Highway Acceleration


#1

On highway, at higher speeds (50-70), I notice that the vehicle’s acceleration will pause and the rpms will bounce a bit. Best description I can give is that it feels as if someone were constantly pinching and releasing the gas line. Short revvv…revvv…revvv. The vehicle doesnt lose power. I get where Im going. And it only occurs up at these higher speeds.
Any thoughts why?


#2

This is a duplicate thread by the OP. See the thread (RPMs Vs Acceleration )

@mfa Having multiple threads about the same problem reduces your chance of real help.


#3

No. It is not duplicate.
Rpms are involved, but two different issues.


#4

How old is the vehicle? Make and Model (need this for potential common problems). There could be several causes.

I don’t know if I can help, but I suspect you’ll get a lot of different opinions. You may need to bite the bullet and take it to the shop to at least diagnose. Combustion failures are usually logged in one way or another on the computer.

You could have a misfire, you could have a clogged catalytic converter (check for glowing at night), you could have a mechanical problem in the valve-train (engine type is important), you could have a fuel delivery problem… MAF Sensor… MAP Sensor…

I could go on and on… :smile:

Maybe with a little more information I or someone else could better advise.


#5

Its an 02 Chevy Trailblazer. 111k miles. Autot trans.
I wish I could describe more. Thanks.


#6

It doesn’t matter that there are two different issues. They are likely linked to the same problem.

Consider your issues as symptoms. Like an illness, you get headaches, muscle aches, nausea, etc… Just because nausea is different than a muscle ache doesn’t mean you have multiple illnesses, right?

I would suggest updating that thread with the additional symptoms. It may turn out to be a separate issue, but then it may not. The transmission responds to various different engine conditions, and the valve body regulates flow channels…

If you use one thread, you’ll get better responses with more accuracy. Right now, anybody that reads one but not the other won’t have the right information before them. I didn’t really notice that you had posted another at first.


#7

possible a clogged fuel filter, and/or fuel pump is getting weak.


#8

Could be a worn throttle position sensor (or throttle pedal sensor), could be a worn throttle body, leaking intake gasket, cracked vacuum hose, dirty transmission fluid. failing transmission, bad ignition module, worn spark plugs or wire.

Any or all of this stuff might be causing this. Is the cehck engine light on? What’s the code it set? Does the engine have good compression?

Without more information it is impossible to diagnose over the interwebs.


#9

Based on info from the other thread my guess is the torque converter clutch is flaky, or it’s the bands (clutches really) in the transmission.
And I agree this is at least a parallel if not duplicate thread.


#10

My best guess goes w/ @circuitsmith , some kind of transmission related issue.

After that, something gone wrong in the throttle system.


#11

I would guess the bands are slipping. But I agree that the TC lockup clutch is a good possibility too.
The threads are related, although the OP may not realize it.

Question to the OP: have you checked your tranny fluid level and condition? Follow the directions in your owner’s manual to check the level, and to check the condition wipe the tranny dipstick on a clean white cloth. If it smells burnt, and/or if it’s pitch black, that’s a bad sign. Post the results.


#12

“Question to the OP: have you checked your tranny fluid level and condition?”

Both Circuitsmith and I gave the exact same advice, yesterday, in the OP’s other thread, but there is no report back from the OP…so far…about what he/she found when checking the trans fluid.


#13

Perhaps the third time will be a charm. :smiley: