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626 Code P0171 - System Too Lean (Bank 1)

Old 12-17-2007, 01:50 PM
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Join Date: Sep 2007
Posts: 12
Default 626 Code P0171 - System Too Lean (Bank 1)

After my continuing search for ignition problems seemingly solved, I just got a new check engine light.
I've searched the forum on this and see some remarks concerning vacuum connections as well as MAF.
I cleaned the MAF not that long ago and in reality it did not appear dirty at all before cleaning.
I am not sure how this code would translate into an MAF problem indication.
But the lean running indication could explain something on the occasional rough idle or stumbling on acceleration.
Any good tips on a troubleshooting tree for this?
Old 12-19-2007, 12:02 PM
Join Date: Jul 2006
Posts: 11
Default RE: 626 Code P0171 - System Too Lean (Bank 1)

check for air leaks, is everything sealed as it should be?
Old 12-19-2007, 01:27 PM
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Posts: 12
Default RE: 626 Code P0171 - System Too Lean (Bank 1)

As soon as time permits, I plan to examine all areas in air flow and vacuum for weak connections, leaks, etc. Hopefully I will find something suspect.
Old 12-20-2007, 09:09 AM
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Default RE: 626 Code P0171 - System Too Lean (Bank 1)

Update - confusing. Last night the CEL went back off on its own - second time it did this with Code P0171. So at the moment I still don't know why it went on let alone why it went back off. It's like having a symptom that leads you to believe you are sick, you go to see the doc and there's nothing to examine or test for.
Old 12-30-2007, 03:32 PM
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Default RE: 626 Code P0171 - System Too Lean (Bank 1) AND P0303 Misfire

The P0303 just happened today 12/30/07.
After doing a lot of review of similar problems starting with the original P0171 too lean:
1. I have examined all the vacuum hoses and connections without finding anything.
2. Some others in the forum and other forums have encountered P0171 as the result of a leaking intake manifold gasket, which also can contribute to rough running at idle.

I was planning on changing the gasket in a few days and now I have the cylinder 3 misfire.

Would anyone think that if the intake gasket has broken down on cylinder 3 area, it could eventually deteriorate into a misfire condition? others have experienced, could the misfire be the result of a coil pack breakdown and have no direct relationship to the P0171 issue?

Old 01-04-2008, 11:53 AM
Join Date: Sep 2007
Posts: 8
Default RE: 626 Code P0171 - System Too Lean (Bank 1)

On cleaning the MAF... make you cleaned the two tiny sensors (each 1/8" long) that are burried up in the channel tube. They are what need to be cleaned. I used some old freon TF solvent I had saved and a Q-tip (very carefully).
Old 01-13-2008, 10:21 PM
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Join Date: Sep 2007
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Default RE: 626 Code P0171 - System Too Lean (Bank 1)

Hallelujah...the car is running again. After replacing intake manifold gasket. I went through a lot of troubleshooting tests on sensors. The lean problem gave me an idea to check fuel pressure....after going crazy seeing no pressure with ignition ON - BIG thanks to an earlier thread comment from babyhuey that some models pressurize on crank, not ON. No thanks to my crappy Haynes manual that seemed to say otherwise...the only clue was in some specifications indicating only Probe models with the Mazda engine had pressure specs for ON, but not my model Mazda that was crank spec pressures only.
When first trying to start up, the engine just flooded - could have been low pressures and the engine acting like a suction when the injectors opened initially pulling in dribbly non-atomized fuel.
Since the car has 72K and I got it when 1 year old in 2001, I decided to change the fuel filter. I went ahead and put in a new set of plain old NGK resistor plugs andreplaced some Boschplug wires about 4 years old. After reconnecting the fuel lines I decided to make sure the fuel rail was pressurized by cranking the engine several times with no spark plugs installed. Soon after I saw good puffs of vapors coming from all cylinders. I let things dry out and put in the plugs, hooked up the new wires and voila - she's a running. I mean good - smooth idle, no more drop-outs, no more stumbling on acceleration. Before all of this, if I pulled the rear window switches simultaneously with the windows already closed, the rpm's would drop to 500 and then back up. Now....the rpm's don't even blink - stays steady. Life is good.
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