alright, so this is probably a common problem, ive seen a lot of people asking about similar problems. i have an RPM fluctuation happening on the freeway and even at the 45-50 mph range while holding steady throttle. once i get up to speed, and i let off of the gas and hold it steady to maintain constant speed with or without cruise control, with or without a/c on, it fluctuates from (for example) 2000 to like 2300 rpm and back down, it will do it maybe 5-10 times and sometimes it will just keep going until i apply a little more gas that eliminates the problem and it just smoothly accelerates. it never stalls, never idles rough, never drives rough, shifts smooth and accelerates smooth etc.

so far my diagnosis include replaced TPS, verified thermostat and temperature sensors are working properly, ran with a/c on and off, unplugged mass airflow sensor and drove it on the freeway to see if maybe it was sending bad information. none of these have done anything.

my questions. could it be a fuel issue? or is it most likely my torque converter beginning to go out? if so is there any electrical sensor down on the belly of the vehicle that could be failing due to water exposure? when i first "played around" with the vehicle off-road i went in too deep of water and was in water up to my rockers for 12 hours before towing. for a month or so after my gear selection indicator on my gauge cluster was not displaying anything intermittently. now its working fine again (must of dried out). but now i have this rpm surge that i honestly feel like i noticed right when i bought it, so i dont think its water related.

i appologize for this huge wall of text, but once again, im sure someone on here has had this symptom, and has figured out what it was. i just dont want to get a transmission rebuild if i dont have to yet etc. want to solve the problem without fixing things that dont need fixing ya know?

thanks alot
justin

 

This condition is called torque converter shudder. ~45MPH is the speed at which the torque converter clutch locks up. I bet if you were to just lightly tap the brakes (just enough to illuminate the brake lights), the truck will smooth out at the higher RPM.

This problem can be caused by low transmission line pressure among other possibilities including a bad torque converter clutch (replacement of the torque converter fixes this), worn/weak TCC solenoid, etc.

You may be able to temporarily fix the condition with an additive, but I never like that kind of "fix".

 

youre right on the using of the brakes. i held the throttle steady on the way to work and when it started doing the shudder thing i just touched my brakes enough to make the light come on and the rpms immediately smoothed out and it was the smoothest its ever driven. soon as i let off the breaks it starts shuddering again. does this test suggest a specific problem, or should i still pay a shop to diagnose the issue? is having my transmission fluid changed properly worth trying first?

so far, this is the only issue i have, and the rpm fluctuation is actually not as severe as i thought, it is 100-200rpm at most.

a diagnosis will probably cost me only half hour of labor at my dads shop (cadillac dealership) if it turns out my torque converter needs to be replaced, is there a good brand that lasts longer? i only have 90k miles, seems like a premature failing item like a lot of items on these vehicles lol.

thanks
justin

 

mine acted like this just awhile ago...luckily i just changed the tranny filter and fluid and all is good again.
it was driving me crazy...never thought of something simple.
had tranny shops look at it too...couldnt find a code or anything.

 

alright heres another kicker in this situation. after trying out putting pressure on my brake pedal, (enough to light the lights only) it fixed the shudder and it drove smooth until i let go of the pedal. so that was all fine, i was planning to get it diagnosed possibly.

today driving it home i did the pedal thing a couple times but then i just said screw it and i was just driving and letting the rpms fluctuate. out of nowhere my check engine light comes on. and i have not felt the shudder once now that the check engine light is on. i have even got up to speed and put cruise control on and tried to make it repeat the problem and i couldnt. it drives smooth and normal now. accelerates normal, smooth, it doesnt stall or hesitate or do anything...... only noticable problem right now is the check engine light....

i havent got the codes read yet, im in school. ill get them read wednesday and post what they are. i am kind of leaning towards getting my transmission fluid filter plug all done.

 

If the code that is set is a transmission related code, it could cause the PCM to request maximum line pressure. At max line pressure, the clutch most likely is locking up as it should.

 

ugh, false alarm. the engine code was a mass air meter low voltage, which is probably due to me putting on an aftermarket cai.

and as far as the transmission behavior, either it was a figment of my imagination, or it just decided to behave for a little bit, but it started acting up while i was on my way to oriellys to read my codes.

so im back to square one, i dont know how much it would cost to get my transmission fluid, filter, plug all serviced at my dads shop (cadillac dealer) but certain things i like professionals doing, not because im too scared to do it, but im pretty novice and if anything goes wrong i dont have to pay to fix other stuff. I'd rather have a practice car to work on, i dont have a garage or anywhere to do anything too serious. im sure my dad knows how but i really hate bugging him when hes busy etc. regardless...

i guess i will check my trans fluid dipstick, see where im at, if its full and good color i guess does anyone have a suggested path for me to take? i dont mind doing a tranny flush, but only if it is possible it could help, i mean, flushing it, finding out it didnt help, then going and paying for transmission repair would mean i need to pay for another flush basically.

there any sensors that could have been damaged by me sitting in water up to the bottom of the door (not deep enough to get inside after 12 hours, minus a quarter inch deep, 1 foot diameter circle in the center of the driver floor) that could cause the transmission or torque converter to behave irradically?

at this point, im down to just flushing the trans oil, or paying for a diagnosis and then figuring out how to afford fixing the worst case scenario

 

A problem with the MAF sensor can cause transmission issues. This is well documented by GM.

A CAI should not affect the MAF sensor unless you are using an oiled air cleaner which will leave oil deposits on the MAF sensor elements & can lead to problems over time. If that has happened, cleaning your MAF sensor may be all that is required to cure the P0101 code. Check out the Tech Article (DIY) index in my signature below for a how-to on cleaning your MAF sensor.

 

i want to say the code ended in a 3, i erased it like a moron assuming it was because i installed my cai. P0103 sounds correct which i just looked up and says code P0103 - Mass Air Flow (MAF) Circuit High Input. i suppose i could be wrong, i will document it better if it comes back for sure. also, it is an oiled filter, its just basic cold air intake from ebay, i believe the brand is kool-vue or something. its nothing fancy but the materials seem solid. regardless of any of that, yes it is oiled... should i swap the filter for a non oiled? pretty sure the piping doesnt matter. and my dad talked to one of the GM techs and they suggested unplugging my MAF and it would default it to a general setting, and if the problem went away then most likely my MAF is sending bad information and should be cleaned or replaced. I did this and it didnt change anything other than obviously throwing codes at me. I will definetly look into the article and probably clean it out, it cant hurt and one of little resistor things in there looked a tiny bit darker than the other 2, possibly dirt/char etc (this was prior to the CAI since i had it seperated during install)

on that note, assuming i have to do a torque converter install. I wont even consider doing this on my own personal vehicle with my level of experience. I learn fast, and am not stupid with mechanics, i just dont want to screw up my own vehicle and transmissions are pretty important and expensive when messed up. but my question is, can i get the torque converter out by dropping the transmission or would i have to pull the engine to get it out? my dad can help me with all of this, just looking for tips from anyone who has been down this road.

thanks again
justin

 

check engine light is on again, will get the code read tomorrow while im out running errands. if it turns out my MAF again, any course of action i should persue?