Final Attempt - Misfire Issue

[Mike Pfeifer]

I wanna know how they determined the spark plugs and the coils were good. Did they just look at them and determine they were goodor did they do an ohm’s test. Because neither one of these are a very good way to test if these parts aregood under a load.

I think the spark plugs and ignition coils have already been purchased, if I am remembering correctly. So the money is already spent. Can’t hurt to replace them just to see if there is any change in behavior. It seems like such a low hanging fruit.

Sponsored

 

[Evenmetal]

Check your ti-vct solenoid harness's. If faulty, they can cause rough idle or even a misfire. Easy fix though.

 

[phatsesh]

So for what it’s worth I have a 2017 GT, for the past 9 years of owning this vehicle I’ve had an intermittent P300 code pop-up during hard driving. I’ve taken it to the dealership while under warranty and they would tell me things like change the plugs change your packs whatever the code would disappear and then under certain hard driving experiences, it would reoccur. Finally this past December I got a flashing check engine light with 300 and 308. My father has his own shop. I took it to his shop and ran the diagnostics myself I tested compression and It was slightly lower than the rest of the cylinders remove the engine, took the heads off, expecting some valves damage and saw damage in cylinder seven and eight, proceeded to remove the pistons and found that they were cracked in between the rings and caused marring to the cylinders. I suspect the pistons have been damaged for sometime and just finally reached the point where the mis fires were consistent.

 

[GregO]

Overview of misfire issue
The car only has a random misfire during heavy load (typically happens in 2nd gear WOT uphill). I sometimes hear a strange noise coming from the exhaust of the car and starts around 6K rpms in second gear.

I have to jump in and share a story. Admittedly I haven’t read all the posts 100% so take this with a grain of salt.
A few decades ago a good buddy had a GSXR 1100 with a strange but very isolated miss, could feel and hear it only under certain running condition. Typically under heavy power and at a certain speed/RPM. This was before advance ECU/PCM management. We did the typical ignition checks and engine mechanical inspection.
After we burned all the hair off our heads we discovered it was either 2nd or 3rd gear ( I can’t remember which) that was missing a few teeth. Replaced the gear and issue solved.
End of Story.

 

[gilbenja]

I have to jump in and share a story. Admittedly I haven’t read all the posts 100% so take this with a grain of salt.
A few decades ago a good buddy had a GSXR 1100 with a strange but very isolated miss, could feel and hear it only under certain running condition. Typically under heavy power and at a certain speed/RPM. This was before advance ECU/PCM management. We did the typical ignition checks and engine mechanical inspection.
After we burned all the hair off our heads we discovered it was either 2nd or 3rd gear ( I can’t remember which) that was missing a few teeth. Replaced the gear and issue solved.
End of Story.

This is essentially what the mechanic at upland ford was saying. He thinks some of the teeth are broken and the metal shavings is throwing off a sensor.

However, people in this forum disagree since I can still drive the car fine and put the car into 2nd and 3rd gear.

 

[GregO]

I can still drive the car fine and put the car into 2nd and 3rd gear.

Could be your synchros are not totally ragged out yet.
I’m of the opinion that if this is a case of missing gear teeth your crankshaft position sensor would pick up the inertia disruption under load. Steady state cruising is a different situation for obvious reasons.

 

[sk47]

However, people in this forum disagree since I can still drive the car fine and put the car into 2nd and 3rd gear.

Hello; i cannot recall how long it has been since you posted the first of the three threads i know of. Been weeks anyway. I am not positive but think you have been to three shops and have had in person rides with maybe two mechanics. Lots of suggestions from the threads posted on here.
A thing is at some point you will have to "bite the bullet" and tear into the engine and/or transmission. You can do more baby steps as you already have done, but I figure such will give hints and not conclusions.
Metal shaving in a transmission is simple to check. For an automatic drop the pan and such will be easy to see. For a manual drain the trans oil into a very clean pan and look.

from the first post back in thread #1 you have scored cylinders & a misfire code. One or two mechanics say the transmission grinds (I suspect a manual)

That you can still drive the car and change gears sounds like wishful thinking. But that said, sounds like you are still driving it. if parts are failing you will eventually get to the point of clear signs. The only reason to not drive the car back weeks ago was to have a chance to salvage some parts and stop further damage. From what i have read you drove to high RPM's with a mechanic or two and the mechanics were concerned.
I still wish you luck with the car, but I do not understand.

