What is making my Ranger jerk and shake intermittantly? - Ranger-Forums - The Ultimate Ford Ranger Resource


4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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Old 06-17-2015
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What is making my Ranger jerk and shake intermittantly?

Hi; I have owned this 2009 Ranger Sport 4x4 with now 70K mi for a little over a year. i've placed approx. 12K on it. Up till approx. 2mo. ago it has driven flawless but now i have developed a very strange problem that has left 2 technitions sctratching their heads to resolve. I have this intermittant sudden "Shake' or "Faltering" that occurs somewhere in the drivetrain(either engine or further back) that occasionally occurs. Under the most severe occurrence the whole chassis will shake as if I have been driving over railroad ties, other times its more subtle. Been going on approx. 2 mo. but up till the other day the check engine light had not come on. Once it finally did, it indicated 'A misfire" in #3 cyl. Prior to the check engine illuminating I had this at a Ford dealership who could not reproduce the problem during limited drive time and sent me home!
Subsequently I drove it with my trusted mechanic for approx. 5 mi. and could not reproduce the problem however it continues to happen intermittently yet rather unpredictably. If there is a pattern to it then it may occur during light acceleration at lower slower speeds and more frequently traveling up long grades however it may happen under any situation and speed does not seem to be relevant except to say that it appears to occur mostly when in a higher gear/lower RPM. I'm telling you that the severeness ranges from subtle to almost seismic scale and the whole chassis will shudder(not to be confused with a failing torque converter). We have replaced the ignition coil/plugs and wires out of "likely culprits" logic. Except when this problem occurs the Ranger drives normally. I'm beginning to think this out along other possible issues e.g. vacuum/tranny, U-jt. or differential slipping even perhaps a slipping timing belt? Please advise or ask for a more detailed description if you care to enter my world and thx. Bill D.
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Old 06-17-2015
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shake or faltering indicates to me that what you are experiencing is actually fuel PRE-IGNITION

what octane of fuel are you burning in your engine presently , if it is 87 octane that may be the culprit

try running 2 tanks of ESSO 91 octane fuel ( there are NO cleaners or additives or ethanol in that octane of fuel )

to see if the problem occurs still ( it might just be the fuel that is causing the problem )
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Old 06-17-2015
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Yes, +1 ^^^

4.0l SOHC engine has a Knock sensor under the intake manifold, these do fail.
This engine has 9.7:1 compression ratio so "they" had to add a knock sensor because it WILL ping/knock(pre-ignition) on 87 octane.
The knock sensor detects the pre-ignition(before you can hear it) and the computer retards the spark timing so spark plug ignites fuel before it can self ignite.
This represents a loss of power and if knock sensor was intermittent it could fit those symptoms.
These are a PITA to replace, lol.

Clean the MAF sensor, dirty MAF sensor will cause "bucking", which sounds similar to your description.

Long shot is TPS(throttle position sensor), this sensor tells the computer if gas pedal is being used and in what position it is in.
This sensor works like a light dimmer or volume control a simple rheostat(variable resistor)
Computer sends it 5 volts
TPS send back under 1 volt if your foot is off the gas
TPS sends back above 4.5 volts if gas pedal is pushed down to the floor.
So gas pedal at 1/2 way might be 2. 15 volts, 3/4 3.5 volts, ect....
Now if there was a worn spot on the TPS, the volt might suddenly drop, so computer thinks you took your foot off the gas, then voltage jumps back up where it should be so you get a "bucking" in the vehicle like you where pumping gas pedal only a faster response.
TPS is easy to test with volt or ohm meter, they rarely fail, but rarely is not never, lol, long shot but not a no shot.

9 out of 10 sensors, or controls, replaced by DIYers were not broken, so never replace anything without testing it.
And just FYI, 6 out of 10 sensors replaced by professional mechanics were not broken, lol, but I think some of that is just padding the bill.

Last edited by RonD; 06-17-2015 at 10:13 PM.
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