Motorcraft plugs properly gapped and motorcraft wires

 

Update
the rough idle is back.

Its stalled out on me a few times cruising down the highway. I have checked nearly all relays and even pulled my computer to check for corrosion and they were all fine. I have also went through 2 cans of intake cleaner trying to find any type of vacuum leak or intake leak and still nothing.

I did a KOER test and got a code 44 which is thermactor but where to start?

I was thinking about the "Air charge temp sensor" but I cant even find it I recently put a can of BG44k in the tank and the stalling on the highway hasn't happened since.

After sitting over night to drive to work in the morning, starting it first thing it turns over for a while then hesitates, stumbles, shakes then idles fine up to the normal 1600rpm for cold start up and then down to 750-800rpm after a while. But is still rough at hot idle. High RPM's are fine and I can feel nothing remotely close to a miss or stumble.

Any more help would be great fellas. I have the proper motorcraft plugs and wires(routed correctly) and Motorcraft IAC, ignition coil, cap, and rotor.

I have heard mention of an ACT sensor but I can not find it anywhere nor do I get codes for it.

 

well here's another update on this.

Since my last post I havent been able to get the idle smoothed out. So i bought a can of BG44K and two bottles of the Chevron Techron fuel cleaner. I ran about 20 miles worth of fuel when i added that stuff (yes I added both) and it seemed to fix the stumble it had slightly. I parked in my paint shop because I am welding in new fenders and 2 toning it. It sat for about 1 whole week with minor starting and moving to another place in my shop. I noticed upon each start up it smoked a little like it had a build up gas and then was fine. I drove it home 2 days ago to blow anything out that could possibly be in the injection system. Put about 8 miles on it driving it home. By the time I pulled in my driveway, it was idling so SMOOTH that I though the truck stalled and wasn't running. I went out to listen to it and it wasn't missing a beat.

Suffice to say I think it was a dirty injector or many. But I didnt have time to dive into rebuilding the injectors so with $30 in fuel additives I think it fixed my stumble problem and saved me some bend-over work.

 

Excellent news!

Let's hope the "snake oil" cleaner is a permanent fix.

 

Thumper, how's she runnin'? Seems like my "new" 5.8 swap is doing the exact same thing as yours and I've been through all the troubleshooting you have! About to install new f/r fuel pumps as the sender on the front doesn't work and I get the xflow problem when running on the front tank indicating a bad check valve in the rear FDM.

 

Still run great. No stumbling idle but I do believe I have a leaking injector. I'm assuming the fuel cleaner ate a hole through an injector screen

 

Thumper,
I am new to this forum, but have had the same problems with my 1989 F150 5.0 4X4. Checked all possible related sensors & filters, replaced the TB & Air Bypass gaskets, replaced 1 vacuum line and still the same surging, high & kind of rough idle.

I began searching hard for other vacuum leaks in the intake system. I put a rubber hose on my propane tourch head & cracked the valve open. Started the engine and it jumped up to its normal un-Godly high, surging idle. I snaked the hose around where the upper and lower intakes come together and when I got near the rear on the driver's side, the engine spiked up another 400-500 Rpm.

I replaced the upper intake manifold gasket and started her up. Much better, but still around 1200 Rpm and just a little rough, but I could hear a vacuum leak on the driver's side of the engine compartment. Located the leak in the cruise control servo. I plugged the vacuum line to the cruise servo (a larger round chamber located near the firewall on the driver's side). Started the engine and it runs sweet! No rough idle and it is behaving like it should.
Hope this helps. *****Caution when taking the auto trans cable from the throttle linkage! Don't pry it off, just pull the connector forward and it will come off. It stays connected by spring pressure and connects via a "T-Slot" in the little white connector*******

 

I replaced the injectors which were a one hole pintle needle injector with 4 hole injectors and the rough idle went away. Idles really nice and smooth I believe I now have an ignition problem. From sitting for a couple of days because I don't drive it all the time, when I go to start it it will crank a while before starting up. I'm thinking my act sensor is out of range because when its hot it takes 2 tries to start. But when cold it fires right up.

 

Thumper,

I do know from experience that a bad map sensor does cause the same problem. I had that problem, tested the MAP sensor and it started & ran fine. Just something to ponder........A mechanic buddy of mine said the reason it starts hard when it's warm is because heat in the engine compartment causes circuit boards to expand.

 

What was the injector part number by chance?