2018 Prius 3 engine vibration on decel and low throttle input

Just bought a decent gen 4 with 81k miles. Drives great for the most part. When you accelerate to speed and then take foot off the throttle 95% of the way and hover rpm just above where the ICE is on, the engine will vibrate if you hold it right above the transition zone. In ev mode and at higher acceleration it drives well.

I was thinking of cleaning intake manifold ports, egr pipe and egr valve and skipping the cooler (it looks like you have to move the inverter)

I also thought maybe spark plugs but AI said it’s most likely not spark plugs because it would show symptoms through the full rpm range and to try cleaning the egr system.

only posting because I saw on here that some people don’t have egr problems even at 300k

coolant was at the low line when I bought it, just topped it off and drove about 200 miles yesterday for the first time.

57 mpg average over the 200 miles.
Edit:

just saw another post where it’s doing the same thing. He replaced his egr valve at just 40k miles. Neither of my scan tools can detect if the egr valve is stuck open. So I need to buy a third smh

I’m going to buy all the gaskets and try cleaning EGR valve. It may be sticking from sitting around on the lot

 

@BiomedO1 this is my thread and I dont have any check engine codes or pending codes.

 

Thanks for taking the time to read and respond. I assumed the PID for stepper motor position would tell me whether the Valve was moving or stuck in one place. I was planning on getting the computer that allows you to actuate the valve while reading the position.

I will move forward with my plan to clean the Intake and passages this evening and take a look at the buildup in the EGR pipe and on the EGR Valve and report back.

 

@ChapmanF Took the intake out, the four EGR ports are very clean. I will still clean them but I’m not sure these are the problem though I was hoping they were.

I took the actuator off and the EGR valve moves easily and springs back to closed no problem.

EGR pipe sooty and dry

Throttle body extremely clean.

After I clean the intake I’ll put it back together and try driving with EGR system unplugged to see if it still shakes.

if it does I will replace spark plugs and coils…

 

alright I put it back together and it’s idling terribly, I know for sure PcV valve is connected on both sides. Not sure if maybe there’s still some intake cleaner in there. Supposed to dry out quickly. Maybe some coolant got on one of the lower sensors from the throttle body drippage.

when I turned the car back on it said ICS unavailable And then when it started it was idling rough as hell. I wonder if my 12v battery is causing issues.

is it possible to put the EGR actuator back together incorrectly? I just popped it off and pushed it down making sure it moved freely.

tried running with EGR disconnected and that seemed to make it worse.

I never tried running for more than 10 second, all I did was back out of the garage.

Looking online it says it’s fairly common to have rough idle after battery disconnect and to try to let the car warm up. I didn’t want to cause any damage to the engine so I didn’t try that yet

 

I can verify this as well at 80k miles the valves are still shiny, throttle body clean and almost no carbon at all in the intake passages. Im kicking myself for pulling it apart now especially since its running poorly. I wish i just did new spark plugs as a good measure, but at least we can rule out the clogged ports haha

 

OK so I saw another post on here where a guy said to run it in maintenance mode for a while and I tried that for about five minutes, but it was still running really rough

I ended up taking it out of maintenance mode and then just backing out of the driveway and as soon as I hit the gas driving forward on the road. The car was fine.

I still have the same vibration, but it seems to be a little better actually and it seems to be running smoother under power as well

it’s idling fine now.

cleaned the mass airflow sensor and I still have the vibration

I’m going to change the spark plugs as a precautionary measure and report back