05 Taurus Idle Problems

So I get this 05 Taurus had it for 1 yr now all the sudden it revs up and down probably a few hundred rpms at times. and some times when you start it it seems to not want to start right up just cranking over till it takes. I take it to the dealer and they replace a IAC valve, seems to take some of it out but only for a week or so. Take it to my local guy he replaces the same thing to no avail. The dealer says it is normal I say he is full of S***. HAHAHAHA What is wrong with this car? No codes no Check Engine light. Just weird idle and hard starts some times. Oh and it did try and lunge a few times. Nothing too bad though. THANKS FOR ANY HELP! This car is under warranty. :)

How many miles on it and which engine does it have? Have you checked the spark plugs or tried a bottle of fuel injector cleaner? Any modifications, such as a K&N air filter?

The IAC would have been my first guess as well. Do you know if either of the shops cleaned the IAC passages, or just replaced the valve? If not, you may want to clean the passages.

How about the EGR valve? Did either shop remove the EGR and verify it is clean and able to close completely?

When was the fuel filter last replaced? That's a routine maintenance item, so it wouldn't hurt to replace that if it hasn't been done.

Also, has anyone inspected for vacuum leaks and made sure that the air intake hoses are tight and that the air filter cover is properly in place?

If you have a K&N or similar air filter, you may have a contaminated MAF sensor. There are rumblings that dealerships may not replace MAF sensors under warranty if the car has an oiled air filter. It would be worth your effort to clean it.

Also, what are the chances this time you could post what you find to fix your issue? It certainly could help fellow members in the future solve their issues.

-Rod

HEY thanks for the reply. It has 47,000 miles with the 3.0 V6, I am offering these suggestions you made to my local mechanic. I will post the findings later.

Okay finally I got my car back. 4 weeks and two dealerships later one guy finds a problem with the altenator outputting funky current causing the rough idle and stuff. I am sure there are more mechanically worded details but I don't thave them available. Hope this helps anyone.:) So they replaced the altenator and all is well.

Interesting. Thank you very much for the update.

I'm suspecting from your description that there was a rectifier diode that went out and was causing a noisy DC output.

-Rod