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intake leak

Posted by joe_mn (My Page) on
Mon, Jan 18, 10 at 15:30

96 cadillac seville. changed intake due to leak at blow off flap. bad gasket. put on used intake. new intake gaskets. 6 months later i get a p0171 and p0174 code. bank 1 and 2 lean condition. i checked every vacuum line and hose and pcv valve. brake booster too. nothing seems bad. than i got a code p0131, O2 sensor. think these are related? the plenum is dry. no coolant passages to deal with. the intake gaskets are heavy molded plastic with silicone ribs. almost impossible to put in gaskets wrong. attach gaskets. lower intake. how hard is that? i know the torque is low as i cracked the original intake 2yrs ago. any ideas?

Follow-Up Postings:

RE: intake leak

Pull the freeze frame data to identify whether the leak occurred at idle or under a load. (Engine RPM PID and Load Pid, you could even use the vehicle speed as part of the reference)

If it occurred at idle, then a vacuum leak could be at play, if it occurred under a load then a vacuum leak is NOT indicated as a cause.

Once you identify under what operating conditions the failure occurred, driving the car though differing conditions (Idle, part throttle, cruise, heavy throttle) and watching how fuel trim is compensating under those different conditions will be an important piece of information. It's not beyond expectations that the problem could still be a random occurrence. If fuel trim isn't making a correction and there are no hard faults causing open loop, then the problem simply might not be there at the moment.

Lastly using VE (volumetric efficiency) calculations against the MAF sensors reading helps to prove if the MAF air sensor isn't reporting the airflow correctly.
You need to do a snapshot and capture engine RPM, MAF in grams/second, and ambient temperature all under wide open throttle and from there I could calculate the reported VE for you.

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