OBDII code P0410 and bad fuel economy related??

[Volvo850Bob]

Hello,

I have been looking over this site and found it very helpful, yet only hints at the possibility of my problem and no concrete solution from which I can fix it. I drive a 1997 850 GLT and my problem is the recent development of poor gas mileage. By poor I mean going from 25 mpg on average to around 15 mpg within a week. Considering the cost of fuel these days this is devastating to me and my wallet. The only thing I can tie to the cause of this sudden drop in fuel economy is the recent 'check engine' light. After going to Autozone to see what was causing the light to come on I found that it returned an OBDII code 'P0410' which refers to 'THE PCN HAS DETERMINED THAT A MALFUNCTION EXISTS IN THE SECONDARY AIR INJECTION SYSTEM' After talking with my father about the problem he said it was just low airflow to the catalytic converter which was nothing to worry about. However, it apparently is something to worry about due to the significant decrease in fuel economy. After doing extensive research on a multitude of forums primarily including this one with bits and pieces from elsewhere I have come to a couple conclusions. One: this is tied in with the O2 sensor that apparently causes bad fuel economy or Two: there is a possible vacuum leak associated with the air pump. This could possibly explain the gas-guzzling effect due to a heavily fuel rich fuel/air mixture. I don't know if these two conclusions are related to each other, though I wouldn't be surprised, and I don't know what my options are especially due to already scraping the bottom of the barrel for cash. If anyone can help me with this by providing some options/solutions/etc. I would be extremely grateful.

Below is an outline to give the barebones symptoms, effects, and hypothesis I have come up with.

Car: 1997 Volve 850 GLT

Symptoms:

'Check Engine' light illuminated registering an OBDII code of 'P0410' -- 'THE PCN HAS DETERMINED THAT A MALFUNCTION EXISTS IN THE SECONDARY AIR INJECTION SYSTEM'

Effects:

Decrease in MPG by near 10 (average - 25, recent average - 15)

Hypothesis:

1: O2 sensor bad? causing poor fuel economy (fyi - I don't know where to locate this sensor or how to remove/replace it)

2: Vacuum leak associated with Air Pump causing a heavily fuel rich fuel/air mixture? (also do not know where I would look for a vacuum leak or the air pump)


I apologize for my lack of knowledge of these cars, I have already learned alot on my own and I know with Volvos that one should learn how to repair them yourself to get the best value out of them. I am very eager to learn how to repair my car for two motivations: one being of course the money and the other just out of the desire to learn about my car.

Someone please throw a lifeline ...

Thanks,

Volvo Bob

[White850Turbo]

Air pump problems are a known trouble spot on these cars. My car doesn't have one thankfully, but I can give you advice based on what I've read elsewhere. The 2 most common problems are broken/leaky vacuum hosing and a faulty SAS valve. It sounds to me like the problem is a tear in one of the hoses. The air pump doesn't run all the time, which can make diagnosing it rather difficult. Here is a diagram of how the air pump is set up. In the diagram, you can see several vacuum elbows. They are labeled 17, 18, 22, and 26. These things are infamous for breaking. Inspect all of them thoroughly and make sure none of them have broken or have holes in them. Be sure to check all of the other rubber hoses associated with the air pump also. Another thing, be sure to check the little vacuum elbow directly down and behind the power steering pump, that hooks into the intake manifold. It is also infamous for breaking and causing bad gas mileage. I wouldn't mess with your o2 sensor until it throws a code. Check those elbows though and let us know what you find.

[Volvo850Bob]

Thank you for replying. I have checked as much of the vacuum lines as I could reach and have identified connections 17, 18, 22 and 26. 17 looked considerably degraded and even if it isn't the cause of the problem I would want to replace it anyway. 22 also was a bit on the rough side, but 26 and 18 looked fine (provided I correctly identified them. I wasn't able to see the connection behind the power steering pump, which I will keep on trying to find as I do more research on where the power steering pump is located and if I can actually get to it without taking too much apart. I will update that as I find out more.

Another quick question, how much do these vacuum elbows go for?

Thanks,

Volvo Bob

[Jot]

With an unlit propane torch turn on the gas a move around the engine which needs to be running. any leak will show up with an increase in engine speed