Shudder / Shaking Misfire Under Load - not spark plugs

GJarrett · Feb 7, 2018

BTW Thanks Kevin for checking in. I reviewed your other thread here and wonder if I may be having fuel starvation and/or wastegate issues, only at a different rpm/load than yours.... it might be something for me to tell my service mgr to go chase down.

ElAviator72 · Feb 7, 2018

Wow, all this talk about condensation in the intercooler has got me thinking. I'm 100% stock. What kind of conditions (in general) would be required to create condensation in the intercooler? I know about relative humidity, dew point, atmospheric pressure, etc. Just wondering if the stock tune takes these things into consideration to try and keep the engine out of the region that would be prime for intercooler condensation?

GJarrett · Feb 7, 2018

Well I am not sure condensation could be it, just trying to hunt down possibilities... let me take mine off first and I'll let ya know if it had any moisture in it. The condensation issue, as far as I can tell, was on early model F150 3.5 v6 Ecoboosts, and seems to not be an issue in later years so maybe Ford changed the design for that one. I've actually never heard of any of our Mustangs having it yet, and if that's not my problem, then I am confident it is a non-issue for our S550 models.

TEXAS HEAT · Feb 8, 2018

GJarrett said:
FP tune, catch can, cp-e intercooler. Check my sig line for full list of mods.

At 27k miles my EB started a severe shudder/shaking in 6th gear when accelerated uphill from low rpms. I can cruise at 55-60mph in 6th gear, then floor the go pedal, and the whole vehicle will shudder until it speeds up to a higher rpm when it will smooth out. The whole vehicle will shake, initially feeling almost like an out-of-balance driveshaft or bad u-joint or something. It is NOT the 50-70 mph vibration problem. It only happens under load - I can get it to do it in 5th gear too it's just a lot more significant in 6th - it does not happen at high rpms or when it is coasting. If I wind out the engine without lugging it, it purrs like it's supposed to.

No CEL and no codes thrown.

BTW, I KNOW I'm not supposed to lug the engine but something is wrong and it needs fixed.

I took it to my dealer's service department and they too felt like it was a driveline issue, they called the regional Ford engineer and his long-distance diagnosis said it was the 50-70 mph vibration, but he didn't ride in it and I knew this was different.

I asked them to scan it (just in case) in order to cross off as many possible options before throwing parts at this problem. The service mgr agreed and wanted to do what he called a Mode 6 scan while riding with me and watch the engine on his computer.

The scan tool would not recognize the car because I had the FP tune installed, so I went home and reflashed the car back to stock tune and filled up with 87 octane. I immediately noticed the shudder was not nearly as bad with the lowered power but it was still definitely there and at reduced severity I could tell that it seemed to originate up front of the car. My hopes rose that it was in the engine and would be something they could scan and identify.

Yes and no. The scan tool recognized my Mustang, we went for a ride with the service mgr in the passenger seat looking at his computer while I hit the gas at low rpm going uphill in 6th gear. Bingo, all four cylinders showed misfires until we sped up to higher rpms and it smoothed out again. So it's not driveline related after all.

I am familiar with the spark plug threads here so my first thought was plugs. I buy a set, go home, and pull my plugs. They looked fine, gaps are all good, but just to make sure I replace them with new plugs. The problem is still there. My service manager is stumped and it looks like he wants to keep it awhile to study it. I'd prefer my car has a short stay to get a known problem fixed quickly, not leave it at the dealer for who knows how long.

So it's not a coil or a plug, it's something that affects all of them. In digging through searches I found what may be a similar problem with F150 EBs having a condensation problem in their intercoolers. The intercoolers work so well that in humid conditions they condensate water that gets sucked in the intake to cause the shuddering. The fix seems to be drilling a small 1/8" "weep hole" in the bottom of the intercooler to let oil/condensation water out. Has anyone heard of this in our Mustangs? I really don't want to drill a hole in my intercooler.... or would it do no harm, so what-the-heck give it a try?

Does anyone have any possible ideas what the problem could be, or helpful suggestions where to start looking?

Sounds like LSPI, aka super knock. Low engine speeds and high load demands (5th and 6th gear) acceleration runs are in the LSPI range where you are experiencing the issue. If you're demanding a significant amount of boost at low RPM, of course it's going to buck. Even if you have good quality high octane fuel, it can still occur.

