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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 47620
Experience:  16 years experience
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Ford freestar vacuum issues

Customer Question

Ford freestar vacuum issues
Submitted: 9 months ago.
Category: Ford
Expert:  Chris (aka- Moose) replied 9 months ago.

Welcome, I'm Chris (aka Moose), my normal schedule online is around lunch and after dinner past midnight.

Can you go into more detail?

Customer: replied 9 months ago.
I have a 2004 Ford Freestar with a 3.9L engine. It has developed an issue where it really runs rough on startup and seems to run rough at low RPM's. The check engine light is on...I borrowed a scanner from the auto parts store, and it's throwing a P0171 code (Bank 1 system too lean). I've looked at the typical issues: vacuum hoses, the hose for the PCV valve (cracked rubber elbow) and everything seems to be ok. If I run the throttle from under the hood, I notice what I would call a fairly sound "sucking" sound coming from the back of the engine department, around cylinder 1 (toward the front of the engine). Any ideas on what's back there that could be leaking? What steps should I be taking to troubleshoot this issue?Thanks.
Expert:  Chris (aka- Moose) replied 9 months ago.

The best way to find a vacuum leak is with a can of flammable brake cleaner. Spray shot burst around all seals, hoses, gaskets on , and to and from the intake manifold. If you spray a leak the rpms will change indicating you have sprayed the source of the leak. can you try that.

This is my 1st answer of what can be many. You the website and myself expect you to have a ~~~5 STAR EXCELLENT~~~ experience with my help. At the top of your screen is the rating box that you only get to use once. Please make sure to complete the mandatory rating when ready or reply and say "I am pleased with my answer". Not rating or rating 1-2 stars does not benefit you nor me in any way.

Thanks Moose.

Customer: replied 9 months ago.
I will tear down the cowling tomorrow so I can get at the back...It's hard to access it!
Expert:  Chris (aka- Moose) replied 9 months ago.

Keep in touch as needed

Customer: replied 9 months ago.
I took the cowling off, and listened to the engine...there is a loud sucking noise coming from the backside of the intake manifold. I need to go to the store to buy a can of brake cleaner. I'm not sure if I can get the brake cleaner where it needs to go (tight fit)! I've read that intake manifold gaskets and bolts are a common issue on this motor. How difficult of a job is it as a DIY job?
Customer: replied 9 months ago.
UPDATE: I went and bought a can of flammable brake cleaner. While the engine was idling I sprayed down the back side of the intake area (and all around) and the RPM's didn't change.But, when I hit the throttle from under the hood, there is a definite sucking sound from either under or on the back side of the intake manifold. It sound just like if you put your lips in a "whistle position" and inhale heavily.
Expert:  Chris (aka- Moose) replied 9 months ago.

When you apply the throttle the vacuum goes down. You may have heard the air flow being sucked into the now open throttle body.

I have the steps to remove and install the intake if you want to replace those gaskets and see if that helps. Is that what you want?

Customer: replied 9 months ago.
I guess I'm looking for a recommendation on how to proceed? I'd hate to tear into the intake for nothing. What would be your next step for troubleshooting the engine code I'm getting? Maybe it's not a vacuum issue? Could it be a fuel injector issue?
Expert:  Chris (aka- Moose) replied 9 months ago.

My next step would be a power balance test to see if one cylinder is weaker than the others. Confirming those cylinders are getting good spark, checking those cylinders compression, running a short term fuel trim test to see how lean it is running, checking the fuel pressure.

The MAF sensor tells the engine how much oxygen is coming into the engine. The O2 sensors tell the computer how much oxygen is left over after combustion. Your running lean, that means to much oxygen is detected in the exhaust. Which means oxygen is being sucked into the engine form a source not metered or not enough oxygen is being burnt up inside the cylinder from a partial misfire.

Expert:  Chris (aka- Moose) replied 9 months ago.

Hello again Chris here,

  • I am following up with you to see if you got everything you needed from my answer.
  • I have not heard back from you, so I assume you were not pleased. We're you pleased with my help?
  • If you were not pleased with my help, please let me know by replying so I can help more.
  • This post is coming up on the 7 day mark where it times out. When a post times out, that means it's no longer on my active list (you reply and I may never know it.)

Thanks Chris

Customer: replied 9 months ago.
Chris,Can you send me instructions on replacing the intake manifold gaskets?Thanks,Troy

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