Intermittent engine "stutter" - Ford Explorer

[grey26]

The vehicle:# 2000 Ford Truck Explorer 4WD 4.0L EFI SOHC 6cyl, approx. 152k miles

The problem: Occasionally while driving, my truck will do something I don't know how to describe other than to "stutter." The problem is that it feels like I lose all power for 1-2 seconds, which then causes the vehicle to start to slow down, then the power is restored which results in a jerk or lunge forward. The RPM's drop off during the loss of power and then jump back up to where they were when the power is restored. During the loss of power, the gas pedal feels useless. This has happened 5 times now in the past 24 months - very intermittent. Two of the times it happened after accelerating through an intersection after having been stopped. The other three times it happened while cruising at a steady speed (twice around 40mph and once around 70mph). Half of the time the problem went away after just a few seconds, the other half the problem persisted until I stopped the engine. Fortunately, every time it’s happened I’ve been close to my destination so I've been able to limp along a few minutes to get where I'm going. After letting the truck sit a couple of hours, the problem goes away and doesn’t return for several months.
I've checked with three different transmission shops and they've each said that since the RPM's are dropping and not spiking during the deceleration it's most likely not a transmission problem. Because it's so intermittent, my local repair shop and a local Ford dealership both say they can't find anything wrong with it since we don't know how to recreate the problem on demand and have no suggestions. The first time the incident happened, it was roughly 2 weeks after I had replaced the fuel filter with a Napa brand filter. When the incident happened I immediately replaced the fuel filter with a Motorcraft brand filter thinking that the Napa filter may have been the problem. Also, at the advice of some mechanics shortly after the first incident, I switched to mid-grade gas (up from regular) and made cleaning the throttle body and MAFS part of my regular maintenance when I change the oil, oil filter, and air filter. I’ve also noticed a loss of about 3-4 mpg during this time frame. I have ran 3 bottles of RXP through the gas tank as well over the last 24 months.

Here’s a list of the things I’ve done in the last 24 months, in addition to changing oil and air filter every 5k miles:

PCV replaced – 1/15/14
Spark plugs and wires replaced 1/25/14
Fuel filter – 2/15/14 (first time, second time about 2 weeks later)
Problem first occurred towards end of February, 2014
Transmission fluid – drained and filled (not flushed) 8/30/14
DPFE Sensor - May 2016
Problem last occurred February 2017, a couple of days before EGR was replaced.
EGR Valve - February 2017
Replaced ignition coil pack March 2017

Clean MAFS – (every 5k miles since problem began)
Clean throttle body – (every 5k miles since problem began)

Has anyone experienced this before? Any advice as to what my next step(s) should be?

Update:
CEL light finally came on in Feb 2017 after driving the car for 30 minutes while problem was present. Codes P0171 and P0174 ("System Too Lean Bank 1" "... Bank 2"). See post on March 22, 2017 for more details.

The truck idles fine, even when it's acting up. When the problem is occurring, it only stumbles/stutters when pushing on the gas pedal. The only time I've had a rough start was once or twice when the outside temps were below 30 degrees.

 

[evasive]

I know this is an older thread but did you ever solve this? I'm having the exact same issue with my 2000 Sport.


Thanks.

 

[Flash]

There are 2 things that will turn your engine off like that; lack of spark and lack of fuel.

As you said it's hard to test if it's intermittent.

Check the fuel pump relay and fuse.
Check the coil.

If it were the crank sensor it should throw a code.

Your fuel pump is probably coming to the end of it's life at 152k, I think they go at around 160 - 170; worse in cold areas.

 

[FPGT24]

I had this EXACT same issue on my 98. I was told it was the DPFE sensor. Go to my profile and click on the link for all my posts. i had a pretty good thread going about it.

 

[FPGT24]

There are 2 things that will turn your engine off like that; lack of spark and lack of fuel.

As you said it's hard to test if it's intermittent.

Check the fuel pump relay and fuse.
Check the coil.

If it were the crank sensor it should throw a code.

Your fuel pump is probably coming to the end of it's life at 152k, I think they go at around 160 - 170; worse in cold areas.

No. None of the things you said. It's a failing DPFE sensor.

