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Discussion Starter · #1 ·
Hello all, new to the forum and hoping someone has seen this before.
I have searched Google and the forums here, other than generic meanings for the codes ie: intake temp sensor and lean at higher load.

I also read somewhere that the whole intake needed to be replaced?? My car only has 45k on it, was hoping I could do the work instead of taking-it to the dealer if possible.

Thanks for any thoughts you guys might have.

307 Posts
Instead of going into great detail, I'll start off by listing all the possible causes for the codes P2191 and P2199:

P2191 code possible causes:
Faulty fuel injector.
Faulty Mass Air Flow (MAF) sensor.
Low fuel pressure condition.
Faulty front HO2S.
Leak in the exhaust system.
Faulty PCV system.

|P2199 code possible causes:
Faulty Intake Air Temperature (IAT).
Intake Air Temperature (IAT) harness is open or shorted.
Intake Air Temperature (IAT) circuit poor electrical connection.

Visually inspect the related wiring harnesses and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Since you mentioned misfires, here are several things that could cause misfires and set the above codes:
  • Dirty fuel injector(s). Run some good injection cleaner, like BG products 44K, through the system; give the cleaner about a week or two to do it's job.
  • What brand of spark plugs are you using? You should be using OEM NGK plugs; other brands such as Champion or Bosch many times cause driveability problems in Nissan engines.
  • Incorrect fuel pressure. Tee-in a temporary fuel pressure gauge between the fuel feed hose and the fuel rail. The readings at idle should be 51 psi.
  • There may be a major intake system vacuum leak. To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be around 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps. This would relate to what you've read about replacing the intake system where the intake manifold may have a crack in it.

35 Posts
Rogo, my comment was for Barnettworks. Myself? I may throw sparkplugs at it, if no help, then off to a reputable shop or dealer!

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