I gave my 95 GLE (129K) to a local Nissan dealer for lots of regular maintenance (e.g. transmission, cooling, & tune-up). I got the car back with what seems to be a skip at idle (w/ the car in gear and my foot on the brake at a stop light). The hesitation also appears at 35 to 40 mph at about 1200 RPM. All of this occurs only after the car has warmed up (5+ minutes).

The dealer couldn't find anything wrong, until I took a technician for a drive. Then, their analysis concluded that it was one or all of the following: front oxygen sensor, rear oxygen senson and knock sensor. Having lost all confidence in this dealer (there were a lot of other problems), I took it back to my regular guy. He confirmed that it was not any of the sensors (which would have cost $948.55). After five hours of trouble shooting, he concluded that it was an idle motor. $564.79 later, the problem persists.

Another symptom that hasn't been properly diagnosed, yet, is a cold start problem. When the outside temp is below 40 degrees F, and especially when it's wet/damp, the Maxima requires some pedal to start (i.e. it turns over, starts and dies immediately if I don't give it some gas). It's had this problem for a while, so I don't think it's related to the new hesitation problem.

Between the Nissan dealer and my regular guy, I'm out $900 and my car is far worse than when it went in for service.

HELP!

 

From what I understand if the car starts hard in cold weather it is probably an injector problem.

 

well, is there any engine codes? if you have bad O2 or knock sensor it should throw a code. if it doesnt you may have what we call a lazy O2. (cycling slowly) i forget the spec but its .1v-.9v
whats an idle motor? maybe IACV?(idle air control valve)

O2 sensor shouldnt cost you more then $60 each. The IACV was $90 i think when i replaced mines, but my ECU threw the code so i knew it was bad. good luck man, dont let people BS you.

 

The Engine Coolant Temperature Sensor sends a signal to the Engine Control
Module (the computer). When the ECM gets a "cold engine" signal it directs
the fuel system to provide a rich mixture to help with starting. This is
similar to the function of the choke on a carbureted engine.

Your symptoms suggest that the ECTS has become inaccurate and always sends a
"warm engine" signal to the ECM. That's okay when the engine already is
warm but causes hard starting when the engine is actually cold.

With the engine cold, disconnect the ECTS and measure its resistance.
Reconnect the ECTS, start the engine, run it until fully warmed up. Stop
the engine, and repeat the resistance measurement. The "warm" reading
should be a much lower value than the "cold" reading.

The Chilton Maxima shop manual gives these specs:
Engine coolant temperature 68F, ECTS resistance 2.1 - 2.9 Kohms
Engine coolant temperature 194F, ECTS resistance 0.24 - 0.26 Kohms
(Roughly a factor of ten difference.)

The ECTS is a relatively inexpensive sensor and something the home mechanic
can replace without special tools.

 

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.

Electrical 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.

 

Can anyone recommend a good fuel injector cleaner?

 

This was my first experience with this web site, and I must say that I am an extremely satisfied customer. Thanks for everyone's help. Dan Martin, thanks for all the time you put into my problem. That was very kind. I'm not much of a mechanic, so I'm going to pass on all the comments to my mechanic.

Regards,

Mike Rasmussen
Groton, Massachusetts