Cylinder 4 missfire and lean code

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Jul 19, 2009 | 06:36 AM

kink2227

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Cylinder 4 missfire and lean code

I am working on a 1997 mazda b2300 (ranger Clone).. it has the 2.3 SOHC ford engine.. i am getting 2 different codes.. P0304 and P0171 one is cylinder four missfire and the other is System too lean bank 1... I have replace the spark plugs and wires sence they were origanal and should have been done a long time ago... now i am still geting the 2 same codes... i have checked around for any vaccume leaks and to see if anything was disconnected.. but everything looks good.. also the fuel filter has been changed not too long ago so i know thats good.. checked the coil packs and i am geting good spark... any ideas???

Jul 19, 2009 | 07:46 AM

pawpaw

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From: SW Va

Welcome to FTE.

You've been busy on this one & have done some good trouble shooting.

You could have more than one problem.

The way the computer detects a cyl misfire, by expecting a crankshaft rpm for the operating conditions, but measuring a difference from that value, means a misfire code could be spark, fuel, or mechanical(like a sticking or leaking valve, piston rings, ect) based.

So seeing as how you have a 4 banger & also have a lean code for your one bank engine & knowing the above, maybe a fuel injector problem belongs on your suspect list.

How does the O2 sensors PID output to the computer look????
If it's switching is out of range, or slow/lazy & you have more than 100K miles on it, maybe add it to your suspect list.

More info would be helpful, like what year & how many miles on this ride.
Any engine mods & where is it on all past & present due scheduled maintenance items, other than the plugs, wires & fuel filter you've posted????

Did this problem come about suddenly after some event, or slowly over time????
Do you have any other codes, if so post All of them.

More thoughts for pondering, let us know what you find.

Jul 19, 2009 | 08:23 AM

kink2227

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Thanks for the response!! The truck is a 1997 and it has about 192,000 miles on it...all of the normal maintiance has been done on the truck..oil changes every 3k,air and fuel filters changed.. etc.. the problem came one day all of a sudden..it runs really rough up to about 2,500-3,000 rpm.. but still lacks power.. i am thinking about replacing the #4 injector.. i would try and swap it with another one and see if the problem moves but it looks like a big job.. it looks like i am going to have to pull the intake manfold to get the fuel rail up..

Jul 19, 2009 | 08:24 AM

kink2227

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The truck is bone stock no engine mods at all

Jul 19, 2009 | 09:15 AM

Bear River

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From: Salt Lake City, Utah

Misfires can cause lean codes. Solve the misfire and you will probably solve the lean code as well. Since your spark is good, I would agree that you may have a sticking injector.

Jul 19, 2009 | 09:29 AM

pawpaw

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From: SW Va

Well with a lean code & the misfire code & the problem coming about suddenly & the mileage on this ride, right now I want to lean toward a fuel injector problem.

You could use a mechanics stethoscope, or rig one from a length of tubing, broom handel, or long scredriver, to listen to #4 injector, in the trouble rpm range, to determine if you can hear a diference in the sound #4 injector makes, compaired to the others.

What kind of injector cleaning did you do & with what product????

BUT if it could be more than one problem, the other possibilities need to be eliminated too.

So maybe a compression check, or cyl balance check & coil pack voltage output check, or coil pack wet down test should also be considered.

More thoughts for consideration.
Let us know what you find.

Jul 19, 2009 | 10:26 PM

kink2227

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well i went with the injector.. since its what i thought too. if the injector is not spraying then the engine would miss and then the exhaust 02 sensors would pick up on the lean mix.. i had to remove the top part of the intake manifold to get to the fuel rail but its not too bad of a job... i actually think doing the spark plugs was worse..i am going to put the rest of it togeather tomorrow and i will let you know how i make out... thanks again for the help..