Horrible engine shake
Thread Starter
Junior Member
Joined: Oct 2015
Posts: 7
Likes: 1
Horrible engine shake
So my 5.4 07 f150 started running weird. At idle, the engine shakes a lil. Not bad. As I accelerate its about the same until I hit 40 mph and it's like driving on a washboard.. Then as soon as I let off the gas pedal it goes away? I haven't pushed it over 40.. But also when I hit 40 the check engine light flashes, under 40 it's a solid light. Thoughts?
LightningRod
Joined: Jan 2014
Posts: 2,412
Likes: 651
From: San Antonio Texas
@MyNightmareFord
You can get a "Snap" diagnosis from "Snap Chat". Here, you deserve more. The "washboard" sensation you describe is likely the result of a designed follow on condition of the flashing CEL. To be precious, a flashing CEL indicates a catalyst damaging condition exists - (not specifically a mis-fire condition). If that condition presists longer than a factory determined time, the PCM enforces a "self preservation" mode or sometimes referred to as a "limp" mode and shuts down injectors on alternating cylinders trying to save itself from damage. When that hits - it does cause a TERRIBLE shake.
While it is true that mis-fires can cause flashing CEL by excessive unburned fuel reaching the CATS, other things can too. Such as leaky or sticking injectors or bad O2 sensors. Leaky injectors will ALSO exhibit poor idle condition. That or a defective upstream O2 would, depending on how aggressive you are accelerating - cause the PCM to be going OUT OF closed loop around 40 and revert to default injector pusle widths (much richer than short term trims if its conpensating for an over-rich injector OR an over-active O2).
You didn't mention any codes or mileage on present plugs or last service. But LaMartian's advice is sound. Pull some codes AND freeze frame data. If fuel trims are not elevated and O2 readings are within spec, the PCM maintains a TON of data captured at the time of the last misfire. Such as: Total Number of Misfires; Engine RPM at time of Misfire; Engine Load at time of Misfire; Vehicle Speed at time of Misfire; Intake Air Temp at the time of Misfire; Engine Running Time at time of Misfire - to name a few. If you have access to a code reader that can read Extended PIDs, I can provide you the numbers for these PID fields.
Meanwhile, grab some injector cleaner and heed the advice of @lewissa81 - and take care of it before the unburned gas destroys your cats. It is undisputable "you probably need a good tune up", and it is probably your spark plugs as @techrep says, but I prefer the more analytical approach coupled with all the knowledge I can get my hands on before making a definite diagnosis.
You can get a "Snap" diagnosis from "Snap Chat". Here, you deserve more. The "washboard" sensation you describe is likely the result of a designed follow on condition of the flashing CEL. To be precious, a flashing CEL indicates a catalyst damaging condition exists - (not specifically a mis-fire condition). If that condition presists longer than a factory determined time, the PCM enforces a "self preservation" mode or sometimes referred to as a "limp" mode and shuts down injectors on alternating cylinders trying to save itself from damage. When that hits - it does cause a TERRIBLE shake.
While it is true that mis-fires can cause flashing CEL by excessive unburned fuel reaching the CATS, other things can too. Such as leaky or sticking injectors or bad O2 sensors. Leaky injectors will ALSO exhibit poor idle condition. That or a defective upstream O2 would, depending on how aggressive you are accelerating - cause the PCM to be going OUT OF closed loop around 40 and revert to default injector pusle widths (much richer than short term trims if its conpensating for an over-rich injector OR an over-active O2).
You didn't mention any codes or mileage on present plugs or last service. But LaMartian's advice is sound. Pull some codes AND freeze frame data. If fuel trims are not elevated and O2 readings are within spec, the PCM maintains a TON of data captured at the time of the last misfire. Such as: Total Number of Misfires; Engine RPM at time of Misfire; Engine Load at time of Misfire; Vehicle Speed at time of Misfire; Intake Air Temp at the time of Misfire; Engine Running Time at time of Misfire - to name a few. If you have access to a code reader that can read Extended PIDs, I can provide you the numbers for these PID fields.
Meanwhile, grab some injector cleaner and heed the advice of @lewissa81 - and take care of it before the unburned gas destroys your cats. It is undisputable "you probably need a good tune up", and it is probably your spark plugs as @techrep says, but I prefer the more analytical approach coupled with all the knowledge I can get my hands on before making a definite diagnosis.
Thread Starter
Junior Member
Joined: Oct 2015
Posts: 7
Likes: 1
@MyNightmareFord
You can get a "Snap" diagnosis from "Snap Chat". Here, you deserve more. The "washboard" sensation you describe is likely the result of a designed follow on condition of the flashing CEL. To be precious, a flashing CEL indicates a catalyst damaging condition exists - (not specifically a mis-fire condition). If that condition presists longer than a factory determined time, the PCM enforces a "self preservation" mode or sometimes referred to as a "limp" mode and shuts down injectors on alternating cylinders trying to save itself from damage. When that hits - it does cause a TERRIBLE shake.
