Hey guys.

Been browsing for awhile now. First time posting. I can't seem to get this issue fixed. Little background first:

Bought the truck knowing it needed a little work because it sounded like a diesel when running. So I had the timing chain, tensioners, water pump, etc. replaced and that fixed that problem. Then, a couple days later, a spark plug blew out of the engine. So, I go to do a full tune-up to find out that 3 of the 8 cylinders already had heli-coils in them. I pulled those three and bored out and re-tapped the cylinders using the Cal-Van inserts. This has worked beautifully so far. I also replaced all of the other plugs as well with double platinum plugs. I also replaced all COPs. This got the truck running again and it drives great. No loss of power whatsoever. It just runs like a dog at idle. As soon as I give it throttle it smooths out completely.

It seems like the problem gets worse as the engine starts to get up to normal operating temp. Basically, if I am idling, in gear or in park, the truck shakes pretty bad. It kind of feels like it's starved for fuel or barely missing. I do not have any codes though and if it is a miss, it is completely gone under throttle.

Other things I have replaced within the past couple of weeks:
EGR
EGR vacuum solenoid
DPFE
Both PCV elbows
PCV valve
Air filter
Harmonic balancer

Other things I have done:
Cleaned IAC
Cleaned throttle body butterfly (including EGR ports)
Checked TPS voltage

I'm sure there are other things that I am forgetting.

The idle seems low to me but I'm not sure what is considered standard for the 5.4l. Mine idles around 600 in park once engine is warm and the needle doesn't move despite the roughness felt. Just going by the tach, you would think that the idle was smooth as silk.

I have read a few posts that suggest that it's normal for it to shake at idle because Ford set the A/F ratio low to conserve emissions. Not sure if that's true but it doesn't make much sense because my dad's 2001 Expedition with a 4.6 idles a little higher and is really smooth. Another thing I've read is that there's a PCM refresh that Ford can do to fix this issue. Problem is Ford wants to charge me $85 just to check it out and I don't want to drop anymore money into it unless I'm pretty sure it's gonna fix it.

Any help is greatly appreciated as I believe I have reached the limits of my mechanical knowledge on this.

Truck info:

2000 Ford F-150 XLT
5.4L V8 2V
150k miles

 

seeems like you done a fair amount of work...I kinda agree that the 600 RPM idle (presume that is at operating temp), does seem a touch on the low side. Not super bad either, BUT should be smooth.

in your quest to get this running better...did you ever do a compression test? or vacuum test?
How about changing the fuel filter?? was that done?

 

Thanks for the reply. I replaced the fuel filter today but that made no change. I have done compression tests and everything checks out. Never done a vacuum test but I have checked all of the vac lines and replaced them where they were rotting or loose.

 

what happens if you hold the throttle at 700- 800 rpm ?? Maybe it is just a little slow on idle. If there are no problems above 800 RPM , I would question if you really have anything wrong. .............. maybe you have a very small vacuum leak causing lean mixture at idle ?

 

If idle is all that is the issue, the Intake Air Controller in inoperative and stuck nearly closed. Remove the intake hose from the throttle body and the IAC. Clean the IAC until the fluid comes out clean and test the pintel valve for un restricted movement. Spray clean the throttle body while holding the throttle open until it comes out clean. Here is how idle works; The Crank sensor tells the computer what the RPM is at all times. The computer compares the Idle to a table. If it's to far off, the computer modulates the IAC to correct the idle until it is within 750 +/- 50 rpm. Your idle is to low and is not being controlled. Good luck.

 

I can't hold it at 800. If I slightly press the throttle, it goes to 1200. However, at 1200 it's smooth.

I did clean the IAC already. I did not test the pintle operation. So, I will check that. I did notice when I cleaned it that there is not gasket between it and the throttle body. Is this normal? Also, the way I understand the IAC, if it is not functioning the idle will surge. I do not have this problem at all. Could it still be the IAC?

Also, I cleaned the throttle body pretty well. Next step is to completely remove it and clean it that way I guess. I'm fairly confident the TB is clean though.

One thing I forgot to mention is that I seafoamed the engine utilizing the brake booster hose and I around that time is when all of this started. Of course, I also had the timing chain job done around the same time.

