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Lately my '00 f-150 5.4 4x4 has been vibrating at an idle in gear. It's almost like the idle is set just a hair to low. What might cause this? dirty MAFsensor? Cheap gas? Other than that, it's running great, with the exception of a very slight knock under heavy load(cheap gas). I just passed about 134,000 miles too. I am very good about maintenance and use the best parts/fluids available.
Any Idears?
looks to be about 575 RPMs at idle in gear, engine warm. I just cleaned the MAF and intake temp sensors, and added some fuel additive. I'm taking a trip in it tomorrow, so we'll see how it does. I'm not too concearned about it, seeing as how it's not throwing a code and still had plenty of power. Just kind of annoying sitting at a light and it starts vibrating, almost rattling.
I second the vacuum leak. Try reaching behind your intake right near the firewall. There's an elbow/tube/elbow that goes from there to your PCV.The elbow back there is notorious for cracking and splitting. I just replaced mine and was having the exact things going on before I did.
I'll check the elbow, but now I've noticed a slight whine as well... sounds like the IACV... I just replaced that thing a couple years ago. Maybe I can just clean the sucker this time.
Haven't been able to check the elbow yet... been riding my motor cickle for the last week (80 MPG), but I've noticed now that the weather has cooled considerably (30's to50's as oppossed to 70's to 90's) and the IAC valve doesn't seem to be humming, but the idle is still a little low and slight vibration. Still runs great though. I sure enjoy being able to go from 12ft/lbs to 350+...
Id agree that its likely a vacuum leak. My '99 recently develop a signifigant vibration at idle and it had a pinhole in one of the elbows.
I replaced the bad elbow and the vibration went away.
took my wife to the store and after we got back, I took a quick look under the hood. The elbow right off of the PCV valve looks ok. The tube from the elbow is covered with a heat shield/sleeve. The motor was still hot, so I couldn't reach back to the other elbow. I'll check it tomorrow. Does the elbow just pull off likeon the PCV side? Is this a factory/dealership only part? Does the elbow detach from the tube or is it one solid/continuous piece?thanks.
The elbow has a clamp on it, so you will need to remove that with a pair of needlenose pliars.
You can buy the part from any auto parts store. I know that Napa sells them for $3 each.
You will pay $20 at the dealer, but thats because you get the whole hose and the elbow, instead of just the elbow.
On mine, I just took an old piece of hard rubber hose, cut it to length and put it on. It was the same diameter as the original elbow and thus far (knock on wood) its worked fine.
There might not be anything wrong with your truck. I know that my '99 has always had a slight vibration at idle and from what I understand, thats just the nature of the Triton engines.