Well, had a chance to make another 'elevation run' up to Paradise with a new vent hose as your post showed and the new spark plug wires suggested by the mechanic. The sharp, notable stutter was/is gone. I did notice a mild throttle fluctuation at around the same point the very noticeable stutter took place. Suspect the vacuum induced "sharp, notable stutter" masked the very slight throttle fluctuation as they seem to involve different components (my guess). Will research further and repost, but progress is being made with my rigs issue(s).

 

*IF* that doesn't fix it, go with Seafoam in a near empty tank.
Once the motor gets the mix in the fuel system (idling 20 mins or driving 5 minutes) let it set overnight.
Morning drive, stay close to home or your favorite & trusted repair center.
Also do use fuel cleaners about every 1/2 doz or so fill-ups.

*IF* #2. Still might have a vacuum leak, even a pinhole can cause your symptom.
I had the exact same stumble issue with my Goldwing. 4mm hose had a pinhole in the outside bend. Was a BEAR!!! to find.

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Had run two different injector cleaners thru the system when the problem first began, but both times, they were diluted by a full tank. Also installed new fuel & air filter. Will spend a bit more time and double check/monitor vacuum with a gauge that will be mounted to bottom of dash. Appreciate the feedback and suggestions. Fortunately, around town driving has not seemed impacted.

 

Have had occasion to do a number of trips into the foothills to do some dry brush removal on our now empty lots. The stutter/stumble issue has not returned but the rpm drift continues. I drop from overdrive at the base of the climb and generally try to maintain 55 mph. At about mid climb throttle/speed/rpm will sometimes drift up and down a bit. My last run a couple of days ago, i looked at the tach caught the needle 'floating' between 2500 and 3200 rpm. The sensation accompanying this drifting was gradual as if my foot were pushing, or lifting off the gas pedal in a slow, controlled manner, though i doubt that was the case. A firmer push got the trans to downshift, and proceeded up and over the hill at around 60 mph and no further float until i began climbing the next hill. My return trip (64 miles) is down the hill then mostly flat with a couple of medium rollers. No issues at all with those conditions. Will see if i can install a vacuum guage that i purchased with my plugs and wires.

 

I KNOW - i know old post but just reiterating. The use of different fuel system cleaners is a great choice since one has a mix for sludge dissipation, others for shellac and even yet more others for carbon. A knowledgeable use of which to use 1st, 2nd and 3rd can be critical. Don't want chunks plugging small orifices and knowing what issue(s) you have helps tremendously.

HOPEFULLY you have this straightened out by now.

 

Thanks Vern, that was the first thing i did at the beginning of this whole situation, but certainly not adversed to another application. Though this situation has been on going for both me and HT08 for sometime, it is still unresolved and very frustrating. For me, the conditions needed to make me aware that something is amiss are unique. The engine needs to be under a moderate load. I now live in very flat country and generally only drive around town. Given minimal engine loads, truck starts, idles and runs fine. When required to drive up into the foothills to work on our property, i notice this erratic running. Now oddly, this was first experienced after i had my water pump gasket replaced as it started leaking. Guess this is a big job as the engine needs to be lifted off its mounts to replace the pan gasket and front seal. Not sure if any vacuum lines were damaged or loosened, but the cable clamp for the transmission (auto) selector had to be readjusted (by me) as the gear selector was left always showing between positions. I did some research on Youtube and managed to get the cable stop positioner almost spot on, finished up with the fine adjustment under the dash. So as of 6/8/2020 This issue is still very real and as always, i am hesitant to spend gobs of money having a shop try and think things through. Any suggestions are still much appreciated. Again, the truck is a 2002, but is still under a 100,000 miles. Thanks, and take care all.

 

I have the Ranger 1998 3.0
I read your hesitation issue.
MAYBE a throttle plate shaft is worn. Some have teflon and they wear fast. I've fixed one with an O-ring, super lucky on the size.
Permatex 2 (P2) works wonders for plugging pinholes on hard surfaces, like throttle plates.
P2 also does GREAT on coolant hose seal tho just a bit difficult removing later. EZ cleaned with carb-cleaner. Started that in the 70s and NEVER had a leak.
Thick grease around the intake plate & connections helps find large area leaks, easily cleaned later.

__ Few more possible ideas. __
I assume you've pressure & flow tested your fuel pump.
One of my old vehicles I gently added air pressure to a vacuum hose. Then with several smokey pieces of cardboard went around the motor looking for a leak. Has to be done in a garage with door closed, even dead wind days theirs heat/cool surfaces that create wind BUT might get lucky. USE A GOOD LIGHT A MUST to see pinhole waffs.
Trans huh, is there a vac line going down to it? Old cars did, unknown about new.
Again pinholes are a bear, but if you do have one any silicone pushed into it will seal it. $-saver. Wrap it with electrical tape as a future reminder.
Back to hesitation. Our GoldWings have a similar issue. In the carb are large diaphragms. Where they fold over micro cracks develop, just off idle hesitation. You may not have these but could spark an idea.
. . . HOPE you find it soon.
.
My truck has 183K and timing acts like it jumped timing gear teeth. Haven't opened it up yet, something "FEELS" like it's not the chain. No codes.
Frustration over these newer vehicles & electronic (ah-hem) STUFF holds me back from working on it, but will. I'm scouting for other venues like short blocks due to mileage. I have the knowledge to rebuild just no garage.
Since the Hall Effect in Chrysler's 1st came out in the 70s I've always said Mfg's NEED TO stock the electronic parts much longer than 7 years. With dash gauges being absolutely paramount or at least newer ones be backwards compatible. It's NUTS scrapping a fine running vehicle just because of ONE required $100 or less electronic part can't be replaced.
OK, rant over.