Here's a few links about LSPI and what to do to prevent it. Biggest cause is lugging the engine.

http://stratifiedauto.com/blog/low-...the-mazdaspeed-disi-and-ford-ecoboost-motors/

https://www.oronite.com/products/lspi.asp

GJarrett · Feb 9, 2018

Thanks for the input. I thought about LSPI also but have discounted it because (1) it never happened before, thinking it would be a condition that either is or isn't, instead of just showing up all of a sudden 27k miles down the road, (2) I've only heard about LSPI in reference to blown engines, and mine's not blown, and (3) it shudders so hard that if it was LSPI, I would think it would grenade the rods. As a matter of fact I've been lugging it on purpose lately to try to break whatever is going on so we can figure it out before my warranty is up

All that being said, I admit it could be some version of LSPI.

One other possibility brought up by one of the techs was that he has seen a harmonic balancer go bad, and when it started shaking the engine, it caused misfires when the computer tried to correct for the imbalance.

We took another test drive with it hooked up to the diagnostic computer. Fuel flow and evap are both good and he kept the recording of the driving session, it misfired 21 times. He is going to send the file to Ford and discuss on the phone to see if they can provide any help.

Apple · Feb 9, 2018

I started my account because of this thread. That's an interesting problem you're having, I have been experiencing something similar. I also have a similar setup with the FP tune, mishimoto intercooler (waiting on the street series cat back) but an automatic transmission.

The AT transmission with 3.31 gears likes to keep the engine speed around 1500rpm's in D mode at all times, regardless of gear and speed. When I accelerate from this range, and I'm talking with as little as 1/8th of pedal travel, there is a complete lack of response with a shuddering and vibration that feels similar to a manual car about to stall the engine. Gradually apply more throttle and the AT finally figures out how to downshift, and then away it goes smoothly.

I've noticed a couple things. The problems appears exaggerated after having installed the FP tune and intercooler, which I'll note I installed at the same time. Strangely, the issue doesn't occur within several minutes after first starting the car in the morning, up until both oil and transmission temps rise.(-5*F outside) RPM's rise smoothly with pedal travel, in the same gear. This lead me to believe that maybe something is changing after the computer switches from open to closed loop operation, but it is also entirely possible that there is intercooler ice melting. The fact that you were seeing several misfires has me more concerned. Does it only occur within a certain RPM range?

When I drive around in sport mode I have zero response issues at all, but I am also realizing that I drive the car above that RPM range. Later today I'll test sport mode in those lower RPM's.

TEXAS HEAT · Feb 9, 2018

GJarrett said:
Thanks for the input. I thought about LSPI also but have discounted it because (1) it never happened before, thinking it would be a condition that either is or isn't, instead of just showing up all of a sudden 27k miles down the road, (2) I've only heard about LSPI in reference to blown engines, and mine's not blown, and (3) it shudders so hard that if it was LSPI, I would think it would grenade the rods. As a matter of fact I've been lugging it on purpose lately to try to break whatever is going on so we can figure it out before my warranty is up

All that being said, I admit it could be some version of LSPI.

One other possibility brought up by one of the techs was that he has seen a harmonic balancer go bad, and when it started shaking the engine, it caused misfires when the computer tried to correct for the imbalance.

We took another test drive with it hooked up to the diagnostic computer. Fuel flow and evap are both good and he kept the recording of the driving session, it misfired 21 times. He is going to send the file to Ford and discuss on the phone to see if they can provide any help.

Misfires can and do occur, but if it doesn't throw a code, everything is considered normal from the ecu stand point. What I found interesting is the tech mentioned a pulley that was out of balance and this made me think about the tensioner. There have been a few of those that have failed and caused the same type of symptoms. You may want to check that as well.

GJarrett · Feb 9, 2018

Apple, your problem does sound similar. The area I live in does not have anywhere near the low temperatures you do so I can't speak to that; mine always does it - but I don't drive in subzero weather either. The FP tune does make it worse. When I reflashed back to stock tune it lessened, but I believe that's simply a result of losing 70 lb-ft of torque so it's not kicking the misfire so hard, not that it causes/changes anything about the problem.

Texas Heat I would never have thought of a tensioner causing something like this, thanks for providing another avenue to look at.

