Rough Idle

[GregT]

oh i forgot to mention i don't have any codes to provide i have not put a computer to test it out.. also if i'm on a never ending quest please advice as well hehe.

 

[buildingdoc]

guys how do you know if ur iac valve needs to be replaced?[/QUOTE

I used this and mine tested properly. It does involve tapping the TPS in the later steps and it's simple

Part 1 -TPS Test: Ford 4.6L, 5.4L (P0121, P0122, P0123).

 

[Johnymalangi]

The IAC itself won't create the vehicle run difficult, it will only impact the nonproductive rate. The IAC shouldn't cause a difficult operating situation during generating however. Coils features are the most apparent starting point looking when the vehicle operates difficult all the time.

 

[JEDIDADDYCHRIS]

This is a picture of just the elbow...
And the whole hose is part #F85Z-6C324-AA.

Found one from Ford Parts Depot store on eBay, $44.96 with shipping.

 

[EddieH]

Don't put Bosch Double Platinum Plugs in 4.6 (too hot), stay away from Autolite professional series plug wires-Junk

 

[Pavelow369]

Alright, this is driving me nuts, truck (not mine, family, so I’m committed) 2003 5.4 230,000 hard soccer Mum miles. Cold days would get the P0171and P0174, but I’d clear the code and would be fine. Started running rough a week or two ago with the CEL flashing, code was that multiple cylinder misfire cant remember the code. So I replaced the plugs, which were nasty, corroded, and some of the boots fell apart. I didn’t know you could buy just the boots so I got two new from O’Rilies. Ran worse after and after a while got the P0171 and P0174. Found this forum, which is great by the way, figured I’d try the smoke machine method. Quickly McGyver’d one up using a lit cigar for the smoke source. Nothing…except for the IAC valve….not knowing any better that has an air bleed on it, I replaced it. Ran the same but would stall in drive, most of the time, and still idle rough and around 1500 rpm’s was the sweet spot for absolutely no power at all.. Checked all the vacuum lines, all the PCV lines, changes the PCV valve, even did the propane wand check with no results. Did the smoke check again, thought I saw the EGR valve leaking slightly, so replaced that, and found one of those EGF sensor lines cracked, replaced, cleaned bunch of crud from the TB, seafoam’d the engine…now it runs the same but doesn’t stall any more. Oh every time I work on this I disconnect the Batt the whole time so I assume the comp resets, so I give it some time to warm up and get adjusted.. I’ve disconnected and plugged most of the VAC lines, replacing the ones that looked bad. So the only common thing I haven’t done is actually remove all the PCV lines and that elbow below the IACV, get plenty of suction on the PCV and cant feel anything leaking at the elbow but am going to pull all tonight (found nothing).
I am at a loss…could this be an intake manifold leak from somewhere that wont show up on the smoke test? Should I pull all the plugs again and replace the boots, maybe throw the OEM coils back on with new boots. None of them really felt like they made any sort of positive contact, just sitting on the spring a bit. Fuel filter? Was running ok before…
Posted this on another thread, but havent got any responce.

 

[AnotherEXPYguy]

Solved rough idle

Pulled idle air control valve off cleaned with carb cleaner while I had it off checked the vac line directly under where the IAC sits and there is a 90degree boot that connects a vac line to the back of manifold and the boot was dry rotted and torn so I replaced that put the IAC back on and perfect idle

 

[AnotherEXPYguy]

Try to clean it before replacing pull it off spray it out with carb cleaner let it dry check the rubber 90 degree boot under it while your there it will rott and cause idle problems look on youtube for vids on cleaning the IAC

 

[bedrck46]

The EGR ports in the 4.6 tend to clog more so than on the 5.4 also clean the IAC valve and ports

 

[chuck48]

5.4l '98 EXPY stalls out after start

my '98 stalls after starting when you put it in gear, also when your going down the road and stop it will idles down and stalls out when the breaks are applied. I have removed the IAC and cleaned it and the intake. (no diffrent)