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Hi all, my car is a 1996 Nissan Pulsar. The engine runs fine through the colder months, but the last two summers it's had a problem with missing. It only happens when the outside temperature reaches about 28 or 29 degrees celsius (previous summer it was ok in the low 30s and I took it to a workshop but it ran fine that day and they couldn't find a problem).

It only happens under load, eg normal acceleration in traffic, or when you start driving up an incline. It's often a bit random but the hotter the weather the more consistently it happens. After the sun goes down it usually drives fine again in the cooler evening.

When it misses there is a kind of clicking sound, I don't know how to describe it.

Replacing the following things did not change the problem:
-Spark plugs, tried NGK and Bosch
-Spark plug leads
-Fuel filter
-Distributor cap
-PCV valve

Any ideas would be appreciated :)
 

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One of the first things to do is perform an ECU code readout with a portable scan tool to see if any fault codes are set. The tool can be purchased at most auto parts stores or from Amazon.com. Post the actual codes here on the forum so that we may be able to help you further. If there is one or more fault codes set, they can help point to the malfunction. If you have a copy of the FSM for your vehicle, the code readout procedure is described there along with a listing of codes. You can download a copy of the FSM from this web site: Nissan and Infiniti Service Manuals or Nissan Service Repair Manuals. The section EC.PDF is the one you need to read.

Several things that could cause misfires:
The camshaft position sensor may be marginal. It's been known to fail due to varying outdoor temperatures. The sensor is located inside the distributor.

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 as follows:
  • with vacuum hose connected to the fuel pressure regulator: 34 psi
  • with vacuum hose disconnected from the fuel pressure regulator: 43 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 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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