 

[gilbenja]

Hello; i cannot recall how long it has been since you posted the first of the three threads i know of. Been weeks anyway. I am not positive but think you have been to three shops and have had in person rides with maybe two mechanics. Lots of suggestions from the threads posted on here.
A thing is at some point you will have to "bite the bullet" and tear into the engine and/or transmission. You can do more baby steps as you already have done, but I figure such will give hints and not conclusions.
Metal shaving in a transmission is simple to check. For an automatic drop the pan and such will be easy to see. For a manual drain the trans oil into a very clean pan and look.

from the first post back in thread #1 you have scored cylinders & a misfire code. One or two mechanics say the transmission grinds (I suspect a manual)

That you can still drive the car and change gears sounds like wishful thinking. But that said, sounds like you are still driving it. if parts are failing you will eventually get to the point of clear signs. The only reason to not drive the car back weeks ago was to have a chance to salvage some parts and stop further damage. From what i have read you drove to high RPM's with a mechanic or two and the mechanics were concerned.
I still wish you luck with the car, but I do not understand.

I have compiled a list of tasks for a mechanic from all of my posts.

I have called a handful of mechanics in my area, but none of them are confident in finding the misfire issue or willing to take on the project. Still trying to find someone and calling around.

Ultimately, I’m just trying to find the mechanic and get a rough estimate to perform all of the below tasks.

I’m considering either fixing the car, or just selling it and buying a mach 1. It will just depend on how much it costs for the repairs.

1. check crank sensor and tone ring 2. check wiring harness and pigtails for faulty connection
3. fuel trims and rail pressure (HPFP pressure (desired vs actual), LPFP pressure, Injector pulse width, STFT/LTFT at WOT, MAF counts, Knock retard, Cylinder contribution test
4. log fuel pressure under heavy load since car only misfires then
5. check transmission fluid to rule out if the tranny is broken
6. checked all of the clamps for the intake and cleaned the MAF sensor?
7. test spark plugs and coils. not just visual inspection.

 

[sk47]

I have compiled a list of tasks for a mechanic from all of my posts.

I have called a handful of mechanics in my area, but none of them are confident in finding the misfire issue or willing to take on the project. Still trying to find someone and calling around.

Ultimately, I’m just trying to find the mechanic and get a rough estimate to perform all of the below tasks.

I’m considering either fixing the car, or just selling it and buying a mach 1. It will just depend on how much it costs for the repairs.

1. check crank sensor and tone ring 2. check wiring harness and pigtails for faulty connection
3. fuel trims and rail pressure (HPFP pressure (desired vs actual), LPFP pressure, Injector pulse width, STFT/LTFT at WOT, MAF counts, Knock retard, Cylinder contribution test
4. log fuel pressure under heavy load since car only misfires then
5. check transmission fluid to rule out if the tranny is broken
6. checked all of the clamps for the intake and cleaned the MAF sensor?
7. test spark plugs and coils. not just visual inspection.

Hello Ben; I am somewhat surprised you cannot find a shop to do the work in California. But that several are not willing to take on the job sounds like a clue. For the right money shops will usually do the work. A Ford shop might want to replace the engine if you can pay. I am some curious about how the conversations go, but do not need to know.

