Engine shudder on slow take off

It is a big job and ideally the head is machined in the process. See this video

 

PriusChat thread, by @The Critic :

2011 Prius Head Gasket Failure | PriusChat

 

Hi Guys,
I’m having exact same problem as the OP after trying everything mentioned on this board. New spark plugs, intake manifold cleaned out, throttle body cleaned out, entire EGR cooler/pipe cleaned and blasted at the carwash pressure washer. Replaced PCV, i had replaced just one coil while troubleshooting the misfire and moving the coil doesn’t change the codes, so ruling out the coil as the culprit. Replaced all fuel injectors.

I was aware of the Head Gasket failure and was losing coolant very very slightly and having the morning rattles. And random low speed shudder as explained here. I had used BAR’s LEAK to temporarily fix the problem and it did FIX it for a couple thousand miles. So, found a mechanic who was willing to work at home to help with replacing the Head Gasket. I ordered the FEL PRO kit. Also replaced the Timing chain and water pump and thermostat. Did an oil change and flushed and refilled coolant with Toyota Long Life. The car immediately threw the p301 code. And low speed shudder. Other than that drives like brand new. Did a compression test on all 4 cylinders and was all good. The Head has been to the shop prior to installing it. Now, I do not know what else to do to get rid of the low speed shudder (misfire).

Note: prior to the Head Gasket replacement, had P300, P301, P302, P304. Random Misfire in those cylinders. Now its Only P301.

it’s a 2011 Prius with 190k miles.

Any insight would be greatly appreciated. Thanks!

 

Leak down test? Guessing the new head gasket is compromised, there’s scoring on head or block, something like that.

seems to me workflow for diagnosing your orig symptoms should START with leak down test; rather than all the coil, injector and PCV overtures. And definitely not a coolant sealer product.

with the sealer: you may be able to flush it with 50/50 water vinegar. Get some more sealant, add to fresh coolant in a jar, let it jell, then test with the vinegar/water, see if the jell dissolves.