What conditions arise when the engine starts to run lean?

 

Do you mean what conditons cause a lean conditon? Or the result of a lean condition?

It can be caused by low fuel pressure, clogged fuel injectors, dirty air filter, bad o2 sensor readings, vacuum leaks, etc.

The result can be loss of power and lean misfire (which will dump raw fuel down the exhaust and kill the cats) and occasionally it can blow holes in the pistons.

-Jon

 

How does a dirty air filter cause a lean condition? Just out of curiosity.

Signed,
An inquiring mind.

 

Ford4ever,

I meant happens when you have a lean running engine. The reason I'm asking is because my engine is running warmer right now than it usually runs. I just had a cutout installed and this is the first time I have noticed the warmer conditions.

Is a warmer running engine a sign of a lean condition?

It's not hot yet, it's on the R and M, but before it ran on the N and O. It now runs warmer with the cutout closed and opened. Will a bad oxygen sensor make the engine run warmer? Or is the problem all in my cooling system, and the timing is just a coincidence.

 

By the way, where is the temperature read at?

 

...when was the last time you changed the fuel filter??

 

The temperature is read in the lower intake manifold, near the back on the drivers side.

 

Ford4fun,

The last time the fuel filter was changed was probably for it's 30000 mile tune up, which actually occured at around 35000. It now has 47000 miles on it, so I don't think that would be the problem. But if it's easy to replace (don't want to pay the dealer) than I could replace that too.

Would a bad O2 sensor cause the engine to run a little warmer than usual?

 

Whoops, sorry spaceman, a dirty air filter will cause a rich condition.

Yeah running too lean can heat up the engine, and a bad o2 could cause it to run a little lean, is your check engine light on? Theres also a ton of other things that will make it run hot, from a cooling system problem, head gasket, egr valve. I don't think the exhaust cutout would cause it.

How is your coolant level?

-Jon

 

I had my o2 sensor between my cats unplugged for 6 months making it run lean untill eventualy my cats got clogged.

 

Ford4ever,

No my check engine light is not on, that is the first thing I looked for when I first noticed my temperature increase. I have plenty of coolant in my resevoir. I'm planning on doing a complete flush of my cooling system this weekend. The fan seems to be working right too.

Sprocket,

Did you temperatures decrease when you replaced the O2 sensors?

 

A lean condition can cause many symptoms and heat is one of them. I would assume if the condition is bad enough to show a temp swing then you may get some detonation under load while accelerating. There is a fine line, and you may slip through without any detonation.


Having seen you post in the other section, my first question would be the exhaust mods. Was the cutout the only change this time? If so, how close is the cutout to the O2 sensor?

I saw that you are fairly certain you didn't harm the sensor, but I do see a concern if the sensor is too close to the cutout. By design the cutout would likely cause some back pressure when not open, or at a minumum a change in flow. Depending on exactly what it is doing, it may be playing games with the O2.