2002 Mercury Mountaineer Rough Start

[meyersm15]

Hi guys. I have been searching this site as well as everything else I can find and cannot find an answer to what is going on. Hopefully someone can help.

I have a 2002 Mercury Mountaineer with the 4.6L V8. I am in the process of selling it because I bought a 2005 with lower miles, but I need to fix my problem because most people aren't interested.

If the vehicle has been sitting a while and the engine is cool, it starts perfectly. When I go for a drive for a while and bring up the engine temp is when I have issues. With a warm engine, the car turns over just fine, but then the RPM's drop very low with the engine almost sputtering. They bounce up an down a bit until it idles normally. If I step on the gas and bring the RPM's up, the problem goes away immediately. Also, if I step on the gas revving up to about 3,000 or 4,000 RPM's immediately upon starting, the RPM's don't dip down. The engine has died a few times when the RPM's drop super low. I'm just not having any luck figuring out what's going on and would appreciate any feedback anyone has had.

Thanks so much for you help!

 

[lincolnshibuya]

start cleaning up the throttle body, iac and maf sensor, see if that makes a difference.

 

[swshawaii]

http://www.explorerforum.com/forums/showthread.php?t=339793&highlight=iac

http://www.explorerforum.com/forums/showthread.php?t=217062&highlight=throttle+body+cleaning

 

[meyersm15]

Hi guys. Thanks for the feedback. I took the idle air valve off and it was pretty black. I spent quite a bit of time cleaning it and it didn't change anything. I even bought a new one just to make sure that it wasn't so gunked up that I couldn't get it clean. Still no change. I looked at the MAF sensor, but it looked perfectly clean and shiny, so I didn't clean it because I didn't have the proper cleaner. Any other ideas what could be going on?

One other thing I noted while testing a few theories is that I will not have the issue when the engine is warm if I restart the vehicle right away. If I wait about 2 minutes, then start it, the rpm's jump all over nearly killing the motor.