95 LT1 Running Lean
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Joined: Nov 2004
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From: Birmingham Alabama
95 LT1 Running Lean
I'm pulling codes 44 and 46 (lean 02 sensor readings), and I can't figure out why? I've had it in the shop several times to no avail. I've replaced the wires and plugs, injectors, MAF sensor, all 02 sensors and a leaky intake manifold gasket. I'm at the end of my rope and need some help. 
Melting Slicks
Joined: Sep 2000
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From: Green Bay WI
Originally Posted by tholm1
I'm pulling codes 44 and 46 (lean 02 sensor readings), and I can't figure out why? I've had it in the shop several times to no avail. I've replaced the wires and plugs, injectors, MAF sensor, all 02 sensors and a leaky intake manifold gasket. I'm at the end of my rope and need some help.
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From: Lahaina Hi
Your stock fuel presure should be at 43.5 psi.
If you lower the presure to 40 that should decrease the band width to the injector and richen the engine.
Increase the presure and the engine should lean out .
Just my 02 worth.
If you lower the presure to 40 that should decrease the band width to the injector and richen the engine.
Increase the presure and the engine should lean out .
Just my 02 worth.
Melting Slicks
Joined: Apr 2003
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From: NS
Originally Posted by REDC4CORVETTE
Your stock fuel presure should be at 43.5 psi.
If you lower the presure to 40 that should decrease the band width to the injector and richen the engine.
Increase the presure and the engine should lean out .
Just my 02 worth.
If you lower the presure to 40 that should decrease the band width to the injector and richen the engine.
Increase the presure and the engine should lean out .
Just my 02 worth.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Originally Posted by REDC4CORVETTE
Your stock fuel presure should be at 43.5 psi.
If you lower the presure to 40 that should decrease the band width to the injector and richen the engine.
Increase the presure and the engine should lean out .
Just my 02 worth.
If you lower the presure to 40 that should decrease the band width to the injector and richen the engine.
Increase the presure and the engine should lean out .
Just my 02 worth.
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 60
From: Fremont Oh
If you lower pressure it will lean out... more fuel pressure will richen it up... trust me on that! At WOT, youe ecm /pcm would compensate in closedloop by adjusting the injectors accordingly.
Yes you should be at 43.5, if not it may be the fuel pump going south...
Mo
Yes you should be at 43.5, if not it may be the fuel pump going south...
Mo
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Safety Car
Joined: Apr 2004
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From: Lahaina Hi
Sorry I know for a fact the presure is 43.5 stock.
I use tuner cats and datamaster when I tune my nitrous ,that is what I do when I change the BLM's to change the fuel pulse width for the set up to turn low 11's at 40 psi.
I use tuner cats and datamaster when I tune my nitrous ,that is what I do when I change the BLM's to change the fuel pulse width for the set up to turn low 11's at 40 psi.
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From: Birmingham Alabama
I checked my fuel pressure. With the key on and the engine off I'm at 44 psi, and with the engine on its at about 36 psi.
So I assume that's not it. Anyone else have any ideas about what would make it run lean. I ran over every inch of vaccum tube I could see and didn't find any cracks. I'm about ready to cry.
So I assume that's not it. Anyone else have any ideas about what would make it run lean. I ran over every inch of vaccum tube I could see and didn't find any cracks. I'm about ready to cry.
Melting Slicks
Joined: Oct 2004
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From: Austin Texas
You have said you are throwing codes to indicate lft O2 sensor and "lean" condition. OK ....but, more importantly,
could you describe how your engine is running? Can you describe how your engine reacts to this "lean" condition? For example, doe's it behave as tho it is fuel starved during acceleration. All you have told us is that you are throwing an error code and replaced a bunch of sensors, but you have not given enough details on how the engine is operating .....
also, what is a code 46? are you sure you didn't mean to say 64???
could you describe how your engine is running? Can you describe how your engine reacts to this "lean" condition? For example, doe's it behave as tho it is fuel starved during acceleration. All you have told us is that you are throwing an error code and replaced a bunch of sensors, but you have not given enough details on how the engine is operating
.....also, what is a code 46? are you sure you didn't mean to say 64???
Last edited by MikeC4; Feb 11, 2005 at 07:12 PM.
