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Discussion Starter · #1 · (Edited)
2000 Taurus SE DOHC (Duratec) Strange noise/vibration in 2nd 1000 - 1750 RPM ~ 40MPH

I have a 2000 Taurus SE DOHC (Duratec)

There is a strange vibration/noise coming from the front under certain conditions. I almost sounds like a rubbing noise.

It usually happens if I am cruising along at about 40mph on a hilly and/or windy road. Once the RPMs fall below 2000 RPM, the noise very faintly begins, is noticeable at 1750 RPM, very noticeable at 1500 RPM, and even more so as it drops closer to 1000 RPM. Once it falls below 1500 RPM, the gas pedal has barely any response and I have to give it a good push to get the RPMs back up. It seems like it should be downshifting, but isn't.

The tranny was flushed a year ago and the tech said it was in good condition.

Any ideas?
 

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Welcome to TCCA.

Did this noise/vibration begin soon after the tranny flush, or after some other event????

Does it do this if you shift out of OD????
 

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Discussion Starter · #4 ·
Welcome to TCCA.

Did this noise/vibration begin soon after the tranny flush, or after some other event????

Does it do this if you shift out of OD????
I'm actually borrowing the car from a family member so I'm not sure when the noise started. They didn't know what I was talking about when I described the issue to them...

If I'm at 40mph 1500 RPM and shift out of OD, it bumps up the RPMs to 2000 so yes the noise stops. However, if I let the speed die down to 25mph (if I recall correctly) @ 1500 RPM the noise is there again.
 

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Discussion Starter · #6 ·
Oooh new info. The check engine light came on and I stopped by Pep Boys to get it scanned. (FYI, Autozone and O'reilly's no longer do free code scans in CA and FL)

Codes P0303, P0171, P0174. Basically, system too lean and misfire on cylinder #3.

I picked up some MAF cleaner and carb/throttle cleaner, so hopefully it's just a dirty MAF and intake. I'm going to do a seafoam treatment afterwards as well. I'll add it to a full tank of gas, run close to empty, then add it to the oil and run 50 miles, then do the smoketacular spray into intake and finish it off with a oil change, oil filter, fuel filter, and new plugs.
 

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Check for vacuum leaks, too, esp. pcv valve and its hose assy., manifold gaskets and #3 cyl. coil (driver firewall).
 

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Discussion Starter · #8 ·
So last night I unclipped the airbox and bent the tube up so I could look inside. I had a clear view of the MAF and the throttle plate. I used some carb/throttle cleaner and carefully positioned the straw so I didn't get any on the MAF. I then took a long heavy duty tent stake to reach down and work the plate open and closed. It worked out well too because the stake was V shaped so I could prop open the throttle plate and put the straw down the V and spray, getting behind the throttle plate and not dripping. Started up the car, revved it a few times. Had my brother come out and rev up to 3k+ RPM a few times while I gave a couple more sprays. Turned it off. Shot the MAF directly a few times with MAF cleaner. Let it sit for a couple hours, clipped it back together. I then recalled a post about resetting the computer, so I disconnected the battery, reconnected, started the car, let it sit in each gear for about 30 seconds ending in park. Turned it off and let it sit overnight.

This morning the check engine light was GONE and stayed off the whole 30 miles / 1 hour commute to work. I only felt a light vibration at one point, but the car seems to be running better. It still idles a little rough first thing in the morning. I think I'm still going to replace the PCV valve and intake gaskets though. I have a hunch something else is wrong. There's a light hissing noise coming from the upper intake manifold that I believe is an abnormal noise.
 

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Seafoam won't help with lean codes, it's probably intake and vac hose leaks as mentioned.
 

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Discussion Starter · #10 ·
Well a about a hundred miles and no codes. The car seems to be running a bit smoother, but the original issue with the vibration is still there. I can also hear a rattling when it happens if I have the window down. I'm hoping thats just a heat shield issue that some others have described. 40mph @ 1500rpm is the magic spot to make it happen.
 

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If the noise goes away at higher rpm, is more prevalent on the passenger side, I like the tranny heat shield as being on your suspect list.
 

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Just fyi I have a rattle noise at those rpms when I use low octane gasoline. Then if I add octane booster it goes away. A good way to tell if that is what is wrong is to go up a steep hill, and see if it gets louder. The plenum could be carboned up too, restricting air flow. I have seen that happen with the DOHC's.
 
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