Lean running Roadmaster - Chevy Impala Forums
Buick Roadmaster General and Technical discussion for the B-Body Buick Roadmaster (1991-1996) and Oldsmobile Custom Cruiser (1991-1992).

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post #1 of (permalink) Old 05-10-2011 Thread Starter
jtg
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Unhappy Lean running Roadmaster

I am a new member, hope I can get some help. I have a 1996 Roadmaster sedan with the 5.7 LT1 motor. The computer code shows lean in left and right bank. This problem showed up rather suddenly. It ran fine, then I had difficulty starting it after it was not run for several days.

Once I get it running, it is obviously lean if I try to accelerate for a few minutes, then it seems to run OK.

If it were the fuel filter or fuel pump, it seems it would not get better after a few minutes of running.

I would appreciate any ideas. Thanks, jtg
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post #2 of (permalink) Old 05-11-2011
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How does it run when you are driving it?
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post #3 of (permalink) Old 05-11-2011
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Check your fuel pressure and see where its at. If its under 40psi then you may have a slight problem.
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post #4 of (permalink) Old 05-11-2011 Thread Starter
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Lean running Roadmaster

It seems to run OK after a few minutes, even when I floor the throttle and it downshifts. Before it warms up a little, it will pop, since it is lean. Is there any kind of device on it that increases fuel flow when cold? I have not checked fuel pressure yet.

Thanks, jtg
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post #5 of (permalink) Old 05-11-2011
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Naw. An ajustable fuel regulator could do it, but you dont need it. Maybe one of your O2 sensor are out and sending wrong messege to pcm. That can make the car run lean or rich.
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post #6 of (permalink) Old 05-20-2011
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Any time there is an issue like this, check the fuel pressure. It would have saved me a tone of work when I had an issue like this. I normally change the fuel filter for the hell of it, when an issue like this happens. It's only a good thing to change that filter, as it is often forgotten.

My first RMS was goofy. Some days it seemed fine, other days is ran like crap. Sometimes in the same few minutes it would change from fine, to running like crap.

Adjustable fuel pressure regulators only true place is on a forced induction car. Or a car using injectors that are maxed out, and you need more out of them. Either way, using one requires a custom tune. The LT1 PCM is very smart. Try to trick it by adjusting the fuel pressure, and it will figure it out. It will figure it out, and make an adjustment. Like guys who were pulling the fuel PSI on stock tunes, to have it run leaner, and make more power. Within a week or so, the PCM figured it out, and was back where it had been before the change.

You want to use one as a bandaid, because you are too lazy to look for the real issue. Really?? Find the sensor, or wire, or item that was causing it, and you won't need any special parts. Might take some time to trouble shoot, but there are not many sensors, and they are all easy to check. Most can be done with a volt meter, and a pair of safety pins.

~Cory Magner "My name is Cory, and I'm an addict."


95 DCM Buick RMS 14.21 @ 91.79 "Jesus" Blown Engine at 85k
95 DCM Buick RMS 13.52 @ 99.33 "The Doctor" Blown Engine at 180k
96 DGGM Buick RMW. 263k, still on the factory tranny.

And 5 other LT1 powered land yachts Is there Rehab for this Sh*t?
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post #7 of (permalink) Old 11-07-2012
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Lean on both banks

My '96 Roadmaster had the check engine light on for a couple of years with a code that indicated lean on both banks. Seemed to run OK, although the gas mileage was down a bit. I recently discovered the problem when I heard a very slight hissing noise near the engine cover: The short rubber elbow right at the PCV valve (left side of the engine) was clogged up AND had a hole in it. Problem solved!!
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post #8 of (permalink) Old 11-07-2012
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Lean

Duke may have the answer, and that would be great, however if it is not, Mr Buick's suggestion is one I always tell people. On fuel injected vehicles or Harleys ( ex master tech ) low pressure can act like so many things. Low power, stumbling, act like you have an ignition problem etc. Your car should run a little rich when first starting up and then as it warms to temp it will reduce the AF ratio accordingly.

Jeff
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