'98 Expedition 4.6 Random Misfire

[ctown2]

I have a '98 expedition with 144K miles. I need some help troubling shooting a random misfire in the #8
cylinder(s). About a month ago, I had the following CEL codes; #8 misfire, system to lean (bank 1&2). I changed out the plugs, wires, and coil packs, and reset the CEL. I never got any codes tell about a week ago. This time it was simply a #8 misfire. Changed the plugs and wires again, and tested the coils with my multimeter (showed the right resistance on both primary and secondary).

Now after reseting the CEL light again, my wife drove less than 50 miles and it came back on with the following. #8 & #1 Misfire, system to lean (bank 1 & 2), and EGR valve. I have not had the chance to pressure test the cylinders to isolate the problem, but that is next on my list of things to do.

Here's my question, are the misfires happening as a result of EGR? I noticed that it idles rough under 1000 rpms, but over 2000 rpms it seems to smooth out.

Here's the actual code numbers that keep popping up;
308 (Misfire on #8)
401 (Exhaust Gas)
301 (Misfire on #1)
171 (System to Lean Bank 1)
174 (System to Lean Bank 2)

I've replaced the following; plugs, wires, coils (under 1000 miles on the coil packs), EGR valve pressure sensor, EGR control solenoid. I bench tested the EGR and it holds a vacuum with compressed air ran through it.

Any idea what I'm missing? Or next steps to take?
Craig

 

[Bedrck47]

Have you pulled the throttle body and cleaned out the exhaust port in the throttle body.
There is a good video on youtube about this.

Check the hoses that go to the DPFE sensor

 

[Bedrck47]

http://www.expeditionforum.com/f42/about-egr-pcv-dpff-evap-iat-tps-maf-23583/#post191356

http://troubleshootmyvehicle.com/ford/4.6L-5.4L/troubleshooting-p0171-and-p0174-page-1

 

[Bedrck47]

I would first pull the throttle body and clean the exhaust ports They are well noted for clogging up with carbon That should take care of the P0401 code and also may cure the other codes. After cleaning the TB clear your codes and drive the expy to see if any codes reappear.

 

[ctown2]

Have you pulled the throttle body and cleaned out the exhaust port in the throttle body.
There is a good video on youtube about this.

Check the hoses that go to the DPFE sensor

I have not cleaned out the throttle body, but I did notice when I pulled the EGR off there was some carbon build upon the EGR and the throttle body.

Could this be causing the misfires?

 

[Bedrck47]

Possible The TB on the 4.6 engine has two small ports thru it. They clog faster than the 5.4 which has one larger port. As I said earlier That would be the first thing I would do. Only needs two gaskets and throttle body cleaner. Not an expensive repair Just time consuming. Also while you have it off check the hose that connects to the rear of the TB. P0401 is low egr flow and if those ports are clogged that will cause low flow.

Keep the forum posted as to the results

 

[Bedrck47]

Read the information in the links I posted earlier. Some good information in them

 

[ctown2]

Thanks for the tips. I will pull apart the throttle body & EGR and clean them both. Should I use any special 'throttle body' cleaner, or would a general purpose cleaner like MEK work?

That link will point me in the right direction. I used that site earlier to try and trouble shoot the EGR code, and that is what lead me to bench testing the EGR. When I took off the EGR it has some carbon build up, but I wasn't sure if it needed to be completely clean so I cleaned it a bit. Sounds like I should have cleaned it a bit more and the throttle body at the same time.

Should I take the throttle body off to clean it, or just keep it on and clean the air intake side and EGR side?

 

[Bedrck47]

Use Throttle Body Cleaner in a Spray can. You can get it at any auto parts store. You most likely will need two cans if they are badly clogged. Wear gloves.

Watch the following video

https://www.youtube.com/watch?v=XvMyPL5d7kg

 

[ctown2]

I cleaned out the throttle body after taking it all off. Both of the air intakes from the EGR were badly clogged, one was so bad that not even compressed air would blow through. I couldn't believe how clogged up both of them were!

So I cleaned everything really well and reinstalled. Truck ran a lot better, the rough idle is gone, and it a lot more power. However, after driving around the block and reving the engine a couple of times the CEL came on again, giving me the cylinder 8 misfire. I came home, popped the hood and pulled out my multimeter. Out of curiosity, I unplugged the #1 cylinder fuel injector sensor, and checked the voltage coming out. I haven't looked up the specs yet, but from the voltage readings it seems to be getting a signal (goes from 13-14v to 8v, to 10v).

I did get the freeze frame data from the cylinder 8 misfire.
Fuel System 1 CL
Fuel System 2 NA
Cacl Load % 56.47
ECT 71 degrees
STFT B1 7.81
LTFT B1 25.00
STFT B2 3.13
LTFT B2 25.00
RPM 1647
Speed Kmh 28

I haven't looked into what the data means yet, but I think I have cleared the EGR & lean code finally!

 

[ctown2]

So I'm not sure if it's good news or bad news....
I check the fuel injectors and they are all good. I even pulled the #8 off and double checked that it was getting the right resistance readings.
While I was pulling the fuel rail off, I pulled the #8 plug. The #8 plug was black, and had a layer of oil that wasn't on the other plugs. After taking all the plugs off, I did a dry compression test. I did this with the engine cold.
Cylinders 1-7 were 125, Cylinder 8 was 0.
I then did a wet test with a small syringe of oil in the spark plug hole. Cylinder 8 still had 0 compression.

