3800 Rich Misfire? Need opinions with the car

[Bru]

I'm getting a random shuddering/misfire during boost that seems to be triggered during aggressive throttle stabs. If I gradually ease into the throttle it runs pretty strong, but if I'm cruising at 40 mph and stomp on it, the car will fall on its face.

I know looking at the narrowband isn't the best way to check a/f, but it's all I've got now. Looks like I'm running pretty rich with 02s sometimes in the 950-960 range at WOT, so is this enough to cause a rich misfire? Sometimes it will run at WOT without the shudder, other times it will fall on its face. When I pulled the plugs on Sunday there was fuel around the base of the plugs but the plugs looked good otherwise.

I'm going to check the wires tomorrow -- well, I guess today -- and maybe throw a new set of plugs/wires in there. 1.9 Rockers, 90# springs, alt rewire and caspers fuel pump rewire just went on the car as well.

I don't think I'm going to run the car on Sunday unless I can get this figured out.

The first scan is with the occurrence, the second scan is without. It would be nice if all I need is a tune, but just wanted to throw this out there. Thanks.

http://scandepot.net/viewscan.php?pk=5495

http://scandepot.net/viewscan.php?pk=5496

Click to read more...

 

[PANDA]

Your getting some pretty hefty KR for your mods. kinda like my car

Honestly, I think at your mod level, a custom tune is needed. From looking at the scan the first thing I see is the LTFT's locking in at ~9. (Thats pretty bad) You want to get the trims at idle, part throttle, cruise, WOT as close to zero as possible.

 

[Bru]

Yes, I realize that, but I'm wondering if the rich condition could be causing this misfire I'm experiencing.

 

[BLOWN GP]

Your getting some pretty hefty KR for your mods. kinda like my car

Honestly, I think at your mod level, a custom tune is needed. From looking at the scan the first thing I see is the LTFT's locking in at ~9. (Thats pretty bad) You want to get the trims at idle, part throttle, cruise, WOT as close to zero as possible.

X2

 

[PANDA]

Yes, I realize that, but I'm wondering if the rich condition could be causing this misfire I'm experiencing.

Im not sure, I would also would like to know many how rich your car has to run for it to effect knock.

Blowngp, I just realized u got like the exact same mods as bruGTP. sit heads!

 

[Bru]

I don't think running rich would cause KR, but a rich misfire is a possibility.

 

[Bru]

Bump for night crew.

 

[02BlueGT]

If it is rich enough for the plugs to be wet then it def could cause a miss, how smooth is the idle..... Remember liquid fuel doesn't burn, so too much and it won't ignite

 

[Bru]

Idle is pretty smooth. A blip here and there, but it did that blip long before this problem popped up.

I've got new wires, plugs and belts I'm going to slap on here in a little while. I'm letting the car cool down right now.

 

[02BlueGT]

If doing the plugs on a hot motor, the rear exhaust manifold cools off way before the front

 

[RebelGTP]

If doing the plugs on a hot motor, the rear exhaust manifold cools off way before the front

rly:

Changed mine today...

 

[Bru]

*Fixed

 

[10sec]

plugs fouled out and causing spark blowout? (as in was that the problem?)

 

[Bru]

Per usual, Mr Ron V guessed it right off the bat. Plug wires were shot. I took them off and ohm'd them out, and many were showing much higher resistance than the new ones. Plugs looked pretty good but I threw a fresh set in there just in case.

The wires were new at the beginning of the summer but have been on/off the car a few times for miscellaneous mods and check-ups, and I guess they don't like to be fiddled with, even when newer.