RPM's jump back and forth while driving steady

[clawhn1]

93 xlt...i pretty much noticed this overnight..

i was driving on the freeway and i keep the pedal steady at around 1800 rpm, then all of a sudden without pushing the pedal it jumps quickly to 2500 rpm ,then about 2-5 seconds later goes back down to 1800 then a few seconds later will jump again....i also wan to add, that this is while the air conditioner compressor is off...maybe the compressor is engaging on its own? but i dont think so, because you can always hear the compressor click on and off and i dont hear this happening.

it keeps doing this

now, i need to know whats wrong because i dont trust any of the mechanics around here in my area and i got little money

at first i thought maybe its just getting a surge of clean air from the intake and getting a power boost, but theres something wrong because it happens back and forth every few seconds sometimes it will take about 1 minute, but still , its like someone is gunning the accelerator while im driving steady ....

i recently 2 weeks ago did a mod, i installed a oil breather to the engine and put on a cap on the air intake tube where the oil hose was attached...ive seen this done on here at this forum and i figured it would give me more colder fresher air and it worked, the truck was immediately faster and smoother..

problem is now i have this problem and i dont know much about cars

my guess would be either fuel pump or electric relay?oxygen sensor? air fuel mixture problem sensor from maf?

i recently cleaned the maf sensor with carborator cleaner same with throttle

there are no noises,no clicks, the tranny seems to shift good ,automatic i have,

i recently cleaned the throttle body because it was literally covered in grime

thats why i replaced the oil hose...i think my car is burning oil (220000 miles) and so id rather have clean air for fuel burning, the manifold and trottle was very dirty

anyways,can anyone have this problem tell me what it is

btw, off topic,but my trottle was so dirty that when opened all the way it would stick because of the grime, a couple times on the freeway it would stick and id have to literally reach down while going 80 mph and grab the accelerater and pull it forward....nearly killed me and my wife

i have a ton of mods to my truck...i have a bbk enlarged trotle body, 5.0 maf,

 

[deamon3]

Mine does the that even when the air con is off , just having the blower on with make mine do the same.

 

[mrboyle]

Does the truck accelerate or "pull" like you just gave it gas, or does the RPM fluctuate and there is no change in vehicle speed?
Next time it happens try putting the tranny in D not OD and run it for a while. If the fluctuation goes away, the problem is the transmission is "hunting" between drive and overdrive. What causes this is that the vehicle is traveling at a speed that is almost too slow for overdrive yet there is enough throttle input/ load on the vehicle that it starts to bog the engine down. To compensate the tranny downshifts. The load suddenly goes away and the tranny upshifts into overdrive. It will continue to do this until you either speed up or slow down. The most likely cause is that the od in the tranny is statring to wear and not able to hold as well as it use to.

 

[bgh1441]

That would be my guess and the first thing i thought of is the overdrive engaging and disengaging. Makes the most sense

 

[F150hybred]

Your RPM readings support the overdrive cycling on and off. If your bucking a head wind or have small number gears with big tires... or both, that would be enough to do it. I had the same problem with mine but was solved with a gear swap.

 

[clawhn1]

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[clawhn1]

EDIT: i fixed the problem for free and in about 3 minutes.....i reattached the oil intake hose and removed the oil breather and it rides steady now....actaully seems faster to, even my wife thinks it has more pep on the freeway

but that adds another question, i see people using the oil breather mod and using the cold air intake, but when i did the breather and capped off the hole on the plastic intake stock tube, it started this RPM problem....i wonder why only in my car ?

i forgot to add, that about 3 months ago i added for the first time large 31/10/15 tires to the rear

so is it my overdrive tranny or the differential gears in the rear axle?

help me so i can tell the mechanic a heads up

also, to answer the guys question, the truck does get a power boost from this gain, its not just the dial moving up the car also gets a jolt of energy

 

[Flip4ford]

SOunds like it is down shifting and your tranny is on the way out.

 

[clawhn1]

ok i disagree, my tranny was completely rebuilt just 2 years ago cost me like 2300

it lasted like 160000 on the original and they told me they have never seen any tranny last that long on stock.....since i took care of it

it started slipping, so i got it replaced, and it runs great

but like i said, just before i read your post i was about to post this ina new thread...i just read this thread http://www.explorerforum.com/forums/showthread.php?t=159179&page=8

and there are different view points on oil breather...

after i changed my breather back to stock, i was hitting 90 on freeway very easily and it still shifts and runs brand new (with the help of mods of course)

actually, the truck is fast enough, it seems like the more i try to mod it the slower it gets...

ill start a new thread because i want to solve this oil breather question,is it good or bad?

 

[clawhn1]

SOunds like it is down shifting and your tranny is on the way out.

but down shifting would make the car slow down right? like slip from 3 to 2 gear?

thats not what was happening, i would hit gear 3, then all of a sudden id get a power surge and the car would rise about another 1000 rpm on its own with a power increase then down shift back to my original speed

basically it would upward shift(is that the term?) then go back to normal

for instance...driving 60mph at a steady 1800rpm,then suddenly jumps to 2500 rpm and hits about 64mph,then slows back suddenly to 1800 and 60mph...and while its doing this you feel a "back and forth" type of feeling while your driving ...like im pushing and releasing

 

[loner4u69]

Tranny's Slippin

 

[monicacrimmins]

Help a girl!!

Ok, so my 1994 Explorer is doing everything spoken about in this forum. The RPMS jump, speed does jump also, it pulls also, there seems to be no pattern to how or when it happens. I do have it in OD most of the time. I end up putting it in N at stop lights/signs because it lunges and I am afraid of rear ending someone. Help a girl out. What can I do to get this to stop? I love this vehicle and wouldn't trade it for the world. What is a simple solution that I can start with and then build from there? I have had suggestions of flushing the tranny, throttle position sensor (I replaced), replacing the tranny and so on.

Thanks guys!!

 

[Flip4ford]

Hot oil on the air intake temp sensor will do this as well. Changing the pcv vaulve can cure that.