Surging/jerking while accelerating???

[Ford Explorer9]

Just going to start from the beginning in chronological order.

Bought truck two months ago, repaired both exhaust manifolds right away since they were both leaking.

Diagnosed a rattle in the exhaust as the resonator.

Truck has a loss of power, 0-60 goes from 7.2 seconds to around 9 seconds. Loss tends to be most noticeable at 50% to wide open throttle.

Have resonator cut out and replaced with straight pipe and fuel filter changed. Fuel filter was almost completely plugged. (Loss of power still remains though)

On the freeway today I accelerate to wide open throttle to pass some guy doing 55 in the fast lane. During acceleration my check engine light comes on and flashes for 10-15 seconds and stops. I then give it full throttle again and my truck accelerates like it had full power (first time in a week or so), it seemed the transmission was more aggressive all of a sudden, like it downshifts two gears instead of one at wide open throttle. Kept giving it full throttle and it was working great, except their was an obvious surging at 50% throttle or more. Like the truck was jerking back and forth (imagine flooring it and letting off a little bit and flooring it again constantly).

Later in the drive I floor it and there was a screech, loud clunk, and it felt like my truck hit a wall all at the same time. Kind of felt like a gear slipped in the transmission, my guess would be 4th since I heard it downshift two gears when I was in 6th doing 70mph. Floored it again and it didn't do it. Drove normally all the way to school.

Drove home from school and it reverted back to its loss of power. Also I noticed that the surging was much more apparent, at 50% or more throttle the surging felt like my truck was fighting itself.

Is my truck possessed? It feels like it's possessed.

 

[waskly]

best guess a trans problem.

 

[Divemaster191307]

Sounds a bit like this thread: 06 Explorer 4.6L sputters in over-drive

How many miles on your Ex? Seems like folks have been getting "jerked" starting at 70K on up... I also thought it was my tranny since the sputtering would go away when taking it out of OD. And it was a hit and miss whether flooring it would work. A new set of plugs and no sputtering (I've put 120 miles since the new plugs).

 

[Ford Explorer9]

Sounds a bit like this thread: 06 Explorer 4.6L sputters in over-drive

How many miles on your Ex? Seems like folks have been getting "jerked" starting at 70K on up... I also thought it was my tranny since the sputtering would go away when taking it out of OD. And it was a hit and miss whether flooring it would work. A new set of plugs and no sputtering (I've put 120 miles since the new plugs).

Yeah I took a few people on a ride to see what they thought and the common consensus is a misfire. Did you have a loss of power when this was happening?

 

[Divemaster191307]

Yeah I took a few people on a ride to see what they thought and the common consensus is a misfire. Did you have a loss of power when this was happening?

Oh yeah. When it wouldn't bog down, she still didn't feel like her old self, like when trying to pull into traffic. Granted I don't drive it as much as I used to and there is a "slight" difference between my 911 and the Ex , but I can certainly tell she is much smoother and responsive now. Funny thing is I never got a misfire code or any CEL at all... Which makes me think it was firing but not at full power, just enough not to trigger a CEL, and that also explains the lack of performance.

 

[Ford Explorer9]

Oh yeah. When it wouldn't bog down, she still didn't feel like her old self, like when trying to pull into traffic. Granted I don't drive it as much as I used to and there is a "slight" difference between my 911 and the Ex , but I can certainly tell she is much smoother and responsive now. Funny thing is I never got a misfire code or any CEL at all... Which makes me think it was firing but not at full power, just enough not to trigger a CEL, and that also explains the lack of performance.

What do you mean by bog down? Would it actually decelerate when you were flooring it? Like it was loading up real bad or something?

Yeah besides the CEL that lasted 10-15 seconds I have never had one before this. Or after for that matter. Thank you for the help though

Oh! I almost forgot, it's a 2006 Ford Explorer XLT V8 with 81,000 miles. Which is pretty much in the ball park from what you said about mileage.

I also found that my wiring harness (the one with a big rubber jacket on it) was laying on the metal of my motor. That doesn't quite seem right to me lol.

 

[Town]

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Later in the drive I floor it and there was a screech, loud clunk, and it felt like my truck hit a wall all at the same time......

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This quote from your original post is very similar to my experience with a faulty throttle position sensor. I had noticed what appeared to be a trans vibration or engine misfire occassionally that was getting more frequent, then at 60 mph my car did what you quoted and I limped home with a message center warning. The problem disappeared on a restart. My Ford dealer could not definitively pinpoint the problem but suspected the throttle position sensor. It was replaced and the problem has not occured again in over 2 years.

