Left Bank Rich, Right Bank Lean? Why?
09-21-2008, 01:32 AM
#1
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Left Bank Rich, Right Bank Lean? Why?
Can't seem to figure it out, put on a new tune, got the car running pretty darn good, but for some reason the left bank is running rich, and the right bank is running lean.. I thought maybe it was just the 02 sensors, or maybe the size of my exhaust but when I pull the plugs match the pcm readings..
Thoughts? Suggestions? Why would this happen? Problem with Rails? Injectors? Fuel pressure is good.
Thoughts? Suggestions? Why would this happen? Problem with Rails? Injectors? Fuel pressure is good.
09-21-2008, 07:57 AM
#2
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Do you have more information? Was everything perfect until the new tune? Has it always been this way? If you could provide cam information, that may help as you commonly see bank differences with large cams.
With a few more pieces of the puzzle, we can help. I had the same issue and resolved it but not sure if yours is exactly my issue.
With a few more pieces of the puzzle, we can help. I had the same issue and resolved it but not sure if yours is exactly my issue.
09-21-2008, 11:51 AM
#3
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Do you have more information? Was everything perfect until the new tune? Has it always been this way? If you could provide cam information, that may help as you commonly see bank differences with large cams.
With a few more pieces of the puzzle, we can help. I had the same issue and resolved it but not sure if yours is exactly my issue.
With a few more pieces of the puzzle, we can help. I had the same issue and resolved it but not sure if yours is exactly my issue.
This is the second time I've been able to get it running on a scanner.. The first time with a proper fresh correct bin file, with the correct definition, but the last time I had it hooked up it did the same. So as far as I know yes. Basically though we might as well consider it a new motor as I don't have any history on it from the prior owner.
Cam: I do not know the cam specs, and the PCM isn't tuned for it.. All I know is that it is a "Blower Cam" that is a slightly smaller then a LT4 Hot Cam (according to the previous owner), the motor came out of a super charged car.
Injectors: Stock
Fuel System: Aeromotive, M1000, PSI 45 Drops to 40 and holds when floored.
Rails: Welded on AN fittings (for some reason my rails are longer then my intake.. See (old photo) http://www.pbase.com/brahm/image/63244921
Ignition: MSD Digital 7 Plus, w HVAC Coil.
Opti: Replaced New Last year same with wires.
Plugs: NGK Replaced with OPTI (please note car has maybe 600 miles since opti/plug replacement i didn't drive it much)
Heads / Intake : Stock supposedly cleaned up/port matched a little I haven't taken the intake off to see.
Headers: (way to big for this motor) Hooker Pro Comps 2" or 1 7/8th
Exhaust: (Waaay to big for this motor) 3.5" Straight pipes w/flowmaster dumps (need to fix this or get a blower lol)
O2 Sensors: Recently replaced and appear to be working correctly when scanning.
Trans 4l60e
TB: 58mm BBK
Intake Pipe: Vortech elbow w/a Cone filter on the end
Maf: Stock..
Pistons: Forged, slightly less compression then stock actual compression unknown
Motor Displacment: 355.
Rockers: Crane Golds.
Hmm.. I think thats everything.. Let me know if there is something specific you need to know that I didn't think off.
Thanks again
-Brahm
09-21-2008, 01:02 PM
#4
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What do othe BLM's look like when you do the scan? What cells have the "split" BLM's?
To make sure we understand what you said about one bank rich and one bank lean - when you checked the plugs, you found one bank with carbon (rich) and the other bank with bluish/burnt electrodes, a white apprearance, and spotty deposits on the insulator (lean)? Is this correct?
The fuel rails in the photo appear to be stock 93 rails on a stock 93 intake manifold.
To make sure we understand what you said about one bank rich and one bank lean - when you checked the plugs, you found one bank with carbon (rich) and the other bank with bluish/burnt electrodes, a white apprearance, and spotty deposits on the insulator (lean)? Is this correct?
The fuel rails in the photo appear to be stock 93 rails on a stock 93 intake manifold.
09-21-2008, 03:53 PM
#5
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Not really sure what BLMs are, I know there were this 2 numbers my buddy said should be around 128, and one side was 128, the other was like 134 or something? Basically, with the program we were using it will read left side, or right side.. and on the left side it was rich (all red instead of white), and on the right side it was lean (all green instead of white) when I pulled the plugs the right side plugs were whitish. Didn't' look for spotty deposits.
09-22-2008, 05:34 AM
#6
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Your buddy is correct. BLM's (forgot what the abbreviation is for) of 128/134 is acceptable at idle and just off idle with an aftermarket cam.
What scanner you using? If DataMaster, the "cell", as Injuneer pointed out, is just below the BLM readings. This is important to know.
Do a search for split BLM's and you will get lots of info.
FYI, I have a split similar to your at idle and just off idle and I have put MANY hours into getting it close but look at the size of my cam. My car runs fantastic so don't sweat it too much. After about 1/2 throttle, my car does not have this issue anymore. If you are off this much at WOT, then we have problems. Until proven, I think you are fine. Fine tune if you want but it will take some learning to get perfect and not sure the time you want to put into tuning. I love it so I put in the time but some don't. Personally, with a custom setup that you have, I would put in the time.
What scanner you using? If DataMaster, the "cell", as Injuneer pointed out, is just below the BLM readings. This is important to know.
Do a search for split BLM's and you will get lots of info.
