Hi, I am having issues with my 2000 4.6L Ford Expedition. The check engine light has been on for a while. I am 19 years old and this was my first car. My father at the time said the Check Engine Light was a electronic computer failure and said it was no big deal. The SUV used to shake roughly at 40-50mph and was very rough riding. Later on after the spar plug change, that riding would go away instantly with a few loads of gas

However I always had a feeling that he was wrong. So, I took it to Autozone for a free scan. The p0304 code popped up. So I looked at the possibles causes of this code. They were either spark plug needs to be replaced, coil pack needs to be replaced, exhaust valve issues, or a computer failure. There are 1-2 more issues I forget the name of, but the list is long.

Now, I have replaced the PITA cylinder 4 spark plug, and tested the coil pack. The spark plug was just normally worn. No corrosion or other issues. The coil pack was perfectly with the oHM ranges with a multi meter according to a Expy Manual I have. The other issues are very time consuming, and honestly would take a mechanic to look at.

Now, since those 2 issues I tested and validated the check engine light either would disappear for a week at a time, and then randomly pop back up. The light would pop back up and then start blinking on the highway. This has happened about 2-3 times over the span of a month. The vehicle is smooth riding and doesn't seem to have any issues. I did take the vehicle back to autozone, and the code was still in the Expy.

I am honestly really confused on what could be the issue. I wonder if it's a computer issue since the light disappears and then randomly comes back after a week or so. Any have any idea what the issue could be or what I have to do?

 

A blinking CEL means there is enough raw fuel being dumped into the exhaust to damage the catalytic converters. The P0304 is as you know a misfire which can be caused by several issues. Since you changed the spark plug we can rule that out. The COP although it ohmed out fine can still be a problem. The rubber boot that goes down to the spark plug deteriorates over time and allows spark to jump sideways to ground instead of reaching the spark plug. You can get COPs off eBay for under $10 or you can buy replacement rubber boots for about $3 each. Try swapping the #4 COP with another cylinder to see if the trouble code moves to the new cylinder. If it does the COP is the problem.

 

Sorry for the late reply. I have been busy. So is the blinking CEL and the p0304 code 2 separate issues? I am going to swap the COP to another cyndlider to see if it's the issue.

Does raw fuel being dumped into the exhaust fall under p0304? I believe it actually does, but I could be wrong.

 

No, a blinking CEL means that you have a "class A misfire", which is the most serious type. That's the type that can damage your cats since it's dumping raw fuel into the exhaust. The P0304 tells you there's a misfire on cyl 4.

 

Okay so I'm back. I guess one guy had a similar issue.

However I actually did swap the coil packs with coil packs 1 and 4 being switched. Ironically the code popped back up last night. P0304 was the same code. So, I guess it's not the coil pack at all.

The thing that irks me is that I actually took my vehicle to a stealership and it took them 7 hours to plug my vehicle into a dang computer. They said it was a faulty coil pack. Yea right... 100 dollars down the drain is lovely

P0304 code still popping up after being cleared.

Blinking CEL appears at mid to high rev range and then disappears as usual. This thing is a pita.

 

Since the coil pack and spark plug check out it now looks like you have a bad #4 fuel injector.

 

I did a fuel injector test with a multi meter this morning. I do have a Haynes Manual, but I think this book is half useless considering they didnt give the depth I needed for my exact model and pictures compared to the internet.

However, the reading for a fuel injector functioning properly is 11-18 oHms from what I have read. As a refrence I tested the 1st and 2nd fuel injectors as well for a baseline and refrence.

Fuel Injector 1- 14.5, 15.0 ohms
Fuel Injector 2- 14.6, 14.7 ohms
Fuel Injector 4 ( this is the problem child)- 14.7, 15.0

So, it seems that it is not a fuel injector issue at all now. Im sure I did the test right unless Im doing the wrong test entirely. Here is the webpage I used for my process.

Part 1 -How to Test the Fuel Injectors (Ford 4.6L, 5.4L)

Well atleast that issue is crossed off now! I have no idea what to do next. I really want to fix this vehicle and get another. Im looking for something a bit smaller haha.

 

Well, just because it's electrically sound, doesn't mean it's mechanically sound. Yes, you might have ruled out the little coil inside the injector, but the injector components inside can still be faulty. If you have a Ford VCM scantool, you can run an injector test on it. If not, you can swap the injector from the problematic cylinder to a known good cylinder and see what happens. Doesn't take too much time to swap an injector

 

Think about what the ohms would be if the injector was stuck in the open or closed position...the same, right? So even though the ohms check out, the injector can still be faulty and the source of the misfire.