Your vehicle has an electronic throttle control (throttle by wire) similar to mine. A faulty sensor will cause the PCM to position the throttle plate incorrectly and give rise to all sorts of driveability issues.

Once the sensor is removed, it must be replaced with a new one or poor engine performance will result. Based upon other people's issues with the electronic throttle it appears that the sensor may include a return spring for the throttle plate that can fail or partially fail. There are electrical connectors for the sensor and the throttle motor that may be problematic.

Just an alternative to the plugs and cops and fuel delivery and vacuum leak issues that may fit with the intermittant nature of your problem.

Good luck.

 

[DavidEBSmith]

On the freeway today I accelerate to wide open throttle to pass some guy doing 55 in the fast lane. During acceleration my check engine light comes on and flashes for 10-15 seconds and stops.

Check Engine Light flashing signals a misfire. It flashes as a warning because if the engine is misfiring, it's passing raw gasoline into the catalytic converter which is a bad thing. For some OBD II reason I don't remember, it takes a long misfire or multiple instances of misfire to set the code and turn on the CEL steady.

If it's a misfire you'll also see it more if you press the accelerator lightly than if you tromp on it hard enough to get the tranny to shift down. Also, when you turn off the OD, that raises the RPMs and the misfire is less.

Our Mountaineer started having occasional misfires at around 70K miles, at when we finally took it in at 93K miles it was nearly undriveable. 8 new plugs - 2 were fouled, 2 broke being removed - and it's good as new.

 

[Town]

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For some OBD II reason I don't remember, it takes a long misfire or multiple instances of misfire to set the code and turn on the CEL steady.

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....
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A misfire is defined as a cylinder not contributing to the speed of the engine as expected by the PCM. The Misfire Monitor (a programmed routine in the PCM) continuously checks for engine misfires through engine speed monitoring and it can determine which cylinder(s) are responsible. There are 3 types of misfire, Type 1 and 3 are minor and will not result in the PCM commanding the MIL on unless it occurs under similar conditions for two consecutive trips. Type 2 misfires are the serious ones referred (that may result in engine/cat damage) and the PCM commands the MIL to flash and a steady MIL on after the event has stopped.

 

[Divemaster191307]

What do you mean by bog down? Would it actually decelerate when you were flooring it? Like it was loading up real bad or something?

...

I mean that it felt like it was about to cut out compeletely or like the transmission was about to lock up, to the point where it was actually throwing me forward. When it 1st started doing it, I'd just let off the gas and then floor it, and it would be ok. But before I changed the plugs, it was pretty much a safe bet that flooring it was going to be a problem.

 

[Ford Explorer9]

This quote from your original post is very similar to my experience with a faulty throttle position sensor. I had noticed what appeared to be a trans vibration or engine misfire occassionally that was getting more frequent, then at 60 mph my car did what you quoted and I limped home with a message center warning. The problem disappeared on a restart. My Ford dealer could not definitively pinpoint the problem but suspected the throttle position sensor. It was replaced and the problem has not occured again in over 2 years.

Your vehicle has an electronic throttle control (throttle by wire) similar to mine. A faulty sensor will cause the PCM to position the throttle plate incorrectly and give rise to all sorts of driveability issues.

Once the sensor is removed, it must be replaced with a new one or poor engine performance will result. Based upon other people's issues with the electronic throttle it appears that the sensor may include a return spring for the throttle plate that can fail or partially fail. There are electrical connectors for the sensor and the throttle motor that may be problematic.

Just an alternative to the plugs and cops and fuel delivery and vacuum leak issues that may fit with the intermittant nature of your problem.

Good luck.

That would make sense. Especially since it has been rather unresponsive, such as giving it 30% throttle is about the same as 100% throttle. Would it make more sense that it would be the sensor than a spark plug problem since it runs fine at idle and low acceleration? I'm glad you mentioned it!

 

[Ford Explorer9]

Check Engine Light flashing signals a misfire. It flashes as a warning because if the engine is misfiring, it's passing raw gasoline into the catalytic converter which is a bad thing. For some OBD II reason I don't remember, it takes a long misfire or multiple instances of misfire to set the code and turn on the CEL steady.

If it's a misfire you'll also see it more if you press the accelerator lightly than if you tromp on it hard enough to get the tranny to shift down. Also, when you turn off the OD, that raises the RPMs and the misfire is less.

Our Mountaineer started having occasional misfires at around 70K miles, at when we finally took it in at 93K miles it was nearly undriveable. 8 new plugs - 2 were fouled, 2 broke being removed - and it's good as new.

