misfire at 6300-6500rpms

[gdc5ind]

Ok. I have a 1jz-gte twin with 3.25"downpipe and walbro fuel pump. It seems that after i upgraded my exhaust ( 3.25" downpipe to duel 3" straight through mufflers) my car has started to misfire, this only happens at 6300-6500 rpms. I recently changed my turbos because i was getting heavy smoke when i let off the gas after running the car under load, not when in neutral revving. After i changed the turbos with used turbos it stopped smoking and misfiring, but after a few weeks on the new turbos it began to smoke again, and misfire. today i pulled all my spark plugs and coils and found hairline cracks on my coils, and all the connecting ignition clips have hardened and become bridal. To fix this problem i bought new ignition clips soldered them on and put large shrink wrap around the legs of the coils. After doing this my problem persists. here is a video of my car misfiring, and another puzzle peace is that this misfire seems to come on sooner if i just hit WOT early and don't let the boost build and roll into the gas.http://s533.photobucket.com/albums/ee337/gdc5ind/?action=view&current=MVI_2201.flv

 

[JASONA70]

your video doesn't work.. at least not for me.


whats the status of your plugs?? timing?

 

[suprahero]

I haven't checked the video yet, but my car does this when my plugs are gapped to big. I now run a .022 gap on NGK 6097's. You won't have to run this small a gap, but you may want to try .028 or even .025 and see if it helps you.

Do you have a wideband to show if you're running lean at those rpms? It will misfire and sputter if it's running out of fuel also.

 

[gdc5ind]

That seems to be what is most likely, according to the forums. I will check my timing and my gaps. lol

Thanks

 

[tissimo]

Video doesn't work, I'm going to say fuel cut though.

If its the plugs/coils You'd have the missfire around peak torque (peak cyl pressure, hardest to spark) and unless you have major boost creep it wouldn't be 6k+.

 

[gdc5ind]

check the clip again.

 

[Jostar]

I haven't checked the video yet, but my car does this when my plugs are gapped to big. I now run a .022 gap on NGK 6097's. You won't have to run this small a gap, but you may want to try .028 or even .025 and see if it helps you.

Do you have a wideband to show if you're running lean at those rpms? It will misfire and sputter if it's running out of fuel also.

I concur DR.... Check the gap & try & get a wideband to see if it leans out, Did you swap the stock fuel pump outta the SC300??? if no then that right there could be the problem....

 

[gdc5ind]

well i checked all the plugs they were all .030. My setup is a soarer 1jz-gte stock with a auto ecu. i swaped a r154 ,walbro, 3.25"downpipe, duel 3" straight through mufflers. I extended the wire harness myself, maybe the knock sensor is getting outside interruption?

 

[Jostar]

well i checked all the plugs they were all .030. My setup is a soarer 1jz-gte stock with a auto ecu. i swaped a r154 ,walbro, 3.25"downpipe, duel 3" straight through mufflers. I extended the wire harness myself, maybe the knock sensor is getting outside interruption?

There is a great possibility that the knock sensors are going crazy due to not being properly shielded, why did you extend the harness?? i have read that it reaches enough in the cabin & all you have to extend are dash plugs...

 

[tissimo]

Did you try gapping down the plugs when you checked em?

Knock sensors wouldn't cause a mis.

 

[gdc5ind]

Did you try gapping down the plugs when you checked em?

Knock sensors wouldn't cause a mis.

No i didnt. do you think that will help?

 

[tissimo]

No i didnt. do you think that will help?

worth a shot, its free.. only takes a few minutes.

 

[suprahero]

I'm pretty sure someone suggested this earlier...........:sarcasm:

 

[gdc5ind]

I'm pretty sure someone suggested this earlier...........:sarcasm:

funny guy.......