Misfire need help !

[krzstruyk]

Hi everyone did a tune up plugs and coil boots, after this I starting having issues (nonissues before other then some surging under a lot of throttle but no code previously) then I had a code for misfire on Cylinder 5 , replaced the coil and seemed ok until I hit 45-60, ordered all new coils installed them and the issue still persists I moved coils and plugs but it’s now consistently showing on cylinder 6. I’m puzzled as I had no issues before and did a tune up and now have issues. My only thoughts now is bad or dirty injectors ? Could this be the issue ? Any thoughts ?

 

[JasonH]

Check the plug gaps. They should be below .032.

 

[krzstruyk]

I will check that tomorrow that was the next thing I was reading about

 

[krzstruyk]

Re gapped all the plugs they were way out of spec but issue is still persistent swapped plugs around but seems to be moving with the coils, I bought new aftermarket coils from rockauto, I then put the one back in (checked resistance and the original coils matched the resistance as a new oem that I had) any tips on what to check next

Is it possible it is a injector fuel issues , happens between 45-60 mph when it’s under a good amount of acceleration as if it’s starving of fuel maybe or not getting the correct spark

 

[99WhiteC5Coupe]

Hi everyone did a tune hit plugs and coil boots, after this I starting having issues (nonissues before other then some surging under a lot of throttle but no code previously) then I had a code for misfire on Cylinder 5 , replaced the coil and seemed ok until I hit 45-60, ordered all new coils installed them and the issue still persists I moved coils and plugs but it’s now consistently showing on cylinder 6. I’m puzzled as I had no issues before and did a tune up and now have issues. My only thoughts now is bad or dirty injectors ? Could this be the issue ? Any thoughts ?

Did you use OEM Motorcraft spark plugs, coil boots and coils?

You said you “did a tune”. Did you modify the existing vehicle computer?

 

[LokiWolf]

We need to know year, as that would tell us motor, since the assumption so far appears to be it is a 15-17.

Yes, if you are tuned, by who is important. If the issue started after the tune, and the plugs are now gapped properly, then I would do some logging and send it to your tuner.

If you are tuned, you should be more like 0.028 for your gap. Especially if it is a Sport/Performance tune, and you are running 93.

That is also a factor. If this is indeed a 15-17, and you are tuned, most likely the tune is written for 91+. If you are running 87, that could be an issue.

PS - There are many plugs out there that are equal to or in MANY ways superior to OEM Motorcraft plugs, so knowing that part number and brand would be helpful in diagnosis.

 

[krzstruyk]

Sorry not sure where I had the typo but NO tune it is stock 2017 3.5l I did oem plugs boots and then when I had the issue I ordered standard motor coils from rock auto , but I checked the ohms on the stock coils and all seems well , I will probably order one coils and put those in

 

[JasonH]

Try again with Motorcraft coils. If you have Motorcraft and aftermarket, make sure you mark them and see if the issue is following a particular coil. Also make sure your air filter is free of obstructions. I had one of those blue shop towel get sucked into the filter box once. Kept getting a misfire during heavy throttle.

 

[krzstruyk]

Try again with Motorcraft coils. If you have Motorcraft and aftermarket, make sure you mark them and see if the issue is following a particular coil. Also make sure your air filter is free of obstructions. I had one of those blue shop towel get sucked into the filter box once. Kept getting a misfire during heavy throttle.

I’ll give it a shot , are these motors known for having bad injectors eventually or is that less likely I have about 185k on mine now

 

[LokiWolf]

Yes, it is very possible you have a bad injector at 185K.

Have you run a quality injector cleaner through? I am a big fan of Royal Purples, and it is on sale at Advance this weekend.

 

[krzstruyk]

Yes, it is very possible you have a bad injector at 185K.

Have you run a quality injector cleaner through? I am a big fan of Royal Purples, and it is on sale at Advance this weekend.

I have not , do the injector cleaners actually work ? Never done them before but I can give it a try , I’m waiting for my forscan cable to come Monday so I can do some further diagnostics

 

[JasonH]

I’ll give it a shot , are these motors known for having bad injectors eventually or is that less likely I have about 185k on mine now

I'm at 163k on my Gen 1. No injector issues. Just timing chain and turbo manifold. But I use top tier fuel so YMMV. It's not something I've heard mentioned frequently as being problematic on these engines. My misfires were plug gaps and the towel incident. I haven't even changed my coils.

Check the plug wells for oil too. The plastic valve covers leak eventually and oil will get into the well.

 

[krzstruyk]

T

I'm at 163k on my Gen 1. No injector issues. Just timing chain and turbo manifold. But I use top tier fuel so YMMV. It's not something I've heard mentioned frequently as being problematic on these engines. My misfires were plug gaps and the towel incident. I haven't even changed my coils.

Check the plug wells for oil too. The plastic valve covers leak eventually and oil will get into the well.

Than

I'm at 163k on my Gen 1. No injector issues. Just timing chain and turbo manifold. But I use top tier fuel so YMMV. It's not something I've heard mentioned frequently as being problematic on these engines. My misfires were plug gaps and the towel incident. I haven't even changed my coils.

Check the plug wells for oil too. The plastic valve covers leak eventually and oil will get into the well.

Thanks I will check it out once again today might upgrade to the recommended ngk ruthenium plugs someone else posted in another form

 

[LokiWolf]

Thanks I will check it out once again today might upgrade to the recommended ngk ruthenium plugs someone else posted in another form

I am probably the one that recommended the NGK Ruthenium plugs. The part number I recommend is typically one step colder plug also. That being said the current OEM plugs should not be causing a misfire if you are on stock tuning unloaded with good fuel and not really high ambient. Especially with 91+ in the tank. You have another issue, again, my opinion.

 

[LokiWolf]

I have not , do the injector cleaners actually work?

Yes. You should not run them often, but if you have a stuck injector it can be the difference. The brand matters.

Most people try yo use them as a solve all, and run them WAY too often. Are they worth a try once, yes.

 

[krzstruyk]

I messed with it again today move plug and coil from cyl 5 to 4 (where cyl) 5 was originally misfiring , and now it’s showing multiple misfire and cyl 4 and 5, sounds like a fueling issue to me , my forscan cable arrives tomorrow hoping to be able to diagnose this better then , is there any specific tests I should try with forscan (I’m new to this program so not sure what to try)

 

[Motorcity muscle]

Have you replaced fuel filter?

 

[tacoduck]

I will just add that I think OEM motor craft plugs manufactured after 2021 turned to crap. I changed my plugs with motor craft plugs bought from autozone (not Amazon), and started having misfire issues. Took to dealer, and they said my plug was bad(had less than 10k miles on em.)

 

[stilbo]

Re: Injectors…
Techron fuel system and injector cleaner has been my gold standard in my 5.4 and 3.5 Expeditions for nearly twenty years.
The 2003 5.4 went 262,000 miles and ran great other than spitting out three spark plugs (Staked inserts) and new Motorcraft coils, when I traded it in for the 2015.
It was a total Northern Indiana rust bucket but ran great.
The 2015 only has 132,000 miles on it with no problems so far.

 

[Andrew Roth]

Sounds funny, but stick a flashlight up the tailpipe and look for insulation. My muffler came apart internally and plugged the tailpipe with the fiberglass insulation and caused a misfire on cylinder #6. This happened to me while towing our RV. Looked like a dead animal was stuck in the exhaust pipe.