It actually only shows with 50% or more throttle. Idle and low acceleration doesn't seem to do anything noticeable. It actually runs excellent at low rpms. Could it still be a misfire?

 

[Ford Explorer9]

I mean that it felt like it was about to cut out compeletely or like the transmission was about to lock up, to the point where it was actually throwing me forward. When it 1st started doing it, I'd just let off the gas and then floor it, and it would be ok. But before I changed the plugs, it was pretty much a safe bet that flooring it was going to be a problem.

Later that day after it happened the first time I was going up a steep hill flooring it and it downshifted so hard it actually knocked the breath out of me. Not fun

 

[Town]

That would make sense. Especially since it has been rather unresponsive, such as giving it 30% throttle is about the same as 100% throttle. Would it make more sense that it would be the sensor than a spark plug problem since it runs fine at idle and low acceleration? I'm glad you mentioned it!

This quote relates to the possibility of a throttle plate control sensor problem.

As has been noted previously a misfire that causes a major engine power loss is going to be very noticeable through the MIL flashing and DTC(s) being present.

The symptoms that you are experiencing could relate to the air/fuel system not able to provide sufficient volume at higher throttle openings, but that would likely be more progressive than you are experiencing. Your symptoms sound more like the PCM getting incorrect info and responding accordingly, and sometimes controlling the inputs to the TCM and causing immediate down shifts of several gears due to the electronic throttle control and sensor detecting an issue. The deceleration possible with the PCM instructing all systems to slow the car can be quite dramatic.

Just my opinion

 

[Ford Explorer9]

I got it back from the mechanic today. He didn't notice any surging but he said that it was pinging really bad and that I need to use higher octane fuel.

Also it apparently had two codes saved in the history from when it had the check engine light flashing. I can't remember exactly what the mechanic said but it had to do with the intake and how at 4k rpm something opens up to increase power or something and how they were stuck shut.

So anyways I guess the timing is somehow off, any ideas as to what is causing this?

 

[Town]

I got it back from the mechanic today. He didn't notice any surging but he said that it was pinging really bad and that I need to use higher octane fuel.

Also it apparently had two codes saved in the history from when it had the check engine light flashing. I can't remember exactly what the mechanic said but it had to do with the intake and how at 4k rpm something opens up to increase power or something and how they were stuck shut.

So anyways I guess the timing is somehow off, any ideas as to what is causing this?

Using higher octane fuel than Ford recommends may just be masking a problem, so it is a short term fix while you determine the real cause.

Usually pinging is not caused by ign timing because that is fixed in the PCM and related sensors/modules. There is a knock sensor that will retard the ign if pinging (detonation) is detected at a much earlier point than a person could detect. Usually some part of the engine is overheating and the compressed air/fuel is igniting on this hot surface. The flame spread is uncontrolled and much earlier than the ign timing would dictate. The flame front is very destructive and will erode the pistons and cylinder head doing great damage.

Excess carbon in the combustion chamber is a prime cause; a lean mxture will promote detonation; an overly hot engine due to cooling issues but this will cause the PCM to go into safe mode to limp you home; a worn ground electrode out in the fuel/air flow may also contribute.

Some V6 Ford engines have a runner in the intake valley that opens at high throttle openings to improve power. On the V8 3 valve there is a feature called "Charge Motion Control Valve" that fits at the back and low down on the intake. It has an electrical connector. I have not seen a description of this yet, but it could be a feature to allow a smaller intake cross section at lower engine speed and open up the intake cross section at high engine speed to make more power. Can you get the retrieved codes? Some research required there.

I will see what I can find.

 

[Town]

Here is Ford's description from 2004 of the Charge Motion control Valve: http://media.ford.com/article_display.cfm?article_id=13620 it is a little ways down the page under its own sub-heading. Seems to apply to all the Triton 3 valve engines, including the 4.6.

Now to find out how to fix the problem(s) with it.

 

[Ford Explorer9]

Excess carbon in the combustion chamber is a prime cause; a lean mixture will promote detonation; an overly hot engine due to cooling issues but this will cause the PCM to go into safe mode to limp you home; a worn ground electrode out in the fuel/air flow may also contribute.

What would cause excess carbon in the combustion chamber? Also would the airflow sensors be a possible cause of a lean mixture?

Yeah I'm not quite liking the answers the mechanic is giving me, basically just telling me to drive it until it breaks. Not exactly what I want to do.

Thank you for the help! Much appreciated!

 

[Town]

What would cause excess carbon in the combustion chamber? Also would the airflow sensors be a possible cause of a lean mixture?

