxtc

iTrader: (7)

Re-tune?

And try 1 step, your not running that much boost for 2 step colder.

sebbyxtc

iTrader: (7)

Unichip or F/ic? By relocated MAF you mean blow thru or....?

davidward

I was using 2 step colder plug but switched to 1 step. It made no difference. Im using Unichip. Been running the same tune for a while. I relocated the Mass air sensor behind the blow off valve so it wouldnt bleed air out of the blow off valve causing it to die.

sebbyxtc

iTrader: (7)

Ok so you have a blow thru set up, umm thats weird. Any leaks? Boost leaks? Maybe try resetting the ecu by disconnecting your battery for like 10 minutes then rry driving it around for like half an hour. What are your AFR's at wide open and cruise? Idle?

davidward

The only problem i have is at idle. full boost im good. = no boost leak . The car is dyno tuned so AFR is perfect at idle and under boost. resetting eco is not going to do anything. I have done that in the past to reset check engine light but now i have the scan computer. I have no idea what you mean by blow thru setup? My blow off valve is vent to atmosphere instead of recycling like it was. that is why i relocated my MAF meter to vent to atmosphere on the turbonetics kit.

sebbyxtc

iTrader: (7)

Post a pic of your current set up, that might help.

creamyxb2

iTrader: (1)

did you check your fuel pressure. what was it at.

davidward

Pressure was normal around 45 50... Now the car runs perfect in boost. Would think if there was a problem with pressure I would notice it when boosting. Not just at idle? I can understand a misfire with low pressure. But then I would really notice it under boost and the afr would be way off instead of a little bit rich. This kidda why I'm puzzled by this. Since I have posted this tread my check engine light hasn't came back on. Only thing I did was change plugs. Unless my car is just that sensitive to spark plugs over time. Car still rev bounces but hasn't died as much and rpm has been normal about 800 to 900 with a/c on.