 

There should be a gasket under the IAC.
Surging idle would be if the IAC were functional to vary airflow because that is what it does, change airflow.
The IAC can have another fault you can't see even if clean.
It is a dash pot in actual operation in that there are two springs and a diaphragm.
The solenoid works against the spring tensions and the diaphragm, to have variable setting on a continuous basis.
The diaphragm has a small pin hole to allow pressure equalization for it's movement and movement dampening.
These parts are all located inside the assembly where you can't see them.
If the bleed hole gets plugged, the motor will start then die because the pintel is restricted from full operation. Only fix it to replace in that situation.
The thing your saying about low idle involves airflow.
Normally the throttle stop is set to just allow enough air for the engine to hot idle without the IAC being open at around 550 to 600 rpm.
.
Note the plate is never allowed to fully close because under cool down it will get stuck closed after the throttle body cools and shrinks in diameter same as a carburetor.
.
Then the IAC takes control for about 750 rpm hot idle from the software table so there is some 'range' to adjust air for full idle speed control range.
The total system actually does all the same functions as a carbureted motor except for the automatic control of idle speed and fuel is injected so no choke is needed.
The extra fuel is via richer fuel injection, the extra air is via the IAC larger opening for cold starts, then as the engine heats, these applications are reduced by the computer from feedback off the sensors, mainly the CHT and Ox sensors.
Cold start idle should be high and according to ambient outside temperature. The IAC opens wide for air, fuel is richened and idle speed can go up in the 1200 rpm range, then slowly comes down as the motor heats and the OX sensors take over fuel control.
With this info, you can check for what is not happening.
Good luck.

 

I just changed the IAC with a brand new one and installed a gasket. No change, unfortunately. It is still idling roughly.

Everything works as you described it. Cold start sees the idle around 1200 and then drops as the engine warms up. Once the engine is warm, in park it idles at around 750 and in gear at around 600. It idles rough at 600 and 750. If I open the throttle just a bit, it smooths out. I just have no clue at this point what more to look for.

 

Ok, the next cause of rough idle can be the EGR.
If it is leaking for any reason the idle will get rough independent of the IAC operation.
As soon as the OX sensors detect a lean condition due to exhaust contamination (not an air leak) the ignition timing goes advanced, the fuel injection goes lean.
The result is rough idle.
Remove the hose on the EGR valve.
If the idle smooths out, the EGR is being held off it's seat from a leaking EVR control solenoid.
This solenoid can have a dirty filter under the round cap.
It is a 3 port device such that after it passes vacuum to the EGR, the EVR closes and opens the EGR to air so it will release after having vacuum applied.
Check this operation out.
Good luck.

 

First off, thanks for all the help. I really appreciate it.

I replaced the EGR, EVR, and DPFE already. There was an issue with the EGR system awhile ago as I got a code for "insufficient EGR flow" and it ended up being the DPFE but I replaced all of it.

Another thing I did today was clean the MAF. Didn't help though.

 

Well were running out of common causes and guesses.
Now it's time to put a Scanner on and look at the live data for a clue.
Good luck.

 

Can you give me an idea of what to look for? I'm not really familiar with the more advanced procedures of a scan tool.

Also, I got to thinking about when I changed the plugs and I remember that on a few of the COPs, I was unsure if they were actually seated well. I had no way of verifying that they were actually seated on the plug. Is it best to install the boot and then the COP? If one of the boots worked its way to the side of the plug, it would obviously be misfiring. Is it possible this could not be picked up by them PCM?

Gonna check it out tomorrow but I am interested to know if installing the boot and then the COP is the best way to do it.

 

You should have applied dielectric grease to the boot tips inside and on the end to help the boot find the plug as you set the coil in place plus using your sense of feel to see that the boot sets down on the plug without forcing.
Any misfire due to any cause will be detected by the PCM monitoring of the rotation time as measured by the crank sensor.
Anything that causes lower cylinder pressure over a timed interval will set a code and the CEL plus you will feel it.
Looking at mode 6 test 53 at the misfire monitors may provide some help if misfires are the problem.
At the point your at, your not indicating anything that causes the issue so you need to look more deeply with tools and diagnostics made available for doing so or get a good shop to do the work.
Even with a Scanner you will need to learn how to interpret the data to recognize what is out of spec or even shifted too far.
I can't make it any easier than to explain some things.
The newer vehicles are even more complex.
Good luck.

 

Turns out there was a code for a misfire on #7. Wasn't throwing a light so I assumed there were no codes but when I pulled them on my scanner, voila. I'm thinking it might be due to the COP not being bolted down good enough as it's hard to get to the cop bolt on that one. Gonna go buy a 7mm swivel today, remove it, put some dielectric on it and reinstall. Hoping it's just arcing or something.