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Bret
Dodge Dakota
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3/15/2005
15:43:56
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 Subject: Running Lean
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The light gray plug color tells me that my 5.9 is running lean. I have done these mods (2002 QC 4X4):
Gibson headers & Magnaflow muffler
Stock intake with runners cut & ported TB
Harland-Sharp 1.7RR
High-flow K&N
MSD6A
TPS mod
180 stat
Autolite 3922s (2 heat ranges colder than stock)
Hypertech Power Programmer III
Should I install larger injectors (maybe 21#?) to richen the mixture, or is there something else going on?
Thanks.
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Crow318
Dodge Dakota
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3/15/2005
16:03:07
|  RE: Running Lean
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I just ran into an issue where I assumed someone didnt know much, so I want to prequalify this by saying these are just ideas, and if they don't apply, I appoligize.
Are all the plugs the same color?
A picture in this case would let the rest of us know exactly the color that you describe. But a light grey is nothing that would alarm me, unless there was some other indication that you were lean, a check engine light with a code perhaps.
You may have part of that system overriden based on the mods that you have. But if not, the computer should let you know if a lean situation occurs and the computer can not compensate for. An o2 sensor is unaffected by all of those mods. It helps the computer adjust. If it says lean, the computer will add fuel. If you exceded the range in the compuer, it will let you know. In that case a larger injector would probably be in order.
Another thing to look at is the heat of your spark. Even with a cooler plug, a really strong coil can make an accurate plug read difficult.
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Bret
Dodge Dakota
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3/15/2005
16:35:13
| RE: Running Lean
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Message:
Crow318
Thanks for the reply.
The plugs are all the same color and it's actually more of a whitish gray. I am alarmed because, before I did any of the mods the stock plugs where showing dark/very dark gray. I really started to notice it after the intake/TB/Roller rocker mods.
As far as the spark I am running the stock coil with the MSD.
To get even more confused, I just installed an air/fuel gauge expecting to see the mix showing lean, but it is not. The gauge is hanging around the rich end of the stoich range, then bounces lean and back again. Nice LED light show, but I was hoping to get some more diganostic value out of it.
If the PCM is adding more fuel to compensate, it doesn't seem to be adding enough.
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Crow318
Dodge Dakota
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3/16/2005
09:00:57
| RE: Running Lean
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Most of the time, a factory tune will make a vehicle run a little rich. They do that to make the vehicles more reliable. Lean will hurt an engine alot faster than rich. That is most likely the reason for the dark plugs to start with.
The new lighter color may just mean that you are closer to the mixture you want. If its lean, you will also notice a decrease in power, and in severe cases, you cant get to highway speeds.
If you installed the gauge right to the o2 sensor that the truck uses, that reading is what the computer sees. The computer filters out those spikes, and averages the readings to get a fuel signal.
That being said, you could have a faulty 02 sensor. I am not sure what they do when they go bad. Most people say that their mileage goes to crap wich would make me think a failure reads lean, and the computer dumps more fuel.
All of the mods you listed help airflow in, so you may be coming up a little short in the fuel department.
I am not sure that all of this really helps you any more. But if you are still thinking lean, you can go up an injector size like you mentioned, and that should take care of your worries.
If nothing else, a good set of matched injectors will help performance a little, and it should also help milage.
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T-racy
Dodge Dakota
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3/16/2005
23:49:29
| RE: Running Lean
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Bret how does it run? Does it run as strong as you think it should? What are your 1/4 mile times? My 93 318 plugs looked the way you described but it ran real good and got decent mileage and I had alot of the same mods as yours. It ran 14.50's at 94 mph and got 17 mpg.
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keen
Dodge Dakota
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3/17/2005
09:26:45
| RE: Running Lean
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Basing your assumption that you have a lean running condtion on plug coloration alone is probably inconclusive. A/F ratios are best measured w/ a wide band 02 sensor as such found on engine dyno's. The factory 02 sensor coupled w/ an a/f gauge leaves a lot to be desired - inaccurate. Most factory PCM's can handle low rpm fuel stradegy, hi rpm fuel control (open loop) may require additional fuel on heavily modified engines. Your engine is basically stock.
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Bret
Dodge Dakota
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3/17/2005
12:58:52
| RE: Running Lean
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Message:
Thanks for the help guys, sounds like the air/fuel is OK. The Dak is a daily driver and runs good enough for a street 4X4, although I'll never forget the night a 6.0L Silverado 2500 passed me on U.S. 340 -- the 5.9 just didn't have the top end!!
I'm getting a custom Y-pipe and 3" exhaust put on in a few weeks and maybe some nawz after that. Just wanted to make sure the A/F was OK.
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