56mph to 64 mph miss/skip/studder?

my87bomb · Apr 14, 2012

I have searched however, while driving(outside temp doesn't matter engine temp doesn't matter) between the speeds of 56 to 64mph my ranger will start to skip/miss when I try to accelerate the skipping gets worse and turns into a bucking feeling almost as if it is loosing fuel. Driving at 54mph and below and 66mph and above I do not have this problem. I am thinking MAF or TPS? BTW this is on my 99 3.0 flexfuel ext cab auto. 2wd ranger130,000 miles...I recently replaced the plugs and wires(motorcraft) and coil pack(autozone). It was running like dirt when cold prior to this and I searched and found a hose missing from egr area to the pulse sensor. now it runs like a champ except between the speeds as stated above...I have not replaced the fuel filter yet...but...something like that should be constant this is at any rpm just between those certain speeds. only codes (DTC) are lean banks 1 and 2.
Thanks in advance for any and all help.

kodex · May 3, 2012

Could be your EGR system causing your computer to do screwy things with the fuel/air ratio. Try popping it off the throttle body and soaking it in some carb cleaner, but don't you dare get it on the electronic part! Another option would be using MAF sensor cleaner, which is safe on electronics (just gotta make sure it's dry before putting the valve back on.)

-Steve

Rearanger · May 4, 2012

my87bomb said:
I am thinking MAF or TPS?

No guarantee that TPS position is always the same at any speed. Throttle opening depends on engine load. MAF measures air flow/density/temperature so speed I'm thinking is not going to be that defined there as well. I agree that fuel filter does not fit the symptom, although it would be a cheap test. Bucking could be electrical or fuel starvation.

A quick OHM test might see if you have a flat spot in the TPS windings but Ford calls for volt testing the TPS.

How does it behave in all gears independent of speed?

my87bomb · May 7, 2012

Steve - I will have to try that, worst case I need to get an egr valve gasket....

Rear - I did replace the fuel filter, to no avail symptom is still there.
I however, have noticed under very hard acceleration(flooring it) it will produce the same symptoms, i very quickly let off though because of how violent the truck bucks jerks and shakes. When i get back on the throttle...no more than about 30% it accellerates smoothly...untill i hit about 58 or so...

Rearanger · May 8, 2012

Can you check fuel pressure?

my87bomb · Jun 14, 2012

Rear
Not without taking to a garage somewhere...which I think I am about to do! The speed range is getting bigger. It does it now from 54 to about 66.

I took the egr off it looked fine to me, no exsessive build up of carbon or anything. I am about to try the two different sensors by the throttle body.

my87bomb · Jun 29, 2012

UPDATE
I swapped the TPS and MAP sensor one at a time with used ones, no change in symptoms... I know...how do I know the used ones were good(i dont)
I cleaned the MAF w/ Electronics Cleaner(brake cleaner)
and today I performed a compression test...
when looking from the front
3-6
2-5
1-4
starting with #1 122, #2 128, #3 135, #4 137, #5 110, and #6 145...
yes I am concerned about a 35 psi difference between cyl # 5 and 6 but the engine does have around 130,000 miles
Refresh---its a 99 3.0ffv A/T

Rearanger · Jun 29, 2012

I thought the FFV had higher compression to compensate for less energy in alcohol. Those compression #'s look really bad (if gauge is accurate) but I can't see how compression is related to missing at certain RPM range. Was the engine hot when you did the test?

At about 11K miles my compression was between 192 and 185 (I can't find compression spec in my FSM). I don't consider your 130K a lot of miles. My 95 Camry has 185K and 170psi compression, just 8 PSI off new factory spec.

Have you tried getting to the RPM range in all gears and seeing if the problem is the same in all gears at same RPM range or just in top gear at those RPMs?

my87bomb · Jul 1, 2012

Rear
I've read where the valves are different in order to handle the ethanol but haven't heard wether or not the compression went up. As for trying it in different gears, thats the weird part. It has the same skip/buck but at higher rpms in lower gears. I thought it was slaming in and out of O/D. A friend of mind said it may be lock up acting up. So i ut it in low 1 to see if I could get the jerk/miss. It wasn't as violent but it was at higher rpm's
I am thinking of either installing a tach to verify the rpms or just send it to a garage. I personally think it's in my injectors. But I am at a loss when it comes to checking that. because the symptoms only appear while driving. I tried to power brake it with no signs of the skipping/bucking. ?????

masterbrenden · Jul 6, 2012

check the comprestion to what it should be. the flex fuel's do have valve problems and will suck the valve into the head over time and cause a miss at high speed or high load

Earl43P · Jul 6, 2012

Disconnect the vacuum line to the EGR valve and drive it.

If it quits bucking, replace the DPFE.

Lean in Banks 1&2 is very likely to be the infamous PCV 90 degree elbow leaking, which is very common.

my87bomb · Jul 13, 2012

Earl, tried it, and it made no difference...

Rearanger · Jul 14, 2012

my87bomb said:
it made no difference...

Even though I don't have a solution I thought the EGR suggestion was looking for a vac leak at the EGR? Usually vac leaks show up at low RPMs and idle, not higher revs. Since it appears at higher RPMs (all gears) I'm still in there for fuel problem, but if you can't check the pressure on your own then you'll need to take it to a shop. You mentioned injectors, but with no means to test then we could be guessing forever. Diagnosis involves testing and with only a DTC lean code you'll need to dig deeper. Leak down test might give better clue to valve problems than compression, which is terrible on yours if that was a hot engine test. Testing would be easier if truck was on a dyno, so if a shop has one in your area I'd look at taking it there where they could duplicate symptoms with analyzer hooked up.

my87bomb · Jul 14, 2012

Rear while checking the egr I did notice the PVC out of place(popped out)(my guess when I ran the new wires I pulled it out and didn't notice it out of place). I put it back in place and replaced on of the hoses going from the egr line to the DPFE.
I feel fuel as well...I have replaced the fuel filter with no luck. As for testing the fuel system I can check the ohms with a meter while sitting still at an idle But that is not duplicating the problem. My thoughts are having hooked up to the obd2 scanner while driving in order to obtain real time data while duplicating the symptoms would be the most accurate way to diagnose the real problem
When I did the compression test the motor was cold... I do not like working on a hot engine(who does?). I will need to research how to do a leak down test...

my87bomb · Dec 15, 2013

UPDATE
After 6 months of playing in the desert I had lost all patience with this.
Did I mention that I had replaced the cam sensor?!?(Ooops!?!) my bad

I installed the cam position sensor 180 degrees out! Who would of thunk.....

56mph to 64 mph miss/skip/studder?

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