Been wrestling with P0440 codes for a while. I've replaced the gas cap and many questionable vacuum hoses but to no avail. More recently a P0171 (fuel mix too lean)and P0172 (fuel mix too rich) have been added to the P0440 code. After re-setting the codes, now I only have P0440 and P0171 codes. Any ideas?

Haven't checked the vacuum lines near the fuel filter yet. That and a smoke test seem like prudent things to try next. I actually replaced the MAF about 7 months ago after I had some intermittent stalling with a few cylinder mis-firing codes. That fixed the issue at the time and those codes didn't come back. For the P0440 code I was thinking about replacing the EVAP valve - haven't swapped that out yet. Or should I focus in on a possible manifold leak first?
Thanks! Steve

If you are close to a Volvo dealer, you could call him and make a free appointment to get the codes read. They have more specific codes that can point to the EVAP valve if that is the problem.

First, check the lines next to the fuel filter. If the filter is original, replacement isn't that hard. I can talk you through it if you want.

Klaus
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Did you do your Random Act of Kindness today?

Thanks for all the insight into these codes. I had an independent repair shop just replace my fuel filter this past August along with a tune-up. However, they did not work much on the vacuum leaks since they lacked a detailed vacuum diagram reference. I just found a disconnected vacuum hose under the injector rail. Replaced with new vacuum hoses (with splicing to accommodate different hose dimensions) but not sure of integrity of connections. Engine performance drastically improved, but after resetting check engine codes, codes still came back (P0171 and P0440). The vacuum diagram I have shows that vacuum line going to a “T-PIPE PCV”. Where is the T-PIPE PCV and what does it look like? Any recommendations on sourcing the long plastic vacuum lines used for routing vacuum between the manifold and back of the engine? Also, I inspected the short rubber hoses (vapor return line) near the fuel filter. These are original and look very dry and cracked. Dealer wanted $35 + $25 for OEM fitted hoses. Any recommendations on sourcing plastic vacuum fittings to step from one size hose to another to avoid purchasing dealer replacement hoses? I'd like to replace all the questionable vacuum connections before paying for a smoke test. What is the best source for a clear detailed look at the vacuum hose connections and routing?

The p0440 almost needs a smoke test. Did you check the lines close to the fuel filter?

Your too lean/too rich could be a manifold leak or possible MAF problems.

There was a Saffron for sale close to me with only 215K on it. Owner mentioned something about needing a little body work, so I passed.

Klaus
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Did you do your Random Act of Kindness today?