1994 Taurus wagon dies

[mschilling]

I have had this problem the last couple of summers. When driving in hot outside temps, using a/c the car dies chugging to a stop. after some time, the car will run and get me home. In cool temps I never have a problem. The engine temperature is always at or below normal. I also have a new problem with the check engine light coming on. The code is; exhaust transducer voltage lower than expected. Any thoughts?

[shorod]

Welcome to the forum!

Thanks for the good details on the issue you're experiencing. You mention you have the stalling when it's hot and the A/C is on. If you turn off the A/C prior to coming to a stop, does the engine still stall? If you are stopped with the engine running and turn on the A/C, does the car stall or does the engine speed drop? If so, it sounds like you have an issue with the Idle Air Control (IAC) servo. This is also referred to as the Idle Speed Control (ISC). The purpose of the IAC is to increase the engine idle speed when the engine is placed under increased load (such as A/C, defrost, or power steering at lock) as well when the engine is cold.

If having the A/C on does not seem to have an effect, then you should consider pulling off the Exhaust Gas Recirculation (EGR) valve and cleaning the valve portion thoroughly with throttle body cleaner. Also inspect the passage from the EGR to the intake. If the EGR valve is not completely closing when then engine comes to an idle, it can cause stalling and would also likely lead to a rough idle.

The code you are experiencing may or may not be related to the stalling you are experiencing. If you know the actual 3-digit code number, that may help in the troubleshooting process. I'm going to guess that they code you describe is related to the Differential Pressure Feedback-EGR (DPFE) sensor which is also a common part to fail on Fords. And as you can probably tell by the name, is related to the EGR system. However, I wouldn't expect this to only cause an issue when the A/C is on, and I would expect it to be less of an issue when the engine is warm than when cold. However, if with the A/C off the idle speed is erratic or rough, then the EGR system is a likely candidate.

-Rod

[mschilling]

Thank you for the reply shorod. The sympton happens when at freeway speeds also. It seems like the wagon is vapor locking. I do shut off the a/c however, it still takes a while before it will run correctly. When I stop after the episode and try to start the car, it fires goes to normal idle and chugges and dies. I ually have to wait about a half hour before it will run again properly, then it runs like there is no problem at all. Thanks for the help.

[shorod]

If you happen to own a fuel pressure guage, it would be very informative to check the fuel rail fuel pressure when the car stalls and won't restart until sitting. Fuel pumps tend to stop working momentarily when warm. Also, if you have crud in the EGR system that momentarily prevents the EGR from closing completely when hot, that could explain your symptoms and code.

You may want to try holding the throttle open slightly when trying to start the car after it stalls hot. Also, for fun, try starting the car with the gear selector in neutral.

-Rod

[tripletdaddy]

If fuel delivery is an issue, and it mostly happens when it's hot, you may be having a fuel pump slowly dying. Others here have explained this phenomenon where the pump works fine when it is cool, but in the summer the temp is higher and the engine recirculating the gas makes it hotter, and eventually the pump can't handle it anymore. Hopefully Rod will straighten me out on this where I've gone astray.

With mechanical fuel pump systems, this phenomenon would occur irregardless of the temp and was caused by a dirty fuel filter that would plug up when under pressure, causing it to stall. Then the debris would drop down while its off, and then open enough to allow the gas through until it plugs up again.

So, it wouldn't hurt to replace your fuel filter if it hasn't been done in a while. It's considered a routine maintenance item, and would need to be done as a matter of good practice if you replaced your fuel pump.