So, I'm guessing the cylinder head is shot?
This kind of sucks as we just bought this thing about 3 months ago and it 'was' running good until recently.

 

[stamp11127]

You could use an air hold tool to apply compressed air to the cylinder. If the air comes out of the intake or exhaust the head needs work. If it comes out of the crankcase then the rings are toast.

 

[ctown2]

I was looking up leakage tests as well, but I wasn't sure if it was worth measuring the specific amount of leakage, or to simpler understand if it's the head or crankcase. I'll fire up my compressor in the morning and see what I can come up with.

 

[ctown2]

So I tested #8 this morning, and I got air coming out of the #7 cylinder. I also had a little bit of air coming out of the intake, but it wasn't nearly as much volume as the #7 cylinder. I reversed the test by putting air into the #7 and got some air coming out of the #8. Not as much as from 8 to 7, but still enough that I could feel it on my finger. The next thing I did was to plug to go back to the #8 cylinder and plug the #7 with the spark plug boot. When I did that, I got a lot more air coming out the intake (pulled off one vacuum line).


Sounds like a head gasket replacement is in order? Or am I looking at two separate issues; head gasket and intake valve?

 

[ctown2]

To follow up from earlier today. My father in law came over, and we reran the leakage test. Neither one of us heard anything escaping from the #7 cylinder head, but we both heard and felt air leaking from the intake side. So, we started pulling off pieces to get the valve cover off to see if we could see anything wrong with #8. Ran into trouble with getting the EGR exhaust pipe off the exhaust manifold. Soaking the piece overnight to see if it will break loose. Is the EGR exhaust pipe a 26mm or 28mm head, as we were using an adjustable wrench and it kept slipping.

 

[ctown2]

Update on trying to find the problem. Pulled the EGR hose valve off after soaking overnight. Ended up buying a 27mm wrench to use, as the adjustable wrench just wouldn't get tight enough. Broke free after a couple of hard pulls. My FIL and I then tried to find TDC on #8 by hand spinning the crankshaft, and watching the camshaft (had pulled the valve cover off). When we thought we were getting close, we hooked up the compressor and blew air through the #8. We then spun the crankshaft, opening and closing both the intake and exhaust. As one of us spun the crankshaft the other guy listened for air leakage from both exhaust and intake sides. Through this process, we found that the intake side was leaking a lot of air. Although we never could pin point TDC, but we never once stopped hearing air leaking out of the intake. As we cranked through, we could feel the pressure difference from when the intake was open, and when it was closed. So, we are pretty confident that it's the intake valve on the #8 that is causing the loss of compression.

Anything else that I should double check before I start the process of pulling the whole head off? From what I've read online, it seems to be 'doable' to the average mechanic (myself), but just takes a lot of time to remove the whole front end.

 

[ctown2]

Pulled the head off after a couple of partial days of tear down. Found out today that the culprit is/was a bent #8 intake valve. In the process of cleaning the head to see if any visible cracks are present, but I may end up just getting rebuilt heads.

 

[Widdershins]

May I ask why you checked #1 when your CEL was reading #8 ?
and may I ask when allof this was starting were you having drivability issues prior to getting a CEL ?

 

[Widdershins]

Does ANYONE know of / or found a code reader that has Ford Specific codes?
We are a Ford Family and as hubby is old school, these new fangled machines are driving him nuts !
Thanks for your help

 

[ctown2]

May I ask why you checked #1 when your CEL was reading #8 ?
and may I ask when allof this was starting were you having drivability issues prior to getting a CEL ?

To answer your questions. I don't drive the truck on a regular basis, so I wasn't the one that would have noticed anything regarding driveability. The few times that I drove it before I pulled the code, I noticed a little loss of power at certain RPMs, but nothing I could pinpoint. If you read the whole thread from the beginning, you will noticed that I was having both a misfire code and a EGR code. I thought initially that the two were related.
The first thing I did was change plugs, wires and coils.
The second thing was to figure out why I got the EGR code. Found out that intake ports were clogged up, and the truck wasn't getting very much air. Cleaned that out, and the truck ran fine for a short while, before I got the misfire code again.
The third thing I did was to pull the plugs, double checked coils, and wires. Double checked to make sure that it wasn't an ignition problem. Solved the ignition step.
Then the fourth step was to figure out if it was a fuel problem. Checked all the fuel injectors and found it was fine.
Finally, I did a compression test on ALL cylinders, and discovered that #8 had no compression. Then, I did a wet compression on #8 to see if it was rings or valves. It came back to valves.
So than I ran a leakage test on #8, learning in the process how to find TDC for #8. Ran leakage test and discovered that it was leaking out the intake. So no compression = bad intake valve.

In order to pull the heads completely off, I had to get the timing right so that when I went to reassemble the valves wouldn't be hitting the cylinders. So that required finding TDC on #1.

I currently have both the right and left heads at the local machine shop were they are going to do a pressure and vacuum test. If they are good, I'm having them rebuild them.

Does this answer your question?