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OBD code 25 - lean mixture

I am getting OBD I code number 25 on my 92 V6 4x4. I was about to take it in, but got the code to disappear by 1) changing out my dirty air filter; 2) removing and reconnecting the plug wires at both ends; 3) redoing the battery to frame ground ( it was broken); 4) cleaning the battery terminals, and; 5) exercising the air flap in the top of the air filter housing because there was a sucking starving sound in the air hose downstream from the flap. I am not sure which one of these if any of them caused the code to go away. The code stayed off for about

48 hours, but then reappeared.

Also the exhaust seems to pulsing, so it may be a problem that is affecting only some of the cylinders. The idle is irregular, but once warmed up seems to run better.

Any ideas on what thing(s) may be causing this? Could this be a scoil problem? The mixture isn't causing the engoine to knock, but it is close.

P.S. I just put a new O2 sensor in the exhaust pipe (it only has one).

Reply to
crashq
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I forgot to menttion that initially (before I replaced the O2 sensor) I was getting both code 25 (mixture continuously lean) and code 26 (mixture continuously rich) which is why I asked about the coil (or other electronic cause).

Does anyone know what sensor triggers these codes?

Reply to
crashq

We hope you did not touch the tip of the new sensor. The oil from your fingers can damage the sensor.

I have a Ford Bronco that I recently bought, and my O2 sensor throws a code that says it detected a lean condition, then after a few miles the light goes out again. It usually remains out for the rest of the trip, but I see no reason it can not come back on. My guess is the sensor itself is failing and that the lean condition is not correcting itself. I'm thinking that you have touched the sensor's business end, and it is operating poorly. I'd leave it be to see if it burns off ...

Reply to
Jeff Strickland

The O2 Sensor that is located between the exhaust manifold and the CAT is where this is detected. Detecting both lean and rich would prompt me to suspect the sensor. BUT, before I replaced anything, I would reset the codes, then wait for the light to come on again, then compare the new code you retrieve with the previous codes, then set about to fix that particular code that comes from a match.

Reply to
Jeff Strickland

Disconnecting the battery cleared the codes.

How long has it been since the last tune up ? You need to look into why it's not running right as the same problem may be causing the check engine light to come on.

Worn plugs, wires, dist cap, rotor, bad egr, vacuum leak, exhaust leak, low compression, leaking head gasket.........

Could this be a scoil

Not likely.

The mixture isn't causing the engoine to knock, but it is

Why do you think that?

Reply to
Mike

The O2 sensor monitors how much oxygen is in the exhaust to determine whether the engine is running lean or rich. Both codes at the same time would tend to indicate a bad O2 sensor which is slow to respond. A lean code would be set by any condition which would cause an inrease in the amount of oxygen in the exhaust, such as a vacuum leak, misfiring spark plug, exhaust leak upstream from the O2 sensor. A rich code would be caused by excessive fuel in the exhaust such as a leaking fuel injector or tool high a fuel pressure.

Reply to
Mike

It is not possible to touch the actual sensor itself. It is protected by a louvered metal shroud to protect it from contamination.

Reply to
Mike

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