Turbong · Feb 9, 2018

How would one diagnose a "bad" pensioner?

ElAviator72 · Feb 9, 2018

Turbong said:
How would one diagnose a "bad" pensioner?

Wouldn't that be a cranky old guy in England who kicks kids and pets out of his front garden? :lol:

ElAviator72 · Feb 9, 2018

TEXAS HEAT said:
Misfires can and do occur, but if it doesn't throw a code, everything is considered normal from the ecu stand point. What I found interesting is the tech mentioned a pulley that was out of balance and this made me think about the tensioner. There have been a few of those that have failed and caused the same type of symptoms. You may want to check that as well.

Might be worth a try in my case, it seems as if it started after I had it in to the dealer in late Oct. for, amongst other things, repairing an oil leak that was happening in the front timing chain area (they had to take the whole front end of the engine apart, it ended up being the timing chain gasket). I'm wondering if it is possible that the pulley tensioner got messed up in the process...

Apple · Feb 9, 2018

GJarrett said:
Apple, your problem does sound similar. The area I live in does not have anywhere near the low temperatures you do so I can't speak to that; mine always does it - but I don't drive in subzero weather either. The FP tune does make it worse. When I reflashed back to stock tune it lessened, but I believe that's simply a result of losing 70 lb-ft of torque so it's not kicking the misfire so hard, not that it causes/changes anything about the problem.

Texas Heat I would never have thought of a tensioner causing something like this, thanks for providing another avenue to look at.

I wonder if profile learning in the Procal software could make a difference.
from the instruction pdf:

The Profile Learning switch should only be switched to “ON” when the engine is reporting a misfire DTC such as P0300-P0316. By enabling this switch, the engine will prompt the driver to rev the engine to a specific rpm until the PCM relearns the fire pattern characteristics of the trigger wheel.

Also while driving today, I experimented with every driving mode on the transmission. The problem consistently occurs in any mode while in 3rd gear or above, and while between 1250 and 1600 rpm.

Edkiefer · Feb 9, 2018

That's a real odd issue, misfire to the point of losing power (all cylinders affected) but not throwing a code.
Since its all 4 I would first check things like all grounds arre tight, motor mounts not cracked.
Then maybe check timing, "maybe" if crank bolt loosened it moved timing a bit but not enough to throw code (reaching there).
Its hard to diagnosis over internet, but if you could find a way to reproduce while car is standing still you could probably pin it down fast.

GJarrett · Feb 10, 2018

Apple said:
I wonder if profile learning in the Procal software could make a difference.
from the instruction pdf:

The Profile Learning switch should only be switched to “ON” when the engine is reporting a misfire DTC such as P0300-P0316. By enabling this switch, the engine will prompt the driver to rev the engine to a specific rpm until the PCM relearns the fire pattern characteristics of the trigger wheel.

Also while driving today, I experimented with every driving mode on the transmission. The problem consistently occurs in any mode while in 3rd gear or above, and while between 1250 and 1600 rpm.

I've already reflashed back to stock tune.... I wonder if Procal could fix it by enabling that switch (?)

I suppose I have nothing to lose by trying it... today I'll disconnect my negative cable awhile to let the car reset, then hook up ProCal and turn that switch on. Can't hurt anything by trying, thanks for the idea.

TEXAS HEAT · Feb 12, 2018

GJarrett said:
I've already reflashed back to stock tune.... I wonder if Procal could fix it by enabling that switch (?)

I suppose I have nothing to lose by trying it... today I'll disconnect my negative cable awhile to let the car reset, then hook up ProCal and turn that switch on. Can't hurt anything by trying, thanks for the idea.

The FRPP tune file does have a couple of different options when you download the software. One is to have the spark relearn feature and is definitely worth a try. As far as the tensioner, if it's the bearing it is usually noisy and will visibly bounce around while at idle and sometimes will sqeek, especially on cold starts. That little bouncing at idle will only become worse as the engine load increases. I'm not saying for sure if this is your problem, but something to check anyway. What are your plugs gapped at btw?

Shudder / Shaking Misfire Under Load - not spark plugs

GJarrett

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ElAviator72

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GJarrett

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TEXAS HEAT

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Apple

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TEXAS HEAT

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Turbong

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