Problem with 1999 Ford Explorer (Eddie Bauer) 4.0L SOHC

At approximately 30-45 mph (1800-2000 RPM) I can feel the engine "lighly bucking" and I have replaced the plugs and plug wires so far thinking that may take care of it, but no such luck, still does the same thing. At higher speeds the engine seems to run great with no bucking at all. Does this sound like a possible injector problem? This has been so annoying that my wife hates to even drive the car in town! I would appreciate any help/suggestions that anyone can offer. I have a Lab Scope if someone would lead me in the right direction on diagnosing this particular issue.

Thanks

Hey obtech!

Do you own a scanner, or have access to one? There's some scope tests we could do, but it might be faster to look at some data during the surge, first. I'd be particularly interested in the fuel trims, long and short, on both banks while surging. It may also be good to look at Mode $06 TID $53 for possible misfire counts.

The fact that it bucks during a cruise makes me wonder about a potential EGR problem. The fastest way to rule this out would be to disconnect and plug the vacuum hose going to the valve itself. Recheck for the symptom - if it's gone, then we can dig deeper into that.

I've also heard of CMP sensor issues causing this, but usually the bucking is much more severe. Anyway, you can also try disconnecting the CMP sensor and driving it. The CMP isn't required for running, it'll just set a code when disconnected.

could be the torque converter. try driving it out of overdrive

I disconnected the CMP and it did not make any difference...but I was surprised that a DTC was not set and no "Check Engine Light"either.

I connected my scanner to the vehicle and I ran the Mode $06 and discovered the following:

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Test ID: $53 ---- Component ID: $04 = 108 misfires (max 13,056)

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$06 = 217 misfires (max 13,056)

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Test ID: $21 ---- Component ID: $00 = 64,816 "FAILED" (max 61,440)

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Test ID: $41 ---- Component ID: $12 = 65,227 "FAILED" (max 896)

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Test ID: $56 ---- Component ID: $00 =65,535 "FAILED" (max 3000)

This has got to be telling me something and hopefully will lead to a successful fix. Any input on the data I pulled from Mode $06 will greatly appreciated.

Thanks for the assistance.

Here is some info from Ford that is free at www.motorcraftservice.com/FreeResources/OBD



Looks like $56 has to do with misfire events, not sure. Maybe someone could comment on this.


This one has to do with the EGR DPFE sensor.


This last one is for the EVAP system, obviously not a concern for what you are having problems with

The test id $53 id $04 is a cylinder specific misfire with 108 events. Cylinder number 5 if I am correct (I always get confused on the numbering).

obtech wrote: I disconnected the CMP and it did not make any difference...but I was surprised that a DTC was not set and no "Check Engine Light"either.

See what I mean? :lol: The CMP sensor doesn't carry much weight on these engines.

I connected my scanner to the vehicle and I ran the Mode $06 and discovered the following:

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Test ID: $53 ---- Component ID: $04 = 108 misfires (max 13,056)

---

$06 = 217 misfires (max 13,056)

---

Test ID: $21 ---- Component ID: $00 = 64,816 "FAILED" (max 61,440)

---

Test ID: $41 ---- Component ID: $12 = 65,227 "FAILED" (max 896)

---

Test ID: $56 ---- Component ID: $00 =65,535 "FAILED" (max 3000)

Thanks to Ro-longo for the Mode $06 data. I believe the cylinder numbers correspond directly to the Component ID? So you'd be looking at cylinder #4 and cylinder #6. Google says the firing order is 1-4-2-5-3-6, so those are NOT companion cylinders, and not shared on the coil pack.

Did you get a chance to look at the fuel trims, or try disconnecting the EGR vacuum hose?

Thanks Rob

I just typed a huge list of crap wrong with that German pos motor and hit submit and I was timed out and had to sign in again,lost it all. Damn it. I do the one finger hunt' n peck, took me for ever. I know you wouldn't think vacuume leak but when it's dead cold spray passengers side rear by fire wall upper and lower intake. It's all plastic and caused some weird problems

Aww, that sucks! I'm a two finger typer and lose my posts that way a lot! I've made a habit of copying the whole thing before I hit Submit.

Those motors are dicey...
Seriously, they converted a 427 pushrod motor to SOHC without putting a timing chain in the back! Maybe if they made a head specific for each side of the engine the 4.0 could have continued being a dependable work horse... But I digress.

Glad you got to the bottom of it!

Just watch out for the craptastic torx screws holding the intake together. They look more at home on a deck than an engine. (Making it hard for me to stick up for you guys Ford...). And disturbing the plastic thermostat housing may prove to be a can of worms.

Ok, copy how? Seriously not being a smartas. Using an iPad Pro at the moment a lot of times my iPhone 6s Italian. I've touched on the screen and let go and the little black boxes pop up,but nothing says copy.

Rockyroad wrote: Ok, copy how? Seriously not being a smartas. Using an iPad Pro at the moment a lot of times my iPhone 6s Italian. I've touched on the screen and let go and the little black boxes pop up,but nothing says copy.

I'll have to ask my coworker who owns an iPhone, 'cause I have no idea how it works on Mac products. :blush: