Hi all, I am new to this website as I created this account to ask this question. I can't seem to find someone else who has had this exact problem with a Civic of this model. There are plenty of tutorials on fixing an RPM surge at idle(an IAC valve issue), but none on a surge while driving at cruising speed (35-50MPH). It started today, as I was leaving work for lunch. I was going about 40MPH and suddenly the engine started revving up and down intermittently while my pressure on the gas pedal remained constant. I could feel the constant change in acceleration. It was somewhat nauseating, honestly.

I was wondering if any of you seasoned Honda guys have seen this before and what you'd guess the problem might be. I am praying that it is not a transmission going bad, and I would love to hear that my fears of such a problem are nonsensical.

So far, I have found several possible solutions, but I can't attest to whether or not they'd make a difference:

Dirty throttle body - Run Seafoam or otherwise clean the throttle body
Low Trans Fluid - Replace or refill with genuine Honda ATF
Clogged EGR valve - Clean or replace
Bad MAF sensor - Replace
Low refrigerant levels causing AC compressor to cycle on and off - Add R134A

Which one of these methods, if any, should I try first?

To be considerate of others having the same problem, I will keep this thread updated if and when a solution is attempted.

Thank you in advance.

 

Update: I checked trans fluid, it was at the correct amount and was light pink in color.
I also tried driving with and without the AC on, that didn't change anything.

 

does it also idle up and down ?

 

Nope, only when I'm moving in 1, 2, D3 or D4.

EDIT: I dropped it off at Honda today, as it started leaking transmission fluid. Will update with what they say.

 

It turns out that a seal on the front right CV joint was nonexistant, causing a strong transmission fluid leak. They found a cracked brake line as well. Also, fun stuff, my engine block is cracked and the extended warranty ended 9 months ago - before I had the car.

 

Your best bet is to drop in a JDM replacement. They are not prone to the engine block cracks like the USDM variant is.

 

You're right about the swap for JDM. If it weren't so expensive I would go that route. After my car is made road-worthy again, I've been thinking of trying something called K-Seal as a last resort. Supposedly it works pretty well for small block cracks and general coolant leaks. I hope the crack doesn't compromise my ability to push the vehicle to 200k+ miles, as I need it to last that long.

 

yes, i used kseal on my 06 civic and it worked well

​​​​​

 

That's good to hear! It should come in on Saturday.

The car got back from Honda today, and it seems the shifting is back to normal! Thankfully it was just a leak from the axle.

 

they got k-seal at most auto parts stores, comes in a square quart or so sized orange and blue bottle

drain about the same amount and add it in in the radiator when the engine is cold, start it and let it idle til it starts up and the leak should be substantially lower, but not completely gone