I tried search but only found the question posted by 03Atls but no reply to same issue I am haveing.
"Does anyone know what this means - When i drive at a constant speed around 35mph with steady gas the tach will move up and down about 100rpms. Any help would be great. Thanks"

i am haveing the same issue its if i hold gad at any speed 40 60 70 , and i can feel or hear the engine rev up.....and after driving aroun 20 30 milesconstantly it eventually stops occuring.. any idea..
anyone.. thanks

 

Motor mounts ?

 

auto or manual? bc ive read a post a while ago that it could be the converter locking up at higher speeds not sure the exact detail on what was happening to that member but his rpm would also drop and raise a bit while driving

 

sounds like vacuum leak to me whats it do at idle

 

My car had your symptoms a couple months before having trans issues.
My car you could just barley see the rpm needle move up and down but,you could feel the car feeling like it had a slight surge.
Driving the car everyday I noticed,some might not if they don't drive it everyday.

I check for vac leaks and could not find one. Then I thought of changing the tps but it did not help.
Then p0740 a couple months later.

 

isnt that the CAT code ?

 

tcc malfunction.
Lock up problem

 

sounds like torque converter lockup.. a manual couldn't do this anyway unless the clutch was slipping.

 

yeah sorry guyz its an auto cls... sorry noob question. How to check VAC leak and so what did you ended up doing to fix the TCC problem..

 

Visually inspect vacuum lines .Make sure they are connected,not rotted or split. Questionable hoses you can spray some carb cleaner while the cars running,the engine should stumble if a leak is sprayed.
Your symptoms sound exactly like mine did and if it happened to me again the first thing I would do if their was no vac leak or bad tps would be drain the trans fluid to look at it.
I'm not done trying to fix the tcc problem yet. Well not sure.My cel and tcs are off now so hopefully I did.
You probably don't have any lights yet huh ?
I didn't till one day cruising at 65 and the trans started slipping in and out in a rhythm similar to what it sounded like your sound is now just more progressed damage.
Next thing I noticed after the noise/rpm rise was the the car was getting less and less predictable off the line.Like sometimes it would light the tires all day and sometimes it would feel like the car need more of the cars power to move like the trans was periodically adding drag,then the shit on the highway.
Hope the same shit is not going to happen to your ride.
I would check your trans fluid and get it clean.That's about all you can do if it's the trans and you don't have any lights yet.

 

you'd have a high idle tho if you have a vac leak most likely. and u'd hear a pretty decent sound from under the hood.

from what u've said tho it sounds like the car runs fine accept for this one thing.

with my first trans that happened to me. ur most likely lookin at tranny work.

 

I have the same issue!! Rpm jumping a little bit while at a steady cruise at 35-40-45 mpg Ive been having it for about four or five months now. Ive taken it to some transmission shops because I thought tranny right away, being automatic and everything, but they couldnt blame it on the transmission.

Went to the dealership for a test drive and my tech said he felt nothing that he could blame on the transmission.He told me its possibly a clogged EGR port. Its possible, my car has 168,8XX miles on it.

It hasn't gotten worse, even with some WOT runs. I want to clean the EGR port to check if thats the problem.

Which I havent gotten around to doing yet.

 

I have an idling problem as well on my car. I just wanted to know if u could have a tranny prob with the tranny shifting smooth and fine.

 

^most likely a vaccum leak or iacv

 

^^ x2 on that

 

Its not the iacv, because i cleaned it last weekend. now i'm gonna check for vacuum leak and probly seafoam it on sunday. because its annoying.
I already change spark plugs
change engine oil
change tranny oil
seafoam the gas tank
2 bottles of gas treatment .

Called the dealer and they want to charge me $125 for a diagnostic. and i aint having that.

 

sometimes cleaning the IACV is what causes the idle to go all wonky..\

did this happen before or after u cleaned it?

when u unplug the iacv what happens? any significant change?

 

All I can say is since I've replaced,and cleaned all sensors,and changed fulid on my trans mine does not do the rpm rise while I'm at low speed cruises anymore.
100% truth there.

 

the fact u cleaned the IAC OP doesn't mean it's working, or is not malfunctioning

if that were true then no one would buy an IAC when there is a problem they'd just clean it and problem be fixed.

but it just doesn't work that way.

heck even cleaning it can cause a bad idle to spawn out of nowhere, i've seen that before too.

 

That's so tru. I've seen people clean it and still have prob. So I think I will replace it if the seafoam doesn't clear up my problem. Do u guys think a broken axle boot could cause this prob. I will be changing. That this weekend. Thank for y'all help and sorry for thread jackin. Didn't want to create a brand new thread if we having the samme prob

 

i have exactly the same symptoms & i think its the IAC valve. just looked up the part its a crazy 100 bucks....

seafoamed 3 x in 1 month no help.

here is my own troubled link 4 ref

 

dont see no link

 

for sure its not gonna be an axle boot

 

check your t p s

 

the link is the here is above.

 

so i am going through all the things mentioned above but I am also noticing extensive gas consumption by the engine. It seems like i am barely getting 20 on highway and 10-12 city and so far only rpm jumping i feel while trying to hold certain speed, so far no lights on dash. I am worried now since cant pinpoint the problem ...