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From: Birmingham Alabama
Sorry, I meant code 64, for lean right O2. Basicly the car responds as if its running out of gas when I depress the accelerator pedal. (I've done it once so I know how that feels). So when I hit the gas it is either slow to accelerate or stumples and does nothing. The idle is real rough, so rough that it shakes the car sometimes. What really gets me is that sometimes when I first turn it on it runs ok, but eventually starts to run like crap. The only thing I can think of is that the EGR value is sticking open, but that should throw a code too, maybe? When the check engine light comes it runs better, but still idles rough, lacks power and gets bad gas mileage (6 mpg).
I check the codes by jumping the 4 and 12 pins on the DLC connector (16 pin pre-OBDII) and reading the speedometer.
I check the codes by jumping the 4 and 12 pins on the DLC connector (16 pin pre-OBDII) and reading the speedometer.
Pro
Joined: Feb 2002
Posts: 565
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From: Chandler AZ
Attach the fuel pressure gauge to the valve and tape the gauge head to the windshield so that you can see it while you drive around and see if the pressure drops when you accelerate, or if it stays up. Sounds like it might be a fuel pump on the way out. Mine would work fine sometimes and not at other times. I caught it this way. Good luck, Robert
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From: Birmingham Alabama
Brian,
Sounds like your on to something. I'll try to see what the pressure does during driving. I was thinking about it, and pressure is potential across a resistance, not a flow rate. So when the demand for fuel is low, say idle, the pump can move enough volume of fuel to keep the pressure up, but when the demand is high, a failling pump can not generate enough flow of fuel to build up pressure to 44 (or around 36 psi with vacuum). I know the pressure regulator is fine, I hope it's the fuel pump so I can get this thing fixed.
This is all so fustrating ...I like working on my MGB better, everything is simple mechanical systems, no computers and solid state electronics.
Sounds like your on to something. I'll try to see what the pressure does during driving. I was thinking about it, and pressure is potential across a resistance, not a flow rate. So when the demand for fuel is low, say idle, the pump can move enough volume of fuel to keep the pressure up, but when the demand is high, a failling pump can not generate enough flow of fuel to build up pressure to 44 (or around 36 psi with vacuum). I know the pressure regulator is fine, I hope it's the fuel pump so I can get this thing fixed.
This is all so fustrating ...I like working on my MGB better, everything is simple mechanical systems, no computers and solid state electronics.
Melting Slicks
Joined: Dec 2000
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From: Fremont Oh
If it happens to be the fuel pump actually the swap is not all that difficult, I changed mine out for a higher flowing pump in about an hour... they was refabing the mounting bracket...
Mo
Mo
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From: Birmingham Alabama
I finally got around to changing out the fuel pump. It did nothing! I'm still throwing codes 44 and 46 (lean O2s). It idles irradicly and once the car heats up it starts to stumble on acceleration until the check engine light comes on. Whatever the computer changes it makes it drivable, but it doesn't have the power it should and gets terrible gas mileage (6mpg).
I'm so fustrated Does anyone have any ideas. Could it be the MAP sensor?
I'm so fustrated
Does anyone have any ideas. Could it be the MAP sensor?
Melting Slicks
Joined: Oct 2004
Posts: 2,510
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From: Austin Texas
Originally Posted by tholm1
I finally got around to changing out the fuel pump. It did nothing! I'm still throwing codes 44 and 46 (lean O2s). It idles irradicly and once the car heats up it starts to stumble on acceleration until the check engine light comes on. Whatever the computer changes it makes it drivable, but it doesn't have the power it should and gets terrible gas mileage (6mpg).
I'm so fustrated Does anyone have any ideas. Could it be the MAP sensor?
I'm so fustrated
Does anyone have any ideas. Could it be the MAP sensor?You may want to check your EGR valve to be sure it is not stuck in open position, which would always circulate some exhaust back into the Intake...EGR's can really screw things up if they are broke..
When your SES light comes on, and then the car becomes drivable, that is when the ECM/PCM ignores the O2 sensors, and refers to a lookup table for AFR.
How many miles on car?
Last edited by MikeC4; Feb 27, 2005 at 08:38 PM.