I have a 2007 4.6, when I first got the truck it had a hesitation/rough idle. Its not throwing any codes at all and I thought it might have been related to the timing components. I replaced all the guides, tensioners and chains, as well as plugs and made sure all of the COPs are functioning properly. The problem persists, and for the life of me I cant figure it out. I have also cleaned the maf as well as ran seafoam through the brake booster. I have a pretty expensive scan tool that will give me live values of pretty much anything engine related. This is only a problem at idle, there is no problem driving the truck and no misfire under any type of load. Any suggestions as to what I should look for next?

 

I'd be looking for a vacuum leak. Fits your symptoms.

 

that will usually have a code though. either p0171, p0174 for both

 

Exactly, I have looked for vacuum leaks already and never found one. All of my coils are functioning properly and my injectors are functioning within normal limits according to my scanner. I’m really at wits end here as I have no codes, but this hesitation/rough idle is killing my OCD lol

 

Well there's been plenty of guys that also never had the lean codes but found a vacuum leak behind the manifold or at the air filter tray and it resolved their issue so it's worth a look if you're out of other ideas.

 

good point

 

do you have any kind of scanner that you can check fuel trims with? Most basic code readers can do it if they have a data stream function. That would tell you if you are running lean maybe just not past the threshold to set a code.

 

if I remember correctly my fuel trims were within spec, but I will check again I have a pretty involved scan tool which lets me do just about anything including bleed abs and a bunch of other stuff.

 

So I hooked up my scan tool and went for drive to check the fuel trims, short term bank 1 and 2 hovered close to zero around 1-3% for the entire drive, long term bank 1 and 2 was below 1% for the entire trip as well.
There were occasional spikes in the short term banks to about 7% but it immediately came back down to the average numbers.
I had 0 fault codes however I did have a detected misfire but I believe it was upon startup as it detects the misfire based on RPM. There were no fault codes on the injectors and the spark duration of all the plugs were about the same although it varies slightly but nothing abnormal.

What else should I look for using the scan tool?

I bought a can of starting fluid and will spray around looking for vacuum leaks tomorrow.

 

how many miles?

have you removed and cleared the TB?