ethanol causing false check engine lights?

[2manyrocks]

2003 Mazda protege (81,000 miles) check engine light is on and the code is reading too lean condition. The shop suggested I might have an air leak at the fuel hose or a vacuum leak. I'm not finding one.

The check engine light on my 2004 Mazda pickup (51,000 miles) came on today showing both the check engine light and a light for an open fuel cap. The fuel cap is tight and I can't find any problems in the hose.

I was told that ethanol fuel has a higher oxygen content. Is it likely that this ethanol gas I'm paying $3.70 a gallon for is causing these check engine lights to go on? It would seem more than coincidence that both vehicles are doing this at the same time.

If I park both fuel injected vehicles and go back to my 1992 Mazda with a carb, what is the ethanol going to do to it?

 

[LD1]

Are you just running the regular 87 gas w/10% ethanol or are you trying to run e-85??

If e-85, that is your problem.

If you are only running the 10% stuff, I doubt that is the issue, but I could be wrong.

Running the 10% stuff shouldnt effect the carb in the older vehichle. It mainly has only been know to cause a few issues with smaller engines. Certain rubbers do not tolerate ethanolvery well. And small engines w/diaphram carbs and rubber fuel hoses can cause issues. Plus ethanol absorbs water. So it has a shorter shelf life. And small engines tend to sit a lot. On a daily driver, this is less of an issue.

 

[MyJoBota]

The protege most likely has a vacuum leak at the intake gasket , common on those.

The B series most likely needs a filter neck. Rusted and creating a evap. leak if you live in the salt belt.

If you cant fix em just blame the fuel:thumbsup:

 

[tcartwri]

Stuck or plugged egr valve will give a lean code. The ethanol is not the answer.

 

[Diamondpilot]

Last car I worked on with a lean code was a Lincoln. Found a leak in the hose for the PCV valve and also a leak in the hose going to the brake booster.

Chris

 

[Car Doc]

Its not the ethanol but I agree with the intake gasket on the Protege being a strong possibillity it should be missing and could be idling real fast also and may have a Po3xx misfire code as well.

Cant say about the truck evap codes can be a nightmare so an easy fix probably isn't in the cards a pro needs to work on that one.

As a rule most all lean codes I see are mass airflow meters either dirty or just bad. my 2c

 

[crazyal]

In the old days they would tell you to just squirt starting fluid all around the intake as the engine was running. Once it found the vac leak the engine would suck in the starting fluid and it would rev up. Nowadays I don't think they want you spraying flammable liquids on a running engine.

 

[Car Doc]

Yup something flammable is the best way still!

I use carb spray or flammable brake clean or a smoke machine thats the preferred way now is use smoke.

I have set engines on fire before using carb spray getting close to a coil or a bad plug wire that is interesting....

 

[PILOON]

In the old days they would tell you to just squirt starting fluid all around the intake as the engine was running. Once it found the vac leak the engine would suck in the starting fluid and it would rev up. Nowadays I don't think they want you spraying flammable liquids on a running engine.

I have seen using a plumbers's propane rig with the nozzel reduced to spew propane around the vacume lines.
When the vacume line sucks in propane the RPM's rise thus locating the leak.

 

[DEWFPO]

I have seen using a plumbers's propane rig with the nozzel reduced to spew propane around the vacume lines.
When the vacume line sucks in propane the RPM's rise thus locating the leak.

I have used this method to detect an intake manifold gasket leak.

DEWFPO