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P0108 Loss of Power

I just bought a 2005 Honda Odyssey from a car auction on Tuesday and noticed it was losing power going up a hill. I hooked up my code reader to it and it spit out a p0108 code. I then replaced the MAP sensor but is still doing the same thing. I think there might be a vacuum leak somewhere. Does anyone know what might be the cause? It has a 3.5 vetec engine with 170k miles.

That’s a lot of miles on an engine, but a well-maintained Honda is capable of many more. My 1999 Civic is over 174,000 miles now and runs great.

Every time I’ve changed plugs on my Honda, I have adjusted the valves. There have always been several that needed adjusting. Valves not working right can on their own cause loss of power. I’d do that first, then do a compression test, dry and wet. If the plugs are non-OEM or of questionable condition, put new ones in at that time.

The way it works on my Corolla, there’s three pins that connect to the MAP. The two outer ones have 5 volt reference applied to them anytime the key is “on”. One is ground, one is 5 volts. The middle one is the output of the sensor, which varies between that range. I forget how it goes, whether high vacuum is a high volts out, or the other way around. Anyway the way I tested mine, I applied vacuum to the MAP sensor with a hand held vacuum pump and measured that third pin while I varied the vacuum. If it changes more or less smoothly in the 0 to 5 volt range over the 0 to 25 inches of vacuum range, the sensor is probably working. It’s a pretty uncommon thing here for a report of a failed MAP. They’re pretty reliable parts.

You could have a problem with the connections between the computer and MAP, so make sure you are at least getting the 5 volt reference at the connector to the MAP. Don’t throw the old one away btw, a MAP sensor makes for an excellent home-brew barometer or altimeter.

P0108 doesn’t mean that the MAP sensor has failed. It just means that the sensor is reporting a voltage that is outside of what is expected during normal operating conditions. For example, plugged exhaust can cause a low manifold vacuum. The MAP sensor then reports that low vacuum to the engine computer, who then says “Hey, something’s not right.” and turns on the check engine light. You need to find the cause of the low engine vacuum reading.

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I was kinda worried about that. I just don’t know if someone poured liquid glass in the radiator or not. Could that cause issues of this nature?

It looks like the previous owner poured AlumAseal (liquid glass) in the the radiator, which could only mean one thing…a cracked header. Could that explain the P0108 – Manifold absolute pressure (MAP) sensor/barometric pressure (BARO) sensor -high input code that I got and the loss of power?

A cracked head (not header) or head gasket could cause low vacuum and low power. A compression test, and comparing readings to those of adjacent cylinders, would provide more clues.

I dpon’t think the alum-a-seal stuff would affect the MAP sensor one way or another. But if it was used to forestall some major engine problem, perhaps it isn’t working. And the code is indicating the intake manifold vacuum isn’t as high as it should be. That’s would definitely cause loss of power. DIY’er vacuum gauges are inexpensive and easy enough to use. A properly running warm engine’s intake manifold will generally measure in the 15 - 22 inches of Hg range at idle. If the MAP sensor’s diaphragm leaks, that could cause this symptom too. That’s easy to test with a hand held vacuum pump, Mighty Might MityVac I think is the brand name that makes a lot of them for the diy’er market.

The company is mityvac

Given the fact that the engine was doctored before being sent off to auction tells me that someone knew there were major issues so they chose to just gum it up and dump it at the sale barn. Not an uncommon procedure… :-(.

It may be losing power going uphill because the engine is fried. I would strongly suggest that a dry and wet compression test be performed to determine what (rough…) shape the top end is in. If the compression is down then you need to throw in the towel or consider another engine.


My buddy is going to check into it. He does alot of rebuilds. If the engine is not salvageable I am prepared to look at other options thank you everyone for your expertice. I will keep you posted with what the outcome is.