Running lean, scratching head.

[YungICY]

So according to my narrowband air fuel ratio guage my 85 2.3 has been running lean for the past couple months. Its still running strong but definitely not to its full potential. I've been trying to sort out the issue for a while now with no luck.



Timing is good.

Plugs and wires good.

O2 sensor is new.

Both fuel pumps are no older than 6 months.

Fuel filter no older than 8 months.

Fuel pressure good.

Can't say for sure on the injectors but I don't suspect them.

Same issue with two separate ECCs.



I think my issue is coming from fuel delivery. I'm suspecting that even though I have good pressure that I have low volume. Besides a dirty filter what could cause low volume?



And if you don't think that is the issues im more than open for suggestions.



Thanks in advance.






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[NIPs]

Regulator, injectors, cat can cause a lean issue as well as bad O2 sensors

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[Mikel89us]

Everyone also forgets, incomplete burn, aka a missfire whether caused by ignition, fuel, or mechanical problems, will cause a lean burn reading, but in reality be running rich. Smell your exhaust, if it smells like there's a lot of gas in it, you have an incomplete burn in one or more cylinders. If it smells like its really hot ( I don't know a better way to describe it) then you are lean. The first step should be to verify actual lean or rich state. If you know someone with a 5 gas scanner test the exhaust, if its high in hydrocarbons, its rich, high in Nox gasses, it would be lean.

 

[Mikel89us]

The oxygen sensor does not read the fuel, only the amount of oxygen, when the fuel doesn't burn, unburnt oxygen goes past the sensor.

 

[ricardo93]

Try changing the fuel filter just in case, its might help

 

[YungICY]

I changed the fuel filter and it did help a little bit. I also have a pcv on the way just incase I'm sucking extra air through there.



Thanks for the pro tip on the exhaust mikel89. I get a decent wiff of gas every now and then so I could just be dumping fuel and not burning efficiently (getting really bad mileage). And I know the rings on this motor are pretty shot so I guess I could be getting a lot of blow by and therefore a "mechanical misfire" or at least that sounds good in theory haha.



Ill get that pcv in and then take a smell off the exhaust and see where I'm at from there.



Thanks guys.




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[Mark_88]

If you are not sure if you have blow-by, pull the valve cover vent hose off and start the engine. If you see a white wisp of smoke coming out of the valve cover that increases with engine rpm then your rings are probably toast.

Best to do this on a warm day because cooler air can give the wrong impression and turn a small gust of hot air into steam...which is not the same as the smoke you get from blow-by.

 

[YungICY]

Replaced the pcv and, it, combined with the fuel filter seem like they brought her back to normal. Better throttle response, better mileage and a little more power.



Thanks for your help everyone.


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[Mark_88]

Good to hear you cleared it up!

Just a FYI in case you didn't know...the PCV relieves pressure under the pistons and this, in turn, gets you a few more horsepower because there is less resistance on the pistons when they are coming downward...I learned that through researching blow-by...so PCV is very important system to keep your engine healthy...also reduces oil loss through force of air...there can be quite a bit of pressure inside the engine and this forces oil out of every possible exit...like the valve cover especially.