 

[Dave98XLT]

I noticed you said you had recently changed your spark plugs. The spark plug interval on the SOHC is 100k miles. When I did my 1st plug change, shortly afterward I had to change the sparkplug wires, too, as it ran terrible. Shortly after that, a check engine light for the front 2 oxygen sensors came on. After changing the 2 front ox sensors and ignition wires all was well for another 100k miles. I must add, I did all of the other maintenance, filters, oil, cleaning TB/MAF, PCV.

I have never heard of this DPFE sensor but it could also be the cause.

But if you want a really clean running SOHC, I recommend changing the plugs, wires and front O2 sensors at the same time, every 100k. Also recommend cleaning the MAF/TB and replacing the PCV regularly, too.

 

[grey26]

Evasive, I haven't done anything to fix the problem yet. I checked the basics and didn't find anything obvious like a vacuum leak, damaged hoses/wiring, etc. The problem is very intermittent, happening once every several months, so it's going to be hard to find the problem with any component testing.

I found a new Motorcraft DPFE sensor on Amazon for $60 (local dealership wants $115!). That'll arrive tomorrow and will get installed that evening. Only time will tell I guess if that fixed the problem but from what I've read on various websites/forums about the sensor (thanks for pointing me in that direction, FPGT24), that sounds like my best bet and the symptoms of a failing sensor match what I'm experiencing.

Flash and Dave98XLT, thanks for your comments as well. If the DPFE sensor doesn't fix the problem, I'll definitely checkout the items you suggested next.

Thanks again to everyone who's commented.

 

[Flash]

I found a new Motorcraft DPFE sensor on Amazon for $60 (local dealership wants $115!). .

Reuse the short rubber hoses on the DPFE you have or preferably the new ones that hopefully come with the new part.
It's special heat resistant hose that doesn't burn up like the ordinary rubber hose some previous owner of my Explorer used.

 

[grey26]

Good to know, Flash, and thanks for taking the time to pass that on to me. I don't think the sensor comes with new hoses so you may have just saved me from more headaches!

 

[bobflood]

New DPFE will not come with new hoses. These are special high temperature hoses; new sets are commonly available in most auto part stores. The hoses are two different diameters. Good luck.

 

[grey26]

New DPFE will not come with new hoses.

You are correct. The DPFE arrived today and did not come with new hoses. The old hoses appear to be fine and I installed the new DPFE this afternoon in a few minutes. Now, I guess I wait 6 months to see if the problem happens again...

 

[grey26]

I thought I was in the clear. After 8 months of running well, the problem came back at the end of February. As always, I was just down the street from my destination so I kept driving around the neighborhood for about 30 minutes to see if a part would finally die or a CEL would come on. At first, it was just the occasional stumble/stutter when accelerating but the longer I drove it the more and more consistent it became until the last 10 minutes when all it would do is limp along. This time it finally threw a CEL. Went to my local mechanic the next day and the codes are P0171 and P0174 ("System Too Lean Bank 1" and "System Too Lean Bank 2"). The shop couldn't find any vacuum leaks or recreate the problem and opted for a smoke test. They said the EGR valve was stuck (I believe they said it was stuck open). They stated they couldn't say with confidence that the EGR valve was the only root cause of my stutter/stumble problem but that the EGR valve was bad. $350 and a couple hours later I was on my way. Fast forward 3 weeks after the EGR was replaced and I was driving my car a couple of days ago when the problem returned. As always, I was just a couple of minutes from home so I kept driving it. The problem occurred intermittently in brief 2-3 second spurts several times before I shut the engine off and parked the car. No CEL lights but I'm assuming it's because I didn't drive the car long enough to cause one like I did last month. Just as in previous instances, after the car was parked for a couple of hours, it ran fine the next time I drove it.

Any ideas? O2 sensors? Coil packs?

 

[SWIGIN]

With the lean codes I'd say fuel pump.

 

[grey26]

SWIGIN, thanks for your reply. How would I go about confirming it's the fuel pump before replacing it? I've already thrown over $600 at this problem and am hoping to be certain the next thing I fix/change is the culprit.

 

[SWIGIN]

IMHO, If you have over 100,000 miles on the pump I'd rather change it at my leisure then have it leave me sit or cause problems.

Most pumps last much longer then that but if that vehicle was owned by the type that always drives on fumes, that is very hard on a fuel pump. To me it is $100 peace of mind.

