2001 Ford Taurus Rough Idle

That sounds like a vacuum leak. Check all of the hoses and the PCV. If all looks good, it could be an EGR concern. For faulty O2 sensors to indicate both banks lean both upstream O2 sensors would have to be bad, not at all likely.

For anyone reading this... we have to repeat "Do NOT rely on parts-store clerk interpreting the codes." IF you are serious about finding problems, get the actual codes and post them here.

On the bright side, at least he didnt try to sell you new O2 sensors.

Just for fun, Tony... when car is up to temp and idling rough... turn it off and disconnect the MAF sensor harness. Then see how it idles, of course that will set the lite.

Dirty MAF manifests in several different symptoms.

Also cleaning the IAC wouldnt hurt

"Tony" wrote in news:1130652422.919790.281500 @z14g2000cwz.googlegroups.com:

My 94 Grand Marq has a real rough idle, and dies sometimes.

After reading your post, I unplugged the maf during ruff idle, and the idle got better.

Does that mean the maf is bad? (I had already cleaned the heck out of the MAF elements a day before, getting rid of my lean codes in the process). 80k miles on the MAF sensor/car.

Also, the iac was cleaned earlier as well.

Maybe it needs to learn new strategy's

I just realized this started happening hours after I got my oil changed. Wonder if they knocked vacuum line loose?

Also what is the IAC?

What best way to clean MAF?

Tom Adkins posted this link for me on another string. Works real well for cleaning the MAF.

IAC = Idle Air Control. Basicly it is a valve that opens when you need to bypass some air past the Throttle body during idle,.....during certain conditions. Mine was full of carbon, but wasn't my problem. I believe something is sending wrong info to my IAC. Reason I think this, is because unplugging my MAF brings the idle up.

However,.... Cleaning my MAF cure ALL of my lean codes and the car runs

I unhooked my battery to reset my computer in my 99 Taurus and it took weeks and over 200 miles to reset everything!!!!!!! BAD MOVE!

Uh... I think it wont help... you have more than one problem, still.

The MAF doesnt control the idle speed in itself. You are referring to engine going to 'high idle' when MAF disconnected, I assume It is also referred to as "limp-in' mode when it does that.

Maybe the Throttle position sensor.. but that doesnt quite fit, either

Rule out vac leak if normal idle is low.

"Puzzled Ed" wrote

Ed, I agree with Backyard. I still think you have a vacuum leak somewhere.

Tom Adkins wrote in news:mJWdnXqnovAH_frenZ2dnUVZ snipped-for-privacy@comcast.com:

.. dont vac leaks result in HIGH idle? always have in my EECIV's

Small leaks yes. Larger leaks cause a rough idle at close to idle speed or lower until it stalls. IIRC Ed still has a rough idle. I can't find the post where he says it though.

Tom is correct,... I still have the ruff idle, with occasional stalls.

But all of my lean codes went away with cleaning the MAF.

Can egr come into play here? It has 80k miles on it, but I am tired of changing parts with no results ($$$).

Ok guys I cleaned MAF Sensor and IAC. It did not help, so I did as you suggested after it got up to temp, I turned it off and disconnected the MAF. It did not surge as before just idled at about 600 RPM for a few seconds then jumped up to about 1000RPMS, would switch back and forth between the too. Should I go ahead and bite the bullett and replace MAF?

Thanks,

Tony

Okay, I feel like an idiot, (but a happy idiot). Mine did indeed turn out to be a vacuum leak,.... the same vacuum leak that everybody and thier brother told me to look for.

I don't know how I missed it, I had looked three times and used mirrors in the process.

But the infamous hose that leads from the Pcv valve, to the manifold, all the way at the manifold,... (I could not believe my eyes) had this big crack right on the elbow, at least two inches long. I am stunned,.... yet without a testdrive, I am convinced that my problems are over.

Thank you so much everybody!

To answer Tony NO! I just wasted another $60 on my MAF replacement (still happy I solved the nagging problem),.... but I advise you to look further for a vacuum leak.

Could you hear the vacuum leak? I have not taken the time to look, but where exactly was your hose that was leaking?

My "where" won't really apply to you, different car. However,.... NO I could not hear it, and three hard searches where I could not see it! Was a fine crack in the hose that came off the pcv valve, but waaaaaay up where that hose hit the manifold. Point being: near the intake manifold like it was, it let way too much "extra" air into the intake manifold, causing all the side effects that I had. (for that matter, I doubt that a leak has to be "near" the manifold to affect you).

I really believe I made the "fine crack" worse (and more visible) when I cleaned out my IAC which required me to fuss-around with the hoses in that area.

But I gotta tell you, my ruff idle is gone, and I can't even hear the motor run at stoplights, it is so very smooth. And that sucker was haunting me for a long time!

Check every single hose that is anywhere near that intake manifold, is what I recommend after my recent debacal.

I want to thank you, I found a used MAF sensor today for $35 before reading your post, car still surged at idle. Was mad at myself. Read your post and went out with more determination to find a vacuum leak. By god I found it. There is an elbow at the top of the PCV that had a huge crack but was barley leaking because of the way it was folding up on itself. I moved it to close leak and volia` no rough idle!!!! Going to see if I can take back MAF sensor tomorrow. Went to autoparts store but they did not have the rubber elbow I need.

Thanks for everyone assistance in this.

Tony

Thanks for lettinig us know of your success.

Happy for ya!