Low RPM, Low Load Shudder and Misfire

[Cheez_Greater]

Last week my 2021 F-150 3.5L with about 33K developed a fairly hard shudder under low RPM cruising when a light amount of load is added, like accelerating slightly or going up a small rise. The shudder will continue unless you increase the throttle and it shifts down or manually shift down. Twice I've received a notification from FordPass that a misfire has occurred, but no check engine light and no DTCs when I check with Forescan. I do have a catch can which has been installed for about a year. I'm going to take that out and see if that makes a difference, like the catch can system has developed a vacuum leak. I just want to eliminate a variable. Has anybody else had a similar misfire issue?

Sponsored

 

[Bryan Simon]

Can’t really answer this for you but I wonder if if you are getting the automatic trans version of the manual trans “gear rattle”.

hear me out.
I have a 98 Chev K1500 with many many miles on it (love this workhorse)
5.7 and a manual 5spd
Previous engine and the current engine did the same thing.
I have a few small grade and low speed areas in my area that would be better suited for a gear between 2nd 3rd.
Trans will rattle a bit, knock sensors take over and rapidly mess with ignition timing and on top of that, every few seconds the engine will misfire (no misfire codes).
I think it’s a misfire but may be all the ignition computer crap just messing with timing really fast
Not sure.

At any rate, what you describe, and how I interpreted, seems to me to the modern day “gear rattle” and maybe the trans needs to be flashed for better shift points.

You buy this new??

 

[Cheez_Greater]

Can’t really answer this for you but I wonder if if you are getting the automatic trans version of the manual trans “gear rattle”.

hear me out.
I have a 98 Chev K1500 with many many miles on it (love this workhorse)
5.7 and a manual 5spd
Previous engine and the current engine did the same thing.
I have a few small grade and low speed areas in my area that would be better suited for a gear between 2nd 3rd.
Trans will rattle a bit, knock sensors take over and rapidly mess with ignition timing and on top of that, every few seconds the engine will misfire (no misfire codes).
I think it’s a misfire but may be all the ignition computer crap just messing with timing really fast
Not sure.

At any rate, what you describe, and how I interpreted, seems to me to the modern day “gear rattle” and maybe the trans needs to be flashed for better shift points.

You buy this new??

I agree that it does feel like gear rattle. I reset the transmission adaptive tables to see if that makes a difference. I looked at live fuel trim data while driving and it looks fine so probably no vacuum leak. I did buy it new and it has an appointment at the dealer. Hopefully I fixed it though.

 

[Oxford_Powerboost]

I think ecoboosts are known to be pretty hard on plugs - it could have opened up the gap on a plug just enough to start misfiring. Additionally, I’ve seen coil packs be a somewhat common problem on 14th gen f150s.

 

[Cheez_Greater]

So the truck is heading to the dealership tomorrow... I reset the transmission adaptive tables, removed a catch can, updated the PCM via FDRS, and after each thing the shudder and FordPass misfire notification occured. A couple days ago the shudder even occured while stopped at a light at idle in drive. After the idle shudder, while driving at 35 at low RPM, the truck shuddered like I was driving on washboard. Then I actually saw the check engine light flash, until the truck ran smooth again after about 10 seconds, then the light turned off. FordPass then alerted a misfire. The issue is really intermittent but hopefully the techs can figure it out.

 

[dberner20]

I have a 2016 that has started to have the same issue. Strong vibration in dash, not in steering wheel, or seat. Usually happens on highway in 6th gear and about 5lbs of boost. When truck drives up a slight hill and there is more load on engine. Vibration goes away when I let off gas or if I give more gas and increase rpms. This is the only thread i can find with this issue. Let me know what you find out.

 

[Cheez_Greater]

I did a Mode 6 test and looked at misfires. I am seeing last drive misfires of 1 or 2 for all cylinders except 4. No EWMA misfires for last 10 drive cycles for any cylinders except number 2. That cylinder has 14 which doesn't sound good.

 

[Cheez_Greater]

So after some time at the dealer, the running thought is the transmission is having issues. The fluid looks pretty burnt and the dealer is working with Ford to see how they want to deal with it. Fun times.

 

[Ford Motor Company]

So after some time at the dealer, the running thought is the transmission is having issues. The fluid looks pretty burnt and the dealer is working with Ford to see how they want to deal with it. Fun times.

Hi there, Jason. These transmission concerns doesn’t sound like something we want you to experience with your truck. Could you please send us a PM with your VIN and the name and location of your Ford dealer? To send a private message, just click on our username and select "Start Conversation". I'd be happy to look into how I can assist you on my end.

 

[WhiteLightningnshitshadow]

So after some time at the dealer, the running thought is the transmission is having issues. The fluid looks pretty burnt and the dealer is working with Ford to see how they want to deal with it. Fun times.

Anything come of this?

Im surprised to see the trans issue in conjunction with a coil/plug issue. Im pretty interested as I have an issue where 9 and 10 are causing misfires when the egr kicks in.

 

[Cheez_Greater]

I haven't had the shudder issue since Iast posted, which is odd. I am bringing the truck in tomorrow so the dealer can perform some tests regarding the dark trans fluid issue. I'll post what the result of that is. I swear the gas mileage has dropped a bit since this issue started but I can't be totally sure. I drive like I'm driving Miss Daisy, my wife.. not so much.

 

[Cheez_Greater]

Update. The dealership did an advanced break in that cycled the transmission valve body many times. The dealer, I guess, thought the misfire code was being triggered from the transmission hesitating. Now as of yesterday I'm finally getting misfire codes instead of just FordPass messages saying I had a misfire. There are codes for a cylinder 2 misfire and a cylinder 2 misfire in the first 1000 revolutions. I made sure and saved the codes and mode 6 test results in ForSCAN in case the codes clear out automatically. It goes in Monday to check the codes. The misfire was really bad yesterday and I could feel a dead cylinder while idling at a stoplight. The misfire is intermittent still but at least the tech has codes to go on.

 

[Cheez_Greater]

So after a few hours at the dealer yesterday, the said they followed a TSB and applied some dielectric lube to the coil boots. Hopefully that fixed the issue.

 

[Cheez_Greater]

So a couple weeks ago the misfire came back and moved to cylinder 1. The dealer did their due diligence and replaced a bad coil and sparkplug. So to recap.
1. FordPass reports misfire
2. Dealer can't see an issue (why does FordPass report a misfire but no code, that's dumb).
3. Dealer sees potential problem in transmission, does, things to it.
4. Misfire is back, TSB says, just add grease
5. Misfire is back, weird that just add grease doesn't fix the issue.
6. Actually replace the defective parts.

For those keeping track, that's 4 visits and a total of about 7 days in the shop, for a bad coil and plugs. If a code would have been tripped in the PCM, that would have saved a ton of my time and Ford's money.

EDIT: I should say that I think the misfire moved from cylinder 2 to 1 because when the dealer added the grease, they proactively moved the coil to help diagnose the misfire

 

[WhiteLightningnshitshadow]

Ford's diagnostics and condition recording is so close yet so far.

Sponsored