Clonking noises on ICE at low speeds

1. How do you have the time to accelerate to 30mph on ev?

2. Have you changed the spark plugs?

3. You should change transaxle fluid and clean EGR circuit

 

You describe one of the most typical symptoms of EGR circuit blockage, providing the "clonk" is actually engine knock and on the assumption that you're actually accelerating engine on. If you really mean accelerating to 30mph on EV, disregard this entire post.

The service history is great in general, but does nothing to reduce likelihood of EGR circuit clogging. The EGR valve and tube you mention are typically the least involved parts of the 4-part circuit, although cleaning both is necessary. The EGR cooler and EGR ports within the intake manifold usually contain the complete, or nearly complete blockage. Based on your symptoms, you will find this to be the case. If you're not already aware, there is tons of info and how-to's on this forum.

Maybe. But bad engine mounts at your mileage, or any mileage with regard to Prii, is basically unheard of, imo. Engine mounts shouldn't be suspect if you're really accelerating in EV mode.

Well and good, I spose, but this issue can and does manifest to a pretty non-ideal climax with no advance warning lights or code history until late stage misfire, P030x coding. At this stage the knocking will have become much more concerning, and is often the time when head gasket failure is confirmed.

Of course I'd love nothing more than to be proven completely wrong with this internet diagnosis. Best of luck with diagnosis and resolution.

 

Exercise diligence, here. It can be tricky to find a mechanic who can understand the objective, and who will actually take the time to perform this tedious service satisfactorily. Expect a labor charge of at least 6 hours to be able to assume the work was well done.

 

The correct Iridium spark plugs are good for 100k+ miles. No need to get them done at 60k unless you the window cowling removed for another repair.

 

I have the same problem as you, John, just worse. Started at 375k miles (I only use Shell gas so maybe that helped increase how much time it took for the EGR system and intake manifold to clog up) and has been going on till now (460k miles). It has gotten to where you can hear it "clonking" at 60 MPH while on cruise control, even though it normally only happens when driving at low speeds or when the battery is low and the engine is charging it. I also got misfire (P0304 for cylinder #4 and P219A only recently).

Car's at the shop awaiting intake manifold and EGR cleaning, and if not, replacement of the manifold per a TSB from Toyota. Have heard multiple stories of people disconnecting the EGR system to test, and the car ran without any unusual noise (TSB says this happens when the EGR system is active).

Glad to hear your car is doing better. Can't wait to get mine back without any more noise and codes. Then I will have a perfectly-running CT 200h nearing 500,000 miles (that is, after I blew a head gasket back at 375k).

 

Resolution found at this post: Misfire and Air-fuel ratio imbalance | PriusChat