nirvan4007

What the hell is up..I just replaced my fuel pump due to noises coming from the engine...i replaced it and seems to run better but the noise and shaking keeps on occuring with my engine...... i dont know whats wrong and the shaking isnt viscous but very noticeable....if any of you were faced with this problem please helpp!!

Daniel B. Martin

A bad fuel pump does not usually cause noises in the engine. Did you have other symptoms which implicated the pump?

Prominent engine shake may be caused by a misfire. This could be lack of spark or lack of fuel.

A misfire due to lack of spark will usually turn on the Malfunction Indicator Lamp and set a Diagnostic Trouble Code in the 0603-0608 range. The DTC points to a specific cylinder.

A misfire due to lack of fuel may be caused by a bad fuel injector. This will usually not turn on the MIL.

Sonic

A bad motor mount?

Daniel B. Martin

Your engine miss could be caused by a sticking fuel injector.
There are two tests the home mechanic can make, the sound test and the resistance test.

Sound test...
This test is performed with the engine idling. Use a mechanic's
stethoscope or a length of rubber vacuum hose, and listen to each injector.
All injectors should sound alike. If you find one which makes a different
sound (or no sound at all) you have found a problem.

Resistance test...
This test is performed with the engine off. Use an ohmmeter to measure the
resistance of each injector. This does not require removing the injectors.
I don't know the correct resistance value for the injectors on your model,
but they are typically a low number such as 16 ohms. The important thing
is they should all be equal. If you find one injector with substantially
higher resistance than the others, it is bad. If you find one with zero
ohms (short circuit) that is truly unfortunate, because the injector is bad
and it may also have damaged the Engine Control Module (the computer)
because of excessive current drain.

Measuring the resistance of the front bank of cylinders is easy because the
injectors are in plain view. Disconnect the injector electrical connector
for cylinder #2, measure the resistance, reconnect the connector. Repeat
for the cylinders #4 and #6.

Measuring the resistance of the rear bank of cylinders is almost as easy,
but it is difficult to reach the injectors. The resistance may be measured
at a conveniently located electrical connector. Notice the largest,
thickest electrical harness at the top of the engine. This is the Engine
Control Harness and it is shaped like a U, with the open top of the U at the
driver's side of the car. The U has two corners. Look at the corner
nearest the passenger seat. Just inside that corner you will find an 8-pin
electrical connector. This is connector F131. Disconnect this
connector. Now look at the male part, the connector half with the pins
exposed. They are arranged in two rows of four pins.
The pins are numbered 1 - 4 (top row) and 5 - 8 (bottom row).
Measure the resistance of:
- injector #1 between pins 1 and 2.
- injector #3 between pins 1 and 6.
- injector #5 between pins 1 and 5.
Be sure to measure the PINS, not the female receptacles.

The dealer's shop is equipped with high-tech diagnostic instruments. These are wonderful devices but they are expensive and the dealer has to recover his cost by charging you for diagnostic time. Sometimes the home mechanic can do legitimate diagnostic work with nothing more than a ohmmeter and a rubber tube.

nirvan4007

Thanks guys for all your advice i really appreciate this site its very helpful it helping out all our maximas.....well i made an appointment with the dealership and i did tell them about what might be the problem which you guys listed,,,,,ill see what happens and let u guys know....later