 

UPDATE. It has been a few months since I reported my truck in the shop from a careless truck driver making a delivery and hitting my truck. I have it back and been driving it again.

I had to fix a power steering leak near the pump and for easier access I removed the inner fender liner. I also discovered that I had direct access to the Oxygen sensor(s). At 245k miles my Oxygen sensors were original so ordered and replaced both pre-cat ones on both banks. I have another thread here where I list the part numbers, if one needs it just do a search and you will see it.

Since the Oxygen sensor replacement I no longer get the hesitation that I use to get during mid or full throttle, it has gone away and I put it to the test every so often and the truck just pulls without hesitation. I just changed the oils at 245,689 miles and today I was getting on the freeway and I pushed it and no stumble just a steady acceleration.

Now I know, or think that I know that the Oxygen Sensors could not have been the culprit here but that is the only thing that has changed except for fixing my power steering leak. So knock on wood my stumbling and hesitation is gone. I hope this helps someone else out that may be experiencing the same or similar issue. Mrgizmow I hope you get a chance to read this!

 

They should be replaced at around the 70k mark, even if there is no check engine light.
There's a type of ceramic and platinum coating inside that gets used up after a while and they start relaying false info back to the PCM, but not enough to produce a CEL.

 

Yes they were definitely Way Overdue! I think BMW recommends 100K miles, so 244 or 245K is stretching it. Hope others read this and think about replacing theirs if they have not. Thanks Jeff

 

Well, per HT08, i just installed Motorcraft Oxygen sensors. Unlike HT08 i have hung a large vacuum gauge on my dash to be on the lookout for troublesome leaks. For what it is worth, my 3.0 2002 Ranger automatic with 94,000 miles was presenting me a vac reading between 16/17. After oxygen sensor install, vac reading seemed to climb to between 18/19. Like HT08, i am not experienced enough to suggest marginal oxygen sensors cause notable cutting out & hesitation. Think that for me, a vacuum leak was the root cause. What seems to have helped dial it all in (for me) were new plugs, plug wires and oxygen sensors. As i have not been 'up the hill' of late, the final test is yet to done, but like HT08, oxygen sensors seemed to provide a smoothness that was noticeable. Take care.

 

Glad to hear there is some improvements. I would like to add that with the new Oxygen sensors my mileage has also improved which is not a bad thing. Thanks for the update mrgizmow and Keep us posted!

 

As local temperatures have dropped a bit below the 100 degree mark it seemed prudent to drive into the foot-hills and do additional clean up on our burnt out lots. This drive always seems to be the real test of engine function/performance. The day before yesterday was able to make it up the hill for the first time in a year without any hiccups, engine ran smooth and strong. I thought, finally, thank God. Yesterday i headed up again for there is still a bit more to do as the town wants all combustibles removed. The drive was again without incident until i came upon a large fully load dump truck on the hill going about 30 mph. When slowed down i soon experienced a odd stuttering sensation. My first thought was that i had drifted a bit to far towards the shoulder of the road and was running over the 'alert' grooves cut into the pavement to alert inattentive drivers that they are heading off the road. The sensation was very physical. The truck has an automatic trans but it felt like a standard trans that needed to be down shifted into a lower gear. Moved the shifter from (D) to (2) and can't say their was any improvement. Just proceed slowly with almost no throttle in (2) and things smoothed out. As we neared the top the grade began to flatten and the dump truck started to slowly gain speed. I shifted into drive and gained speed as well with no further issues. Still have my 3" vac gauge hung from the dash. Reading is generally steady but during the time behind the truck did seem to fluctuate a lot and it seemed the transmission/clutch was confused about what gear to select. As it goes, the vac gauge is very sensitive and even in cruise control you can see when the engine makes the slight throttle adjustment even on flat ground. At idle once warmed up at around 800 rpm it can read from 17 to 19 hg. If watched at idle for a minute or two the needle can slowly drift a bit and back, but not a full point. Now the engine recently had a gasket replaced between timing cover and block as it had a minor water leak as it seems 3.0 engines are prone to. At this point figured it made sense to replace water pump and timing gears/chain. To do this job i understand oil pan gasket should be replaced and for that engine needs to be lifted a bit to gain needed clearance. All this was performed by an independent shop. I had not noticed any engine/running issues before that, but then most of my driving is slow around town stuff.
Any new ideas will be much appreciated. Thanks and take care. Gerry