Cylinder 8 misfire under high acceleration

[notamechanicbrad]

Good day mates!

Ive got a misfire on cylinder 8 when I put the truck under a load. The check engine light starts flashing and continues until I let off the throttle partway. Ive changed the plug, coil and fuel injector with no improvement. I am losing some water/coolant somewhere as well. But, there is no water in the oil and no bubbles in the radiator upon startup so I am hoping the head gasket is not the problem. If I leave the truck running just sitting in the driveway I seem to get a hint of gasoline smell. Im guessing that is from an intermittent misfire while at idle. My next step is to replace the electrical plug on the injector as that wiring looks pretty rough (although I see no breaks in it) then to trace that harness back to the PCM to see if one of those wires is the possible problem.

The 3 questions I have been searching for info is ----

1. Could the head gasket be leaking water into the cylinder without water getting into the oil?

2. Is it a common problem for the intake manifold to start leaking in that #8 cylinder? Ive replaced the intake gasket on another Expy but it was leaking at the thermostat.

I try to do as much repair work myself as possible due to the fact I drive this truck from Texas to Florida twice a month pulling a trailer and it usually breaks down on the highway nowhere near a reasonably priced mechanic who is willing to do a repair almost immediately!

I do have the Forscan software as well but am not well educated in how to use it to diagnose this type of problem.

 

[Adieu]

You've almost certainly got a pinhole coolant leak dripping into the well and killing your #8 coil (again) or the wiring there or maybe the injector (I forget if that's also possible).

Coolant doesn't really evaporate and just stays there.

Speaking from experience that this is a thing that happens to these trucks, although mine wasn't on #8 (iirc #4?).

PS or you washed your engine. Don't ever do that.

 

[notamechanicbrad]

Is there any coolant in the intake manifold other than at the very front where the thermostat is located? Where would the coolant be able to get into the cylinders at the back of the motor?

 

[notamechanicbrad]

After some further research I see there are ports at the back of the intake manifold.

Would the next step be doing a compression test? Or should I try and pressurize the radiator and possibly find the leak?

 

[GlennSullivan]

I would do both. Compression and leak down test as well as cooling system pressure test. Compression test first. If you changed the spark plugs yourself, what did they look like and did you notice a difference in the suspect cylinder?

 

[notamechanicbrad]

I worked on the truck again this evening for a couple hours.

I believe I found the coolant leak at the hose clamp where it connects to the thermostat housing. I was able to cut off 1 inch and reattach it.

I also purchased the blue liquid and rented the combustion fume tester. I had already lost some water from repairing the coolant leak so I was able to do the blue liquid test quite easily. Results after 2 tests was no green or yellow...the liquid stayed blue.

And to end the evening I used a noid tester on cylinder 8 fuel injector and got good electrical there so I swapped the coil and spark plug with #2 cylinder.

Unfortunately, when taken for a test drive, I still have the misfire on cylinder 8.

Tomorrow I hope to have time to completely disconnect the wiring on the drivers side and pull that harness out from behind the engine so I can inspect it all the way back to the PCM. I am also considering doing a compression test on #8 cylinder. Im hoping I dont have a stuck valve or other internal engine issue.

 

[notamechanicbrad]

Thanks for your reply Glenn! The plugs were pretty bad. But some had been changed when on the road for work when I had misfire issues. So, some were older than others. I try to keep a couple coils, plugs and injectors in my tools in the truck at all times. But, to answer your question, the #8 plug didnt appear to be rusted or any worse than the others.

I am suspecting the problem is in the wiring.

 

[notamechanicbrad]

Broken valve spring????

The wiring all tests ok. I am definitely getting spark and fuel.

No water in the oil. No oil or bubbles in the water.

Next step...compression test. I rented the tester at OReillys but it didnt come with the adapter for Ford so I ordered 1 this afternoon for tomorrow delivery.

If I dont have good compression but have no oil/water problems...Broken valve spring????

 

[GlennSullivan]

I responded to your other thread with a link. If compression comes up good, it might be one of the 2 intake followers for that cylinder. this issue would not show up in a compression test as the valve with the follower off would remain shut. Problem would not show up under light acceleration as the other intake valve would still be operating. Problem would show up under hard acceleration where the this cylinder is not keeping up with the others because it only has 1 operating intake valve instead of 2.

https://www.youtube.com/watch?v=vE9sCZLaKko&t=37s Start at 3 Minutes.

 

[Calman2k]

I have a 2016 EL and had a similar issue with #3. Turned out the boots on the coils cracked after a plug change. The plugs were shorting against the well and cracking the ceramic. But the crack was so thin you couldn't see it unless you hit it with something dark. It was allowing a compression issue under high load. Took three sets of brand new plugs in only 5000 miles before we finally figured it out. Replaced the coil set and it was all good.
Let us know when you figure it out.

 

[engineer1]

I posted this on another (broken valve spring query) and thought you also might be interested. - Just a thought from a whole different direction. My EB is a gen 2, so may not apply to your situation, but I was having a similar problem and decided to replace the coil packs. When I removed #7 I noticed it was wet on the bottom, but did not have a coolant smell. I came across a thread on this forum about the plastic on the weather seal along the top of the firewall being made in 2 pieces with a joint in the middle that allowed water to drip down onto the engine. I sealed it up with silicone rubber and haven't had a problem since. May be an easy thing for you to just check.

 

[Dustin Gebhardt]

About 4 years ago I had misfire issues that I eventually resolved by replacing all of the connectors for the coils (and eventually all of the injectors, too). Each of those connectors has a rubber ring that's designed to keep the connector clean and dry. Overtime, the rubber fails and, in my case, would cause the plug to make a poor connection. I removed the rubber ring and confirmed that the misfire was resolved. Once that was confirmed, I ordered a set of pigtails and soldered the new one in place of the old ones.

 

[Homer]

Yes double check your spark plug for a very thin grey line. This indicates carbon tracing.(a bad plug). Some thing damaged it if so. Yes a bad boot could do it.

 

[rslynes]

I had the same issue about six months ago while driving through the mountains. Misfire during acceleration going up steeper inclines. Checked about everything others have mentioned here (except compression). Turned out to be an intermittent coil.

 

[notamechanicbrad]

Yeah this repair has been perplexing to say the least. I have another thread titled Broken Valve Spring? and we have been trying to figure it out there. Still misfiring...waiting on an adaptor for my compression tester to fit the skinny ass spark plug holes!

I have swapped coils, plugs and injectors from cylinder to cylinder and still get the misfire in #8.

 

[notamechanicbrad]

Thank you Glenn. I did watch the video. I did remove that valve cover a few days ago and everything looked ok. Timing chain seemed good and tight as well. I went ahead and replaced the VCT solenoid while I had the cover off. 1 thing I am curious about is it possibly a clogged cat. I smell no sulphur smell... But it does have 270k miles and I have no idea how long those cats have been on there. I purchased this truck at around 180k miles or so. I am going to pull the top o2 sensor tomorrow and see if that does anything.

Thank you Calman2k. Yes, I definitely swapped the plug, coil and fuel injector to different cylinders early in this process. i wish that was my issue! But...its not