While it is true that mis-fires can cause flashing CEL by excessive unburned fuel reaching the CATS, other things can too. Such as leaky or sticking injectors or bad O2 sensors. Leaky injectors will ALSO exhibit poor idle condition. That or a defective upstream O2 would, depending on how aggressive you are accelerating - cause the PCM to be going OUT OF closed loop around 40 and revert to default injector pusle widths (much richer than short term trims if its conpensating for an over-rich injector OR an over-active O2).
You didn't mention any codes or mileage on present plugs or last service. But LaMartian's advice is sound. Pull some codes AND freeze frame data. If fuel trims are not elevated and O2 readings are within spec, the PCM maintains a TON of data captured at the time of the last misfire. Such as: Total Number of Misfires; Engine RPM at time of Misfire; Engine Load at time of Misfire; Vehicle Speed at time of Misfire; Intake Air Temp at the time of Misfire; Engine Running Time at time of Misfire - to name a few. If you have access to a code reader that can read Extended PIDs, I can provide you the numbers for these PID fields.
Meanwhile, grab some injector cleaner and heed the advice of @lewissa81 - and take care of it before the unburned gas destroys your cats. It is undisputable "you probably need a good tune up", and it is probably your spark plugs as @techrep says, but I prefer the more analytical approach coupled with all the knowledge I can get my hands on before making a definite diagnosis.
You can get a "Snap" diagnosis from "Snap Chat". Here, you deserve more. The "washboard" sensation you describe is likely the result of a designed follow on condition of the flashing CEL. To be precious, a flashing CEL indicates a catalyst damaging condition exists - (not specifically a mis-fire condition). If that condition presists longer than a factory determined time, the PCM enforces a "self preservation" mode or sometimes referred to as a "limp" mode and shuts down injectors on alternating cylinders trying to save itself from damage. When that hits - it does cause a TERRIBLE shake.
While it is true that mis-fires can cause flashing CEL by excessive unburned fuel reaching the CATS, other things can too. Such as leaky or sticking injectors or bad O2 sensors. Leaky injectors will ALSO exhibit poor idle condition. That or a defective upstream O2 would, depending on how aggressive you are accelerating - cause the PCM to be going OUT OF closed loop around 40 and revert to default injector pusle widths (much richer than short term trims if its conpensating for an over-rich injector OR an over-active O2).
You didn't mention any codes or mileage on present plugs or last service. But LaMartian's advice is sound. Pull some codes AND freeze frame data. If fuel trims are not elevated and O2 readings are within spec, the PCM maintains a TON of data captured at the time of the last misfire. Such as: Total Number of Misfires; Engine RPM at time of Misfire; Engine Load at time of Misfire; Vehicle Speed at time of Misfire; Intake Air Temp at the time of Misfire; Engine Running Time at time of Misfire - to name a few. If you have access to a code reader that can read Extended PIDs, I can provide you the numbers for these PID fields.
Meanwhile, grab some injector cleaner and heed the advice of @lewissa81 - and take care of it before the unburned gas destroys your cats. It is undisputable "you probably need a good tune up", and it is probably your spark plugs as @techrep says, but I prefer the more analytical approach coupled with all the knowledge I can get my hands on before making a definite diagnosis.
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LightningRod
Joined: Jan 2014
Posts: 2,412
Likes: 651
From: San Antonio Texas
Hey @techrep
On re-reading my attempt to be funny in post #5, a very real (but unintended) interpretation struck me that could justifiably have be taken as offensive by you - for which I wish to apologize. I was not belittling your advice or that of other members ahead of me. In my defense, I did say "it is probably your spark plugs as @techrep says".
I had just noticed it was the OP's first post - on his registration day. His brief profile and with no other posts to review, I was clueless about his truck's history and I didn't want him to feel his question was glossed over. I did sense some degree of a rush to judgment that could have potentially sent the OP off on a rabbit trail. But at the time, the snap chat analogy struck me funny. Today (in context of his reply and other posts) it stuck me as smart assed. It wasn't intended that way.
On re-reading my attempt to be funny in post #5, a very real (but unintended) interpretation struck me that could justifiably have be taken as offensive by you - for which I wish to apologize. I was not belittling your advice or that of other members ahead of me. In my defense, I did say "it is probably your spark plugs as @techrep says".
I had just noticed it was the OP's first post - on his registration day. His brief profile and with no other posts to review, I was clueless about his truck's history and I didn't want him to feel his question was glossed over. I did sense some degree of a rush to judgment that could have potentially sent the OP off on a rabbit trail. But at the time, the snap chat analogy struck me funny. Today (in context of his reply and other posts) it stuck me as smart assed. It wasn't intended that way.