2000 f150 5.4l.. truck idles rougher than dog ****. 1500 rpms and higher runs fine. I've gotten 7 codes so far..p0136 p0300 p0174 p0171 p1151 p1131 p0156. I've cleaned the maf and tb. Replaced iac and pcv valve. And somewhat cleaned the pcv hose. The elbow is fine from what I can tell. I replaced the intake manifold about a month ago and came with different setup for pcv valve in the rear so everything there is good. Thinking about replacing the pcv hose itself but having to order it. I'm all out of ideas of what to do next other than to take it to the local mechanic..

 

I think you're on the right track with a vacuum leak. That or the egr system is faulty somehow. There is the slim possibility that the O2's are bad.

 

Replace all the ignition coils. Granted that will help it 1000%

 

I replaced the coils when I replaced the intake manifold..

 

I'm thinking EGR as well. My '94 T'bird was frustrating me for the longest time. It sits most of the time now since I've gotten the truck. But before that I had a '91 Tracer LTS 5-speed that was my DD and winter driver. One spring when I woke up the T'bird, it had a miss while idling that I had a hard time finding, and power was off too. I put Lucas injector cleaner in it thinking maybe an injector was dirty. I use it from time to time. It had seemed to smooth out a slightly rough idle before. At the same time I "again" was spraying some GumOut Throttle body cleaner into the TB. On this one occasion I removed the EGR tube from the intake and sprayed some down to the EGR and the engine stalled. Hum? So I went ahead and really dossed it up and let it sit for a few minutes. Had a hard time starting it but once it did, and I revved here up a bit the idle missing was nearly gone. Not saying that's the case with your 5.4, but it's another place to look. Good Luck....

 

So did some tinkering and found that the pcv elbows are pretty deteriorated on the inside but no holes. The elbow coming from the pcv valve itself has collapsed and is being sucked closed. But when I pull the pcv valve/elbow out it sucks just fine? Could there be an issue with the pcv system? while idling I checked the other end of the pcv system, the hole on the driver side valve cover and there seems to be no suction coming from it? Should there be?

 

Check your O2's and cats.

 

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