QuestionMy 2001 XG300 was just tuned, it has 117 K miles on it. Diagnostics showed sensors bad, replaced. Car acts like it has a governor on it. Now, trouble code shows P1159, which could be a variable intake motor or fuel system motor OR another BAD sensor...mass air flow? HELP please. Also reading O2 sensors are running too lean on bank 1 and bank 2. Any ideas of what REALLY is the matter? Thank you!
AnswerThe P1159 code indicates that the variable intake won't go to the desired position. Since your vehicle was just tuned, it's possible not everything was reconnected properly or that the key was turned on with the variable intake connector disconnected. First, check all the electrical connectors to the intake manifold and make sure they're properly attached. If they are, clear the lamp and see if the same code comes back. If not, it was probably an issue that occurred and was resolved during the tune up. If it returns, you'll need a new intake plenum.
If both banks are running, lean, then the problem isn't likely to be the oxygen sensors. Again since the vehicle was just tuned, first check to see if the plenum and vacuum hoses were reinstalled properly. If there are any vacuum leaks, that would cause a lean condition. If there are no vacuum leaks, then the air flow readings are probably incorrect. To solve this, you'll need a new air flow sensor.