FYI, I have a split similar to your at idle and just off idle and I have put MANY hours into getting it close but look at the size of my cam. My car runs fantastic so don't sweat it too much. After about 1/2 throttle, my car does not have this issue anymore. If you are off this much at WOT, then we have problems. Until proven, I think you are fine. Fine tune if you want but it will take some learning to get perfect and not sure the time you want to put into tuning. I love it so I put in the time but some don't. Personally, with a custom setup that you have, I would put in the time.
09-22-2008, 10:59 AM
#7
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Your buddy is correct. BLM's (forgot what the abbreviation is for) of 128/134 is acceptable at idle and just off idle with an aftermarket cam.
What scanner you using? If DataMaster, the "cell", as Injuneer pointed out, is just below the BLM readings. This is important to know.
Do a search for split BLM's and you will get lots of info.
FYI, I have a split similar to your at idle and just off idle and I have put MANY hours into getting it close but look at the size of my cam. My car runs fantastic so don't sweat it too much. After about 1/2 throttle, my car does not have this issue anymore. If you are off this much at WOT, then we have problems. Until proven, I think you are fine. Fine tune if you want but it will take some learning to get perfect and not sure the time you want to put into tuning. I love it so I put in the time but some don't. Personally, with a custom setup that you have, I would put in the time.
What scanner you using? If DataMaster, the "cell", as Injuneer pointed out, is just below the BLM readings. This is important to know.
Do a search for split BLM's and you will get lots of info.
FYI, I have a split similar to your at idle and just off idle and I have put MANY hours into getting it close but look at the size of my cam. My car runs fantastic so don't sweat it too much. After about 1/2 throttle, my car does not have this issue anymore. If you are off this much at WOT, then we have problems. Until proven, I think you are fine. Fine tune if you want but it will take some learning to get perfect and not sure the time you want to put into tuning. I love it so I put in the time but some don't. Personally, with a custom setup that you have, I would put in the time.
09-22-2008, 07:45 PM
#8
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Could the fact that I'm using a 93 intake, motor ect.. with a 94 Opti Computer, trans have anything to do with it? Ie Batch-fire vs sequential? (don't know much about this) wanted to throw that out there.
09-26-2008, 08:10 AM
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A very slight misfire or a small leak in the exhaust system before the O2 sensors can cuase the kind of minor BLM elevation that you are seeing. Or even one injector that is flowing different than the others. One O2 sensor could be "off" by that much. One valve could be adjusted too tight.
Before you start changing things via programming, find out what is causing the problem, and rule out as many of the above causes as you can.
Try swapping the O2 sensors side to side, and see if the 134 BLM follows the sensor. Then do the same thing with the injectors - swap the right bank for the left bank. If the 134 BLM follows the injectors, you've found the problem.
The 93 fuel rails are designed for batch-fire, and the crossover is different than the sequential fire rails. Whether that's enough to cause a minor imbalance in fuel flow is unclear.
Before you start changing things via programming, find out what is causing the problem, and rule out as many of the above causes as you can.
Try swapping the O2 sensors side to side, and see if the 134 BLM follows the sensor. Then do the same thing with the injectors - swap the right bank for the left bank. If the 134 BLM follows the injectors, you've found the problem.
The 93 fuel rails are designed for batch-fire, and the crossover is different than the sequential fire rails. Whether that's enough to cause a minor imbalance in fuel flow is unclear.
09-28-2008, 08:10 PM
#12
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Yes, 93 w/94 (the guy i got it from didn't want to have to flash eproms or something so he upgraded the computer).. The 02s are replacements I bought BOSCH or something, for a 94 camaro. (4 pin in line), and yes we checked the sides are correct.
09-28-2008, 08:12 PM
#13
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Join Date: Jul 2008
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A very slight misfire or a small leak in the exhaust system before the O2 sensors can cuase the kind of minor BLM elevation that you are seeing. Or even one injector that is flowing different than the others. One O2 sensor could be "off" by that much. One valve could be adjusted too tight.
Before you start changing things via programming, find out what is causing the problem, and rule out as many of the above causes as you can.
Try swapping the O2 sensors side to side, and see if the 134 BLM follows the sensor. Then do the same thing with the injectors - swap the right bank for the left bank. If the 134 BLM follows the injectors, you've found the problem.
The 93 fuel rails are designed for batch-fire, and the crossover is different than the sequential fire rails. Whether that's enough to cause a minor imbalance in fuel flow is unclear.
Before you start changing things via programming, find out what is causing the problem, and rule out as many of the above causes as you can.
Try swapping the O2 sensors side to side, and see if the 134 BLM follows the sensor. Then do the same thing with the injectors - swap the right bank for the left bank. If the 134 BLM follows the injectors, you've found the problem.
The 93 fuel rails are designed for batch-fire, and the crossover is different than the sequential fire rails. Whether that's enough to cause a minor imbalance in fuel flow is unclear.
As far as fuel rails, intake.. not sure what to do there.. I guess I can wait until I get an aftermarket intake & heads.. although I'd hate to slap some more performance gear before solving my current problems.
09-30-2008, 02:24 AM
#14
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Thanks I can't switch o2s but I just replaced them.. (they are different length and won't swap sides) I'll try swapping the injectors. I would think though (and please correct me if i'm wrong) If the issue was just an incorrect injector reading, the plugs would still read correctly?
As far as fuel rails, intake.. not sure what to do there.. I guess I can wait until I get an aftermarket intake & heads.. although I'd hate to slap some more performance gear before solving my current problems.
As far as fuel rails, intake.. not sure what to do there.. I guess I can wait until I get an aftermarket intake & heads.. although I'd hate to slap some more performance gear before solving my current problems.
09-30-2008, 03:40 PM
#15
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