Lean Misfire
04-29-2011, 08:58 PM
#1
Lean Misfire Hey guys, it's been a while since I've had to post in this section but I guess my luck ran out.
Car:
2001 Trans Am WS6
Vengeance Racing VRX5 Cam and all the goodies
Ford 42lb injectors
Full Bolt Ons
MSD wires
Yank 4000 Stall
Built Tranny
Moser 9"
Blah blah
Tuned in Speed Density, Open Loop
Basically it goes like this, car has run fine since all of these modifications so I know it doesn't have anything to do with the addition of new parts. The car didn't get driven much over the winter, but did get started and run several times. Noticed a slight misfire a few months ago and suspected the VATS system was getting screwy with the BCM, so I tuned out the VATS. This didn't help any, however switching to one of my spare keys did. I believe this to be a coincidence but I figured I'd mention it anyway. Ran fine the last time I drove it before winter.
Fast forward to the next time I try to drive it. This time it misses pretty badly under throttle or load, and while doing so I can watch my Wideband spike WAY lean. I suspected the stock fuel pump had begun to **** the bed, so I picked up a Racetronix unit knowing that regardless it would be a worthwhile upgrade. The pump did no good whatsoever, nor did a fuel filter.
At this point my lsx buddies have suggested the possibilities of bad injector, bad coil, bad plug wire, and insufficient voltage to the fuel pump. The car hasn't thrown any codes, however being tuned in open loop doesn't allow it to monitor fueling to know if its running lean. Codes are being monitored via Aeroforce Interceptor gauges which also show no misfires or knock retard.
Does anyone have any ideas, tips or suggestions to diagnosing this? I understand that logging real-time and historical misfires by cylinder in HPtuners would be very beneficial, however I wont be able to do so until sunday at the earlier and wanted to gather some opinions in the mean time.
Thanks a bunch!
Car:
2001 Trans Am WS6
Vengeance Racing VRX5 Cam and all the goodies
Ford 42lb injectors
Full Bolt Ons
MSD wires
Yank 4000 Stall
Built Tranny
Moser 9"
Blah blah
Tuned in Speed Density, Open Loop
Basically it goes like this, car has run fine since all of these modifications so I know it doesn't have anything to do with the addition of new parts. The car didn't get driven much over the winter, but did get started and run several times. Noticed a slight misfire a few months ago and suspected the VATS system was getting screwy with the BCM, so I tuned out the VATS. This didn't help any, however switching to one of my spare keys did. I believe this to be a coincidence but I figured I'd mention it anyway. Ran fine the last time I drove it before winter.
Fast forward to the next time I try to drive it. This time it misses pretty badly under throttle or load, and while doing so I can watch my Wideband spike WAY lean. I suspected the stock fuel pump had begun to **** the bed, so I picked up a Racetronix unit knowing that regardless it would be a worthwhile upgrade. The pump did no good whatsoever, nor did a fuel filter.
At this point my lsx buddies have suggested the possibilities of bad injector, bad coil, bad plug wire, and insufficient voltage to the fuel pump. The car hasn't thrown any codes, however being tuned in open loop doesn't allow it to monitor fueling to know if its running lean. Codes are being monitored via Aeroforce Interceptor gauges which also show no misfires or knock retard.
Does anyone have any ideas, tips or suggestions to diagnosing this? I understand that logging real-time and historical misfires by cylinder in HPtuners would be very beneficial, however I wont be able to do so until sunday at the earlier and wanted to gather some opinions in the mean time.
Thanks a bunch!
05-01-2011, 05:58 PM
#3
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6 Posts
Why can't you monitor O2 voltages? They should still
be active. Look for a discrepancy bank-bank.
Seen recently somebody chased down single cylinder
misfiring with a thermal gun on the exhaust primaries.
Don't know whay your Interceptor will do, if you are
looking to chase a misfire you want Misfire Current
Cylinder Mode, 1...8. But these can sometimes be
off (real misfiring cyl may not be the one reported)
I have heard. The temp gun doesn't lie so much.
Have you pulled plugs looking for signs of ill running,
or simply crust?
be active. Look for a discrepancy bank-bank.
Seen recently somebody chased down single cylinder
misfiring with a thermal gun on the exhaust primaries.
Don't know whay your Interceptor will do, if you are
looking to chase a misfire you want Misfire Current
Cylinder Mode, 1...8. But these can sometimes be
off (real misfiring cyl may not be the one reported)
I have heard. The temp gun doesn't lie so much.
Have you pulled plugs looking for signs of ill running,
or simply crust?
05-03-2011, 05:20 PM
#5
Logging revealed no outstanding data. Drained fuel lines and pumped the tank dry, refilled with brand new gas and it runs like a top. Now I have a brand new racetronix pump that i didnt need, oh well!!!
Moral of this story: Don't rule out the basics!
Moral of this story: Don't rule out the basics!
