cold start knock/rattle fixed

Hello, new to the forum, but have read a lot of threads during my search of my problem with the Prius V. My wifes 2013 Prius V we purchased new, it has had all maintanance done at the local Toyota dealer since new. It has 149,290 miles on it, uses no oil in between oil changes, and has had no problems until this winter, when it developed the dreaded cold start knock/rattle within the last month. I read a lot of the posts about this problem and watched many videos including the one by nutzandbolts?? I am very mechanically inclined and decided to tackle the EGR system and intake manifold cleaning myself as I cant see paying the dealer what they would charge to do the job.
So yesterday I tore it all apart, and started cleaning the buildup out of everything. it wasnt really too bad for the mileage, but did have the milky oil sitting under the throttle butterfly. The cooler was the worst of course, so I corked one end and poured lacquer thinner in it and let sit overnight. The manifold I could see had some build up in it, so I got a tub and filled it with hot water and Dawn and let it soak several hours, then dumped and repeated.
I then pressure washed both this afternoon and was happy with the outcome, so then started putting it all back together. I did make note that my manifold is the newer one, 17120-37054, so Toyota's claim that a new manifold will solve the problem is not true. After several hours of reassembly and refilling the coolant (I chose to drain the coolant from the system to avoid clamping all the lines and still loosing some when the lines were taken off), I got to the point where its like, OK, lets start er up and see what happens.
I am working in my shop where its 55-60 degrees, so not really a cold start. I start it up and still have the knock/rattle/rough idle, just not as bad or loud. I pushed on the gas pedal slightly to see if that would help, and it was very non-responsive. I then try pushing it more, and more, and was like dang, this aint good, it barely revved up.
It seemed like it was only running on 2 cylinders, so I pulled all the plugs out so I could compare them to each other, as if one cylinder was not firing, the plug would be wet, or black. But all the plugs looked the same. So now I am baffled and need some insight on what to try next. I cleaned the EGR valve and just reinstalled it. Can someone tell me if these symptoms would be from the EGR valve not opening or closing when it should? I took it apart as much as possible and cleaned it and with the solenoid off, i could push it open and the spring would push it closed with no problem, but maybe the solenoid is bad? Needless to say, I see no way of telling if the EGR valve is opened or closed while its running, and not sure when its supposed to be in either position.
Or did I miss doing something I should of? or forget to plug in a sensor? I checked many times to see if I got them all, but them buggers can hide really well sometimes. Luckily I waited to put the cowl/wiper assembly back on, so its not in the way if I need to get back in there.

 

Just to give some more info, the wife drives the car 5 miles to and from work. The cold start knock/rattle is happening every day now, started out just being a time here and there. It hasnt been run for less then a minute and then sits over night like most people are saying when it happens. Oil level is fine and looks clean, antifreeze is not going down, this should rule out a head gasket? the car is parked in the garage every night, and the garage is under the house, so it hardly ever gets below freezing in it.

 

Whats the part number of the newer egr valve? I couldn't find that in my searches.

 

Well that's the number on my get valve. I did take it apart, all except taking the spring clip off to remove the plunger.

 

Egr valve, darn auto correct.

 

Put new plugs in the car and got the belly pan cover deal put back on and took the car for a,ride and it ran great. I parked it in the barn so I can test a,true cold start tomorrow morning and see if it acts up.

 

Car started and ran great after being in the cold barn all night. So can I change the title to problem solved?

 

So here is my theory on what's causing this problem. The egr system design is faulty, which causes carbon buildup thru out the whole system, including the spark plugs. But the rattle/knock cold start and rough idle on cold start doesn't appear until the spark plugs get carbon buildup on them causing misfired on 1 or more cylinders. So a quick fix would be to clean or replace the spark plugs. But unless you clean the egr system, its just a matter of time before the plugs get carbon buildup again. So cleaning the whole egr system and the plugs, or replacing the plugs is the long term solution. Like my original post said, this just started happening on our Prius this winter, after 149k miles.

 

Just to clarify, our 2013 Prius V has the newer 25620-37120 egr valve and the newer 17120-37054 intake manifold. So not sure if these most recent designed pieces allow 149k miles before the problem arises compared to earlier versions have the problem much sooner?