Volvo: code p170, mass air flow meter, mass air flow

Question
QUESTION: They say that my engine is running lean is this true...I've lost a bit of power it seems and the engine is not running as smooth. It seems to want to cut out at 4000rpm. What shoul i be looking for?

ANSWER: Serge,
Not sure of the year and model of your car. I would get the system tested and repaired before bigger problems occur.

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QUESTION: Sorry about the missing information...It's a 1996 850 turbo wagon, and i've also notice to happen at other speeds and rpm's
Thank you!

Answer
Serge,
You have a fuel trim code. That is control unit not being able to set fuel mixture. Fuel trim codes come from vacuum leaks intake, exhaust leakage, bad Mass air flow meter, improper fuel pressure, leakage from canister purge valve, engine oil contaminated with fuel. I have seen many Mass air flow meters go bad. Try a known good one to see if that helps.