 

Thanks for the advice.

Now, I recently did the same thinng I did to the coil packs. I swapped the fuel injectors from 1 to 4. I even replaced the orings on all the fuel injectors. I lost a few orings in crevices, and needed them anyways. The fuel rail was a major pain to get on. I secured the fuel injectors on wrong and the seal was not tight. Let's just say the vehicle would not start. If it did, it would shut off. I secured the seals and installed them correctly. The fuel rail screws were the hardest. The rear screw was a PITA to put back on and I had to have my father help me.

The codes came back up last night driving to work. Blinking CEL that disappeared, and p0304 code that I checked last night after I got home. I am at a loss for words honestly. Could I be missing something obvious? I am fairly inexperienced with vheicles at 19. I however try to learn alot as I find it enjoyable.

 

So it looks like you are almost to the end of the list of possible culprits.


To check the valves you could run a compression check. If either valve is not sealing properly that could cause your misfire.


To check out the computer you'll need someone with an oscilloscope to monitor the current wave form on the COP circuit and the injector circuit while under load as the computer drivers turn the current on and off.

 

Okay, well I have ordered a compression guage from Amazon and it should be here by Tuesday at latest. Upon further research of a compression test... Only two outcomes are possible, a lower engine block issue with pistons that would have to be rebuilt, or cylinder head issue. I do not know if a cylinder head issue would require a rebuild or such. If so... This expy is going into the junk yard. Its not worth it financially to have a rebuild cost more than the current deemed value.

The oscilloscope would be hard to find unless I took it to a dealer maybe. I do not know anyone that has such a tool, and the costs for the tool itself seem very high if I bought one for personal use.

My father will be helping me with the test. I will post results. The guide I am using for the test is the link below:

Part 1 -How to Test Engine Compression (Ford 4.6L, 5.4L)

 

Alrighty, I am back once again. Weeks went by before getting around to doing the test. Luckily I have another vehicle so it wasn't a big deal.

Now, I have ran into another issue. I took out 4 spark plugs on the passenger side to be numbers 1-4 on the cylinders. Number 4 is my problem child cylinder as I stated before. I got a compression gauge test kit from Sears. The first two cylinders started fine upon the engine being turned over, by the time I got to the 3rd cylinder the engine would just not turn over at all and there would be a loud clicking noise due to either an alternator or battery issue.

I read that my battery must be on a full charge to be on a compression test. Well, I thought I could get away with a half charge. I guess not. So, I took the battery to Autozone and it turns out the battery is at 11 or so volts, which is low according to them. It charged for an hour and we came back. The results were not so good. Apparently it failed the test and wasn't charged at all. So, even though the vehicle runs, and starts with the battery... I can really do the compression test with a battery that isnt on a good charge.

I am honestly at a loss for words. Should I replace the battery at this point as well? I simply want to figure out the code for once, and I seem to be running into issue after issue.

Am I doing anything wrong? You guys have much more knowledge than I do.

I did have compression reading for cylinders number 1 and 2, but I want to re do them since I feel they were not consistent due to the battery issue and that could have affected the outcome. I dont know if it could though. I did 3 readings on each cylinder

Cylinder 1- 180 psi, 175 psi, 175 psi
Cylinder 2- 144 psi, 135 psi, 140 psi
Cylinder 3- N/A, N/A, N/A
Cylinder 4- N/A, N/A, N/A

 

It's possible the battery is bad, given the fact that it didn't take a charge... But that's not necessarily what caused the battery to drain. Just turning the engine over can do that, depending on how long it's cranking.

As long as the engine was cranking normally, the compression readings would be accurate. Cylinder 2 might be a little low due to slower cranking, I'm not certain.

The loud clicking noise was the starter; since the battery was too far drained, it couldn't turn the engine over any longer. It does NOT indicate a faulty starter.

 

There are a few options if you don't want to install a new battery just yet; local junkyards generally have good working batteries available for about $50. Or if you have a pair of jumper cables, hookup a running car with the Expedition and this will give you a surface charge enough to finish up the compression test.
Lastly, if you really want, you could remove the good battery from your other vehicle and install it in the Expedition just so you could finish the test.

I also think the engine didn't crank long enough to give you an accurate reading due to the low battery. A good rule of thumb is to count to 5 while the engine is turning over, so 5 engine gallops. It's very likely the battery didn't allow you to do that.