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Rmldaytona
Rmldaytona, Certified Technician
Category: Ford
Satisfied Customers: 1887
Experience:  ASE Certified. 13 years Automotive Experience.
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Ford Freestar Limited 2004 Ford Freestar van idles rough like

Resolved Question:

2004 Ford Freestar van idles rough like it was running out of gas. Has new plugs/wires. As the accelerator is depressed- engines runs very smooth
at higher rpm than idle. If the accelerator is held firm at say 2200, or even 3000 RPM after a few seconds the engine will rev- up on its own - maybe 200-300 RPM , and then gradually back down. I'm thinking oxygen concentrator since I had this same symptom in a 1994 Chevy pickup and replacing the O2 sensore remedied the problem. Sources on the web say it could be that, or a cam-shaft sensor, or a catalyst sensor. Any suggestions pointing in the correct direction ? Thank you ahead of time.
Submitted: 6 years ago.
Category: Ford
Expert:  Rmldaytona replied 6 years ago.

rmldaytona :

Hello. I would be glad to assist you. Which engine is in your vehicle? 3.9L or a 4.2L? If you don't know, what is the 8th digit of the VIN number. The VIN number can be located on the driver's door/jam and the dash by the bottom corner of the driver's side windshield.

Customer:

I am going to have to call my Step-daughter and ask her the engine size. Please hold for a couple of minutes.

rmldaytona :

Take your time

Customer:

It is a 3.9 L engine.

Customer:

I apologize . I said that I suspected the O2 "concentrator" - I meant O2 SENSOR!

Customer:

I wouldn't think that the engine would idle-up so smoothly if a "coil", or ignition module" device was at fault.

rmldaytona :

Thank you. The problem here is most likely a large vacuum leak causing a lean air mixture. Most common (very common) are the crankcase ventilation hoses to crack or collapse causing a vacuum leak. Also, the air intake tubes crack and cause this problem. The clamps on the air intake tubes must be tight and secured properly to seal correctly. There are 2 of the crankcase ventilation tubes one to each valve cover. Inspect them closely looking for any cracks or holes. Make sure they are on as well. There are also a number of other vacuum hoses that can rip/tear causing vacuum leaks. All vacuum hoses are of little expense to repair. Other possibilities are a leaking intake gasket. These are common to fail as well. Intake gaskets can be a significant expense $300 to $400 depending on shop rates. It is unlikely that the oxygen (O2) sensors are causing this problem. The best way to diagnose this problem is using a smoke machine. This is a machine that releases smoke. By hooking up a smoke machine to the air intake, you can easily pinpoint any vacuum leaks.

Customer:

OK - then, that's interesting - not what I suspected, but it makes sense. Your efforts are appreciated. /thank you so much, and I do "accept" your opinion.

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