My Honda Accord (2004) was giving me a P2647 error code. Replacing the VTEC solenoid solved the problem for about a year, then the issue of bucking and lurching whenever the car hit ~2800 rpm’s returned!

Note: is reader-supported. If you buy through links on this site, I might earn an affiliate commission – at no cost to you (Amazon makes less because a small % goes to this website). Thank you for your help keeping this site active!

In an attempt to fix the problem I performed an engine flush with Liqui-Moly Engine Flush. The following is the procedure I used. I have not had the bucking problem or the P2647 engine code since.

Tools and Supplies Used:

  • Engine Flush. You’ll need a bottle of engine flush in order to do this (duh), There are lots of options out there, the one that I use and recommend is Liqui-Moly Engine Flush. I assume there are other good brands, I just haven’t personally tried those.

Also important to note: You will need to perform an oil change once you are done with the flush! So, have the following supplies ready as well in order to perform the oil change:

Procedure to Flush the Engine

The first step is to read the instructions on the can of Liqui-Moly carefully. Basically you just add the entire bottle to your engine oil, start the car and let it idle for 10 minutes, then turn off the car and change the oil.


Get your oil change supplies ready so that once you’re done with the engine flush you can drain the oil and replace with fresh oil and filter.


Remove the oil filler cap.


Open the bottle of Liqui-Moly…


…and pour it into the engine oil filler port.


Replace the cap. Start the vehicle and let it idle for 10 minutes.


Turn off the car and perform an oil change. Here is what my oil looked like after draining it out. It was quite dark, though hard to tell if darker than normal. Also I did not necessarily notice any sludge, but the Liqui-Moly is a solvent, so what it dislodges it likely also dissolves.


It has been approximately one month since I performed this engine flush, and I have not had another experience of the car bucking and lurching when the RPMs hit ~2800 or so!

I will continue to monitor the situation and update if necessary.

Thank you.