A 96 Maxima recently came into my care. The Check Engine Light was on
when I got it. Codes (0304 Knock Sensor) and (0302 EGR Hi/Low Flow)
were stored in the ECU. The car had 130,000 miles on it. No "blow-by"
from crank case, no smoking and not consuming oil. It had an
intermittent "pulse" or misfire when in drive and stopped. Idle in park
was smooth, unaffected. Light throttle produced power surges and until
you stomped on the gas it was difficult to get it to any speed. When
trying to accelerate from 30 to 60, power was non-existent until you
pushed the throttle so hard the transmission would kick-down into 1st
or 2nd and nearly redline the motor. Attacking the knock sensor first,
I checked the resistance. It was completely open, no resistance at all.
I put a new knock sensor ($120.00) in. I checked the EGR valve by
sucking on the hose and felt the diaphragm raise and hold without
leaking. I assumed it was functioning, assembled the parts and reset
the ECU. The symptoms remained unchanged. The (0304 Knock Sensor) code
never returned. The (0302 EGR Hi/Low Flow) code did return. So I put a
new EGR valve in. After removing the old one, I inspected it closely
and saw no reason for it to malfunction, but I replaced it anyway. When
I was installing the new EGR valve, I noticed the supply pipe from the
rear exhaust had some exhaust debris in it. I removed a small piece of
debris and assembled the parts not giving it much thought and reset the
ECU. This also had no effect on my issues, the symptoms still remained.
I decided to check fuel pressure and compression. Both tests were
perfect with little to no deviation from specs. Attacking ignition
components, I started with spark plugs. When I pulled the old ones out
they looked fine, but they were the cheapest plug you can buy- $1.99
Champions I think. 6 new Nippon Denso's ($7.99 a piece) went in. I
noticed the rear bank coil packs had burn marks on one side of them. At
the time I did not know for sure they were burns because they are so
close to the intake I thought they could have been scuffs from rubