That tells me the radiator cap is shot.
Tester
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Isnāt 100c kind of high for an ECT sensor to be reading? That makes me think the thermostat might also be defective.
100 degrees C is 212 degrees F. Normal.
Now, if you install a new radiator cap where the cooling system can build the proper pressure, that temp will drop slightly.
Tester
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I feel sure you have a much better handle on this than I do. But it seems counter-intuitive that building pressure will result in a cooler temp.
The original P0171 and āno start when hotā seems to have been dealt with by the new fuel pump.
The latest check now shows the long standing P0507, and now a P0108 has been cropping up. These are coupled with a high idle of 1,100 that pops up to 1,300 occasionally.
You first have to fix the basic systems of an engine before you can try to diagnose codes.
Tester
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Thatās exactly what it does. Why else would all engines run at 15 psi or so?
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The boiling point is increased by 45 degrees.
This maintains the same level of heat transfer up to 45 degrees above 212 F by preventing the fluid from boiling, but this does not enhance heat transfer.
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Iām thinking of home pressure cookers. They cook faster because they cook hotter. Water reaches 250Ā°f in a home pressure cooker, and the pressure reaches 15psi.
Sounds like good advice. I have one on the way.
Your rad fan probably doesnāt even come on until the ECT temp reads 220F, so without the rad cap holding pressure and raising the boiling point, your rad (engine) would boil over every time before the fan(s) ever came onā¦
Air is an insulator. If air is mixed with water as is the case in boiling, then heat transfer is less than when boiling is inhibited. The vehicle cooling system is designed to reach a certain temperature range with liquid water, not with boiling water The temperature of the pressure cooker is different than for a carās cooling system because they have different equilibrium temperatures. You can overheat a pressure cooker if you provide too much heat.
I put on new rad cap on.
Is it possible for a vacuum leak to be present when the engine is running, but not be present when the engine is not running? I refined my smoke machine by adding a vacuum gauge that also reads pressure to 10psi. This enabled me to get the pressure between 1 and 2psi. I turned rhe key on for the test and jammed a stick against the gas pedal to open the throttle, introduced the smoke into the big intake air hose disconnected from the filter housing, and cranked up the smoke machine. I pulled a small vacuum hose and very visible smoke poured out, and then put it back. I kept the the pressure about 1.5psi and looked everywhere with a flashlight, including under the car to check on the vacuum line going to the vapor canister. Saw nothing. Yesterday I pinched off that line before it got to the vapor canister solenoid and there was no discernible change in rpm or vacuum, so I am convinced to a very high degree that there is no vacuum leak with the key on and engine off. The vacuum at idle is 21 psi. I guess the next step is propane, which I will do tomorrow. Now I will go inside and check the service manual for troubleshooting procedure for P0507 for 8th gen Honda Accords with 2.4L engine. Volume 1 is downloadable and is about 3,000 pages long in PDF format: I believe I have addressed all the common possible causes that show up in a search for this DTC.
If a new MAP sensor and a new power steering pressure switch do not correct the high idle, I feel I am being driven to the conclusion that the fault lies either in the wiring to the PCM, or the PCM itself. Thanks to the shop manual posted online I can check continuity of the wiring to the PCM, but if the problem lies with the PCM itself it seems a trip to the dealership would be in order. I certainly cannot deal with it.
Flagshipone makes a great product at a very good price, plug and play for the most partā¦
Flagship One does not seem to do Hondas. 
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Well crapā¦ .
Tomorrow I plan to check some of the wiring for continuity to the computer from parts that impact idle speed. I have two parts on order that are due to arrive Thursday, a power steering pressure switch and a MAP sensor. Both can affect idle speed if faulty. If they do not correct the high idle, and the wiring is in good shape I am led to believe that the engine control computer could very well be at fault. I am all but certain that there are no vacuum leaks, but I will do a propane test tomorrow as well. This test is good for when the engine is running. The smoke test I did again today can only be performed when the engine is off, and that did not reveal any leaks.
Yep, but thanks for the heads up.
Donāt give up yetā¦ lol
Someone might post a place stillā¦
I learned that with a "pass-thru Vehicle Communication Device (VCI) I can use Honda software to reprogram the ECM to recognize the closed throttle position.