That list is going to cost and if you decide to hire someone you will be paying again to do the job.
5. check transmission fluid to rule out if the tranny is broken
7. test spark plugs and coils. not just visual inspection.
These two tests ought to be a DIY sort of job. Especially checking the trans and or engine oil. Just drain the oil into a very clean pan and have a look.
Spark plugs and coils can be bench tested up to a point.
Most of the rest of the list may be putting off what may be the inevitable. That being an expensive tear down to the point of knowing the condition of the mechanicals.

Again, I begin to think you are hoping for a way out and I do not blame you. You bought what for many is a dream car which has started to turn into a potential nightmare. You have a car worth fixing if you can afford it. I do not know your financial situation. That you are not in a position to DIY some of the work means owning the car will be expensive to pay others for.
Can you dump the car onto some other unsuspecting person? Sure. If you do go that way at least post the VIN on here for your fellow forum members. I will understand if you wait until after the sale.
The idea of selling and getting a Mach 1 begs the question of expectations. What will prevent to next car from being trashed? Do it better and get the car checked out thoroughly before the buy. You now have an idea of what needs to be checked. Hire a mechanic to do some checks. If the seller balks, then walk away.

 

[Gen 6 Mach1]

Your scaring away any Technician, from you list and almost like they are demands , as the liability is something most shops won't want to touch . If I had the knowledge ,I wouldn't take on the project. Start back at square one and take it to the Dealership that has all the GT350 s and the Master Tech that works on them , I believe you mentioned in you other Thread . I'm not going to look back at your previous thread to see if he had his diagnosis. I feel for you, but I don't understand why you half to peg you Tach at red line, that's the only time the misfire happens.
If you drive it like a normal car , no codes , misfire. If you're going to beat the crap out of it just to get the codes, or have the engine destruct itself. If it doesn't already need replacement it's gonna .
The like half dozen Tech's you've been to all can't be incompetent . I'm Sorry , but moving around from Tech to Tech and some aren't savvy on the voodoo and misfire codes . The water is muddy and just can't see clearly thru.
Again go back to the GT350 Master Tech, I think that's you best alternative.
I do wish you the best and get to a satisfactory solution.

 

[gilbenja]

Update…

MY CAR HAS BEEN FIXED!!!

I went to GTR High Performance in Rancho Cucamonga. I finally found a mechanic, Ricardo, that was willing to actually give their time and work through the issue.

Not sure exactly what fixed the misfire as I did not do any AB testing. But here is a summary of things that was done.

1. Noticed the passenger side exhaust was loose and there was noticeable play. He fixed this.
2. Performed another crank relearn
3. Did a compression test results came back with a 10% variance… (210, 205, 210, 217, 217, 220, 220, 225)
4. Switched all spark plugs and the coil on the cylinder that gave a minor misfire
5. Checked the crank sensor
6. Borescoped the cylinders for documentation purposes to compare in the future

Thank you to everyone that helped me. Was starting to lose hope but this shop actually listened and tried to solve the problem. I recommend anyone in CA use this shop for any nuanced issues.

Still not sure whether to keep or sell the car. They did say we can monitor and if the cylinders start to show a 15%+ variance in compression, then think about selling. Their thoughts on the scoring was the same as others. Not ideal and can only get worse overtime.

As I understand, borescoping your cylinders is not a part of a routine check. How many of you have borescoped your cylinders and seen scoring similar to mine? Did the engine last for a while? Did the scoring eventually get worse?

 

[Sajin]

Not sure what oil you use, but since you have scoring you should consider switching to driven dt50, or adding two bottles of ceratec to your oil to manage the scoring.

 

[GregO]

How many of you have borescoped your cylinders and seen scoring similar to mine? Did the engine last for a while? Did the scoring eventually get worse?

Scoring ?
How are you determining the difference between cylinder scoring and normal cylinder burnishing ?

 

[Gen 6 Mach1]

What was Ricardos diagnosis? Previous diagnosis Spark plugs and coil . Replaced and all good . I'm glad all's worked out .

 

[Inthehighdesert]

Glad you got it fixed and found a competent tech. Wouldn’t worry about the cylinders.

Sponsored