Yeah I'm not quite liking the answers the mechanic is giving me, basically just telling me to drive it until it breaks. Not exactly what I want to do.

Thank you for the help! Much appreciated!

Carbon buildup is usually from a rich mixture such as an idling engine, in town driving, etc. Also from burning small amounts of oil. The name brand gas includes cleaning agents but when gas is sold to "no name" outlets it reportedly may have less or none.

I expect that you have a clean air filter and the tube attaching to the throttle body is free from cuts or openings. If all OK then the MAF would be the primary source of air flow measurement into the engine. If there is an air leak after the MAF then the PCM will get wrong air flow info. The MAF relies on the air flow changing the resistance in a wire in the sensor. Any accumulation of material on the sensor wire or a faulty wire will give wrong info to the PCM. The PCM could set a lean mixture but it does have the O2 sensor readings to confirm air/fuel ratios. A bad MAF can cause driveability problems. Ford do not recommend cleaning, only replacement, but many do clean them but no residue must be left behind. The oil coated air filters are not recommended because they do put oil on the MAF according to Ford (but K&N challenge that).

Another cause for fuel/air mixture problems in the 3v engine is the charge motion control valve. It provides tubulence in the air stream at lower throttle openings to give better performance. At higher throttle openings the PCM controls an electric motor to open a butterfly vave to provide more flow. Your mechanic said the device was stuck, so if stuck open then the low speed mixture will be wrong and carbon buildup (like direct injection problem with intake valve carbon buildup) may occur and a lean mixture because of stratified air and fuel charge could cause problems. There is a kit to eliminate the charge motion control valve system but this requires a PCM tune (change to the PCM program) for it to work, so a faulty system makes a significant difference.

I would focus on your mechanic's advice that the charge control system is stuck since this is the most likely cause of your problems. The 3.8 liter V6 and 3 liter duratec 4 valve used to suffer from a similar problem with their intake runner control system.

Good luck.

 

[Ford Explorer9]

Carbon buildup is usually from a rich mixture such as an idling engine, in town driving, etc. Also from burning small amounts of oil. The name brand gas includes cleaning agents but when gas is sold to "no name" outlets it reportedly may have less or none.

I expect that you have a clean air filter and the tube attaching to the throttle body is free from cuts or openings. If all OK then the MAF would be the primary source of air flow measurement into the engine. If there is an air leak after the MAF then the PCM will get wrong air flow info. The MAF relies on the air flow changing the resistance in a wire in the sensor. Any accumulation of material on the sensor wire or a faulty wire will give wrong info to the PCM. The PCM could set a lean mixture but it does have the O2 sensor readings to confirm air/fuel ratios. A bad MAF can cause driveability problems. Ford do not recommend cleaning, only replacement, but many do clean them but no residue must be left behind. The oil coated air filters are not recommended because they do put oil on the MAF according to Ford (but K&N challenge that).

Another cause for fuel/air mixture problems in the 3v engine is the charge motion control valve. It provides tubulence in the air stream at lower throttle openings to give better performance. At higher throttle openings the PCM controls an electric motor to open a butterfly vave to provide more flow. Your mechanic said the device was stuck, so if stuck open then the low speed mixture will be wrong and carbon buildup (like direct injection problem with intake valve carbon buildup) may occur and a lean mixture because of stratified air and fuel charge could cause problems. There is a kit to eliminate the charge motion control valve system but this requires a PCM tune (change to the PCM program) for it to work, so a faulty system makes a significant difference.

I would focus on your mechanic's advice that the charge control system is stuck since this is the most likely cause of your problems. The 3.8 liter V6 and 3 liter duratec 4 valve used to suffer from a similar problem with their intake runner control system.

Good luck.

So the check engine light came on again while accelerating right around 4k rpm. It flashed like before and just disappeared after a few seconds.

I tried accelerating passed 4k rpm again and that's when the surging happened it seems. Although it doesn't always happen only 50% of the time. So I'm guessing the valve is partially working, which I imagine is why the CEL doesn't come on permanently.

So the charge motion control valve sounds like the culprit. I would also like to change adjectives on how to describe acceleration after 4k rpm, it feels like the truck is "twitching". Like I'm hitting tiny bumps in the road randomly that aren't there. What was weird also was around 1900 rpm the trucks rpm was jumping around like crazy for a moment. Going between 1900 and 2k like the needle didn't know what to do. Only did it once though.

Thank you so much again. You have been a hundred times more helpful than my mechanic.

*EDIT* I forgot to mention that I think what he said was the device was stuck shut according to the code. But he said it must be working now since the CEL didn't come on. Hence why I think it is only partially working.