2003 Taurus 3.0 Stalls while Idling

[RPov]

2003 Taursu w/ 70K miles stalls or runs rough while idling. No fault codes come up when scanned. Fuel pressure ranges from 40 psi when cool to 60 psi when hot. Noticed problem goes away while hood is raised with warmed up engine at normal temperature. When lhood is owered engine roughness comes back. Nothing appers to be touching hood except AC hard line in front RH corner. Also stalls more frequently when running A/C (underhood heat related?). Would like some help to diagnose this problem that appears heat related.

[BroncoJoe19]

Here's a guess.

I'm guessing that most of the sensors that are connected to the engine will be pretty much the same temp hood raised or closed, they'll be whatever the engine temp is. The coil on the other hand is in the engine compartment, and does sometimes fail when it gets heated.

For lack of a better place to start, I would check the coil resistance, and I'd keep in mind that it might check good when cool.

WIndstar coil pack ... how to test
http://www.ford-forums.com/ford-wind...afe-drive.html

[BroncoJoe19]

OTOH... if it is not heat related, a vacuum leak, and or a dirty sticky IAC can cause a rough idle.


What does the IAC do? How does it work?
Ford Fuel Injection » Idle Air Bypass (IAB)
Check and clean your IAC
Ford Explorer IAC Fix .: Articles

Tips for Checking for vacuum leaks.
Some of the sensors and some of the actuators either read the amount of vacuum, or use vacuum to move controls, therefore it is important to the proper functioning of the engine that your vacuum system is fully intact. Otherwise one may get codes falsely indicating that there is a problem with a controller/actuator, or a sensor when in reality it is caused by a lack of vacuum.

Look at your rubber vacuum hoses (they are about 1/4 - 3/8 inches in diameter, if they are dry rotted or cracked, replace them. IF they slip on/off of their connectors too easily, they may have stretched out a little bit, cut the ends off, and put them back on.

You may listen for a leak. Sometimes using a cut off piece of garden hose is a good aid to listen with. Sometimes a cardboard tube (like from gift wrapping paper) is helpful. Just remember that whenever you stick your head inside a running engine compartment, that you are not wearing any loose clothing or jewelry that can get caught.

Another suggestion is to use a spray can of carb cleaner and spray around the bottom of the intake manifold, and the base of the throttle body assembly. IF there is a leak, you should hear a change in your engine.
Keep a fire extinguisher handy, or use water instead of carb cleaner (it works, but not as well.) Be aware that if you use water and the wires get wet and it runs worse... your wires may be bad, and the water is allowing them to arc instead of jump the gap of the spark plug.

Another suggestion is: to take a propane torch, turn it on (but don't light it) and move it over the vacuum hoses and connections. The engine RPM's will increase if there is a leak and the propane gets sucked in.

Courtesy of TheOldWizard ford-forums... Don't forget to remind folks to check the PCV valve, hose and grommet !

Courtesy Ramnasal ford-forums... Clamp off the hose that runs to the vacuum booster (brake booster) or pull it and plug it. It is possible that the diaphram on the inside of the booster may go bad and cause a vacuum leak.

And one more place that is not always obvious is that the vacuum reserve canister in older vehicles sometimes rots out and leaks, but rarely gets checked. In older vehicles it looks like a metal juice can, in newer vehicles it is made of plastic.

Here are some pictures of some vacuum lines in a 1998 3.8L windstar.
Ford Forums - BroncoJoe19's Album: 3.8L vacuum lines