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Bad misfire on cylinder

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Old 11-10-2013, 07:32 PM
Andrew7dg Andrew7dg is offline
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Bad misfire on cylinder

1998 Ford F150
5.4L Triton
225,000 mi

I was driving it the other day and it started hesitation on me like a misfire. The check engine light was flashing on me. I went and pulled a code and all the code was for an evaporation problem. Didn't find a check engine light for a misfire.

Thinking it was the plugs, I FINALLY got the courage to swap the plugs myself. I did it! I am proud of myself because I was dreading it but it really wasn't that hard. HOWEVER the problem is still there!

Pulled wires and narrowed it down to cylinder number 4 (closest to passenger)
I replaced it with a good coil, problem still is there.
Replaced Fuel injector. Problem is still there.
Checked electrical connections to coil and injector and all is good.

I think it is mechanical. I am GUESSING that if I put a compression tester on it, it will show that it has low compression but that is just a guess. There is a tick but I think that is more of an exhaust leak then anything else.

What goes wrong with these motors? I haven't found too many engine like this go bad from a valve. Doesn't mean that it doesn't happen but I am a little depressed that after I got the plugs replaced that the truck now is junk.
Anyone with ideas? I don't want to junk the truck so soon yet

Thank you for your time!
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Old 11-10-2013, 07:59 PM
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Cubawashere Cubawashere is offline
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you are jumping all over the place to conclusions that are unsubstantiated. First of all you need to let us know what the code was to do the proper procedure associated. Always start basic, and jumping to change plugs because it "felt" like a misfire was jumping the gun.

Because you sneeze or have a runny nose doesn't necessarily mean you have the flu... need to do all the checks to find out it's not a cold or allergies etc
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Old 11-10-2013, 08:14 PM
Bluegrass 7 Bluegrass 7 is offline
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You made two mistakes.
First what was the code and is it still in? It needs to be taken care of as the possible cause of your issue.
Second, likely there is no cylinder misfire at the moment because the PCM would have detected it.
Why; the PCM measures crank rotation time on every cylinder during their ignition/ firing stroke. The crank sensor does the time measurement for every cylinder.
Any cylinder that takes longer that the average for all the cylinders in the history tables is a 'logical' misfire for whatever reason even for low compression cause.
The PCM never misses monitoring this action.
You chased an issue in what you did and not found one because it's not there.
The code would have been one between 301 to 308 or 351 to 358.
As last resort a Scanner capable of looking at mode 6, test 53 at all cylinders misfire records would verify any cylinder with a high misfire count.
What say you?
Good luck.
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Old 11-10-2013, 10:09 PM
Andrew7dg Andrew7dg is offline
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The light flashed while I was driving it (while it was hesitating) It stops when I pulled into the parking lot.

I apoligies a head of time because I don't have the Code number.
I know it is the evaporative system error. That code has been in there for a couple of days before all of this happened. There was no other codes stored. I thought it was a loose gas cap. After I scanned it I erased the code. Code hasn't come up yet.

I didn't get any other code from the computer which is the fustrating thing. I would have thought that something would have been stored. Thats why I went to the pulling of the connectors seeing which cylinder made the engine run rougher and which ones didn't. The one that didn't is that cylinder.


I replaced the spark plugs because they were long overdue (they looked pretty bad and the gap was wide). I thought misfiring was a symptom of bad spark.

What you two are telling me gives me hope that it possibly might not be a bad cylinder. That something else might be the culprit?

What steps should I take now?

Is it possible that it could still have a low compression cylinder firing at the correct moment but yet working enough where as not to throw a code?
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Old 11-10-2013, 11:06 PM
Bluegrass 7 Bluegrass 7 is offline
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Clearing the code causes the computer to do full diagnostics of all systems.
The fuel tank diagnostics is very complex and takes a long time to meet all testing conditions so the fault may return in time if there is one..
A misfire you feel as a drivability issue, is a total lack of cylinder fire not slightly low compression you likely would not feel as anything but the motor down on power if your good at long term comparison..
A CEL flash due to a missing cylinder is telling that raw fuel could burn in the cats and melt them if it goes on to long.
Get a handle on the cause before changing any more parts.
Good luck.
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Old 11-11-2013, 01:34 AM
deputydog03 deputydog03 is offline
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My suggestion, for what it is worth, go ahead and do a compression check. I have worked on 2 of these in the past year, both had broken valve springs.
The first started missing. The check engine light came on and went off, and came on, then flashed. It was showing different codes every time we checked it. I figured out it was a misfire on one of the cylinders. Coil, boot, plug didn't fix the problem. As I was 200 miles from home I did find a spark plug to put change to, but ended up moving coils from a good firing cylinder to the bads cylinder, with no change. I swapped injectors from a good cylinder to the bad one, no change. So I limped it home. As long as I held the RPM's high it smoothed out. Compression check showed less than 35 pounds on that cylinder. It had a bad valve spring. I elected to swap engines.
The next one I didn't check any of the codes, the owner had already had it checked and her mechanic said it had low compression on a cylinder. I think it was the third one back on the left bank on both engines. I did a compression check to verify and found low compression. Pulled the valve cover and found a broken valve spring. With the special tools it was a breeze to fix. Fill the cylinder with compressed air, nylon clothesline rope will work too. Then use the special spring compressor and change the spring.
It sounds like you already unplugged the cylinder and verified a miss on that cylinder. Is there really any need to keep checking codes? Go ahead and run a compression check if you have a guage and see what you have.
The last broken spring we fixed we had a mechanic bring a bore scope out and look at the cylinder. That might be an option if you know someone that might have a scope.
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Old 12-04-2013, 09:30 AM
Andrew7dg Andrew7dg is offline
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Truck is fixed

After I replaced the spark plugs it was still misfiring. Looking at the top of the COP and showing that they were the factory COP I took a chance and decided to replace them all.

The truck runs really good now! Possibly better then it did before all of this happened.

For a note, truck misfired but never threw a check engine light which is kind of odd to me considering it was running really rough.

Just wanted to show the solution to this problem
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