But to answer your question, I have no idea how to test since I have never needed to using the technique above. But the lean codes tell me it's a fuel problem.

 

[Spuddy]

P0171 & P0174 codes are often and notoriously associated with leaking intake manifold gaskets. Those could be defined as vacuum leaks and your shop probably should have detected that, but...

I don't see these on your list of replaced items. They are highly suspect at 150K, if not.

Do you also have issues starting the motor and a rough idle in the cold?

I also don't see on your list that you either replaced or cleaned your IAC valve. It also has a gasket. That could probably also use a cleaning at 150K.

I might try both of these cheap repairs first before a fuel pump.

 

[Spuddy]

Could be a lot of things. Cheer up. It's probably not the O2 sensors or cats. Service manual sez:

----------
Diagnostic Trouble Codes (DTCs) P0171 bank 1 (Cylinder 1) and DTC P0174 bank 2 indicate the fuel/air ratio is too lean. The fuel trim system is at the rich correction limit.

Possible causes:

Fuel system

• Excessive fuel pressure.
• Leaking fuel injector(s).
• Leaking fuel pressure regulator.
• Low fuel pressure or running out of fuel.
• Contaminated fuel injector(s).
• Vapor management valve (VMV) leaking.

Induction system

• Air leaks after the MAF.
• Vacuum leaks (vacuum lines and gaskets).
• Restricted air inlet.
• PCV system.
• Fuel purge system.
• Improperly seated engine oil dipstick.

EGR System

• leaking gasket.
• Stuck open EGR valve.
• Leaking diaphragm.

Base engine

• Oil overfill.
• Cam timing.
• Cylinder compression.
• Exhaust leaks before or near the HO2S(s).
• Check intake air system for leaks, obstructions and damage.
• Check air cleaner element, air cleaner housing for blockage.
• Verify integrity of the PCV system.
• Check for vacuum leaks.

----------

I'd start here:
http://www.explorerforum.com/forums/index.php?threads/lean-condition-procedure.265785/#post-2364255

This guy knows his stuff. Good luck.

Long list, isn't it? But, it looks like you've already got a good head start.

 

[96eb96]

We can all guess at this. Lets get some real numbers.

I would like to know fuel trims (LT AND ST) at:
1) Idle
2) 1500 RPM
3) 2500 RPM

Also freeze frame OBD data from those two codes.

Also, I would like to know the BARO PID. You can get this from software such as forscan.
You may have a clean MAF but it could still be reading off spec.

 

[grey26]

Thanks for everyone's comments/suggestions. This is a very frustrating problem and I'm hopeful it'll be an easy fix once the problem is isolated. It's certainly nerve wracking to lose all acceleration when trying to take a left turn in front of quickly approaching oncoming traffic! I have a long list of stuff it could be (thanks Spuddy) and will start with the ones that are easy/cheap. Fortunately, my commute to work is 1 mile and my wife travels several days a week so I can take my time with this and borrow her car. Plus, I always have a bicycle I guess...

96eb96, how can i go about obtaining these #'s? If the truck runs fine 99% of the time and normally only acts up once or twice a year, would I have to obtain these #'s while it's acting up that 1% of the time or would it still be helpful to get this info when it seems to be running normal? I'm guessing that question would apply to other things like checking fuel pressure, etc? If I check the fuel pressure when the truck is running fine, I'm guessing I wouldn't obtain any info that will help narrow this problem down?

I'll edit my original post but the truck idles OK and the only time I've noticed a rough start was once or twice when the outside temps were under 30 degrees. Even when the problem is occurring, the truck idles fine. It's only when I push on the gas pedal that it stutters/stumbles (in park or drive).

 

[grey26]

06eb96, I purchased a BAFX Products 34t5 Bluetooth OBDii Scan Tool device. It doesn't look like it does freeze frame and I'm not sure that it's compatible with Forscan but it does give LTFT and STFT for both Bank 1 and Bank 2. I've been playing around with the upload settings and think I have it all figured out. I haven't been able to drive it more than a couple of miles at a time this week so I'm planning on getting it out this weekend for a long drive to heat the engine up to normal operating temperature and then grabbing the #'s that you requested. Other than LTFT/STFT for Bank 1 and Bank 2, do you want any other info? Coolant temp, etc? How long should I keep the engine at idle, 1500rpm, and 2500rpm while the device is logging?