2011 Ford Fusion 2.5 4 Cylinder Intermittent Misfire
This vehicle has had spark plugs, coil packs and a purge valve thrown at it by the owner but the vehicle still has an intermittent misfire that is slowly getting worse. The owner complained of a flashing check engine light while driving the vehicle over the weekend, and while it's in the shop you can “feel” an intermittent misfire, although it's not a “dead” miss, it comes and goes.
I'm wondering where my diagnostic should go from here and would appreciate some guidance with this vehicle or if there's a common issue that I'm missing. It also has a P1450 unable to bleed up fuel tank vacuum code that the dealership can't seem to fix and I haven't dove into checking out that issue yet, although it could be part of the problem.
Thanks in advance for any help/advice!
Check TSB's P1450 is usually a stuck open purge valve, but it could be the FTP sensor stuck and not reading, or a restricted hose or vent. Any loss of coolant, suspect cyl #1 getting coolant seeping in?
If this vehicle came to me with this story, this would be my first step: Pressurize cooling system over night with spark plugs removed, next day insert endoscopic camera in each cylinder inspect for coolant. Next step: Energize in tank fuel pump, insert 5 gas probe in each plug hole look for h.c. read. Consider these tests as an ohm meter test, if it shows bad you are done, if it passes it…
While I wouldn't completely dismiss coolant in a cylinder, if the misfire is most of the time, coolant usually is not the culprit. On cold start up briefly, yes. But your description points to an issue there cold and hot. What are the fuel trims? Very little to go with here at this point. Have you actually checked which cylinder? Have the correct Ford plugs and coils been installed?
You start where it works for you, I start where it works for me. On this particular type of vehicle with this type of issue I like to base line possible extra underlying issues to negate the possibility of multiple problems. My starting suggestion was based on the limited information given which is the norm, either by omission or incorrect info. Most likely you opine that my thorough approach…
If it works, keep doing it. But yes, I don't like losing that kind of time on a vehicle with a misfire. The vast majority are not coolant related. But I will certainly agree, way too little info for any real direction at this point. You and I have more time in this vehicle.
Compression check easy and quick in cylinder wave form next if compression test inconclusive if all checks good look to fuel injectors
If you can feel it misfiring, I would start with a relative compression check then look at coil current and spark on the scope. Next move on to injector testing with the scope. See how the injector current looks, its easier if you can get more than just the suspect cylinder. So you have a good to compare it to. It makes picking the bad out easier. Considering it comes and goes, I would suspect…
Okay I've gotten the chance to do more testing on this car. I looked into the fuel tank pressure sensor first, and with the hose unhooked from the charcoal canister it still showed vacuum on the live data, so I unplugged the sensor and it immediately went to 4.99 volts and a positive pressure reading on the data, so I have a failed FTPS. Next I did a relative compression test, which showed…
It matters not whether the problem is common not, if you have found the problem, then fix it. My question is, where is the compression escaping, rings, valves, or the cooling system?
I am doing what Rod suggested and leaving the cooling system pressurized overnight to see if I have any coolant in cylinder 1 after sitting overnight.
Albin..i agree.At this point I would do an in cylinder compression check and look at valve issues. Interegate the cylinder.
I would love to do in cylinder scoping, but as of yet I haven’t bought a pressure transducer kit for my Pico.
Most scanners will do a relative compression test per Ford software and give you accurate results from drivers seat. The issue with what your doing via gauge is it's accumulative and not singularly measuring each compression stroke (engine only gets one shot at building compression) . You did possibly find the culprit, but what about mode 6 for confirmation so you don't go down the rabbit hole?…
I had time to investigate further and upon adding oil to cylinder 1 my compression numbers jumped up to over 200 psi after 5 revolutions. I then took my inspection camera and stuck it down the spark plug hole and found small indentations and “pits” for lack of a better word, but no score marks or lines etched into the cylinder walls, only the cross hatching and the ”pits”. Never seen anything…
Low compression and a cylinder that's damaged, means you can stop checking anything further, it needs an engine. I'd never attempt to repair an 11 year old engine.
Yes I agree, but my curiosity has the best of me here and I’d like to at least see what the culprit was. As I said I’m suspecting that the coolant was never changed and has eaten away at the cylinder walls via electrolysis. We’ll see tomorrow when I go into work.
The coolant would be chewing away from the outside of the cylinder. Do a proper leak down. If this is rings you should have crankcase pressure and blow-by gases filling the air cleaner box. Without better information I lean toward verifying if it is possibly a valve problem. We have had more than a few 2.5's in Fusion and Escapes with valve problems.