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Discussion Starter · #1 ·
First car started to idle rough, got the code and put a used ignition coil on which fixed it. When replaced them I kept the old ones. Have not had the a/c off in many months in Florida. A few weeks ago if gas was slightly above 1/4 tank if you hit the throttle it would bog down like no fuel. Put a new fuel pump on. Then the car started to idle rough between 250rpm to about 600rpm and would put in neutral when stopped at a light. Check engine light came on P0133 which is bank 1 upstream o2 sensor. Replaced it and also put new spark plugs in. Erased code and did a relearn on ECM. The car still idles like it did before. I put a new Hitachi throttle body on 2 years ago. Could someone please give some help on what the problem could be. I have a feeling the check engine light will come on again showing P0133 like it has the other times. My old 02 sensor was a new Nissan when I changed it it had a white powder on it. I am lost.
 

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Admin and Sup Mod keeping the peace
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Several things that could cause misfires:
  • Is the misfire occurring on any particular cylinder? 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.
  • 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.
  • 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 51psi
  • Leaking fuel injector(s). A good way to test for leaking fuel injectors is to Tee-in a temporary fuel pressure gauge between the fuel feed hose and the fuel rail. Turn the ignition key to the run position but DO NOT TRY TO START THE ENGINE; wait 10 seconds, then turn the ignition key to OFF. The fuel pressure reading should be around 51psi which would be a static reading. Now watch the gauge; if it starts dropping down fast, that's an indication of a fuel injector(s) leak.
  • Bad coil pack. Did you replace just one coil pack or all of them.
  • The cam position sensor may be marginal.
  • 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 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.
 

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NF Mod/Nissan Master Tech
2006 Pathfinder LE, 2003 Frontier SVE
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You might want to check for a blown head gasket. They aren't uncommon on the 1.8L and would explain the white powder on the O2 sensor.
 

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Discussion Starter · #4 ·
The only problem with the car is the idle. When you accelerate the car runs very smooth. You can go 10mph at a consistent speed, you can go 80mph at a consistent speed you can floor it and it has a lot of power and just goes and the engine is smooth. It's not running lean anymore. My throttle body came with an IAC when I bought it. Then again code P0133 bank 1 o2 sensor slow response. I took a video with my phone but the file is too big to upload
 

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Discussion Starter · #6 ·
Took my car to the Nissan and had a diagnostics run on it. It's the air intake manifold gasket. They also recommend replacing the "0" rings where the injectors go into the head. The gasket cost $19.99 and I already have some new "0" rings and will replace both. The diagnostics cost $96 and is money well spent. Get my gasket in the morning and then will do the repair. I can do it in around 3.5 hours if I don't stop but will take my time and do it in 4 to 5 hours. Will let you know more after test drive. Makes sense since the car has a lot of pickup and power it just acts like it runs lean and my next move was to rebuild the injectors. I usually takes longer to scrape and clean the old gasket area than it does to take it apart.
 

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Makes sense since the car has a lot of pickup and power it just acts like it runs lean
Yep, a small vacuum leak will generally affect the idle more than higher RPM's. They may have diagnosed it by looking at your A/F-alpha (STFT on most generic scanners). Small vacuum leaks will always cause a rich STFT that goes away above about 2000 RPM's. It's a dead giveaway. Usually unmetered air won't cause a rough idle, but the plenum gasket is an exception. A leak there will generally affect the cylinder right beneath the leak more than it affects the others, causing what may feel like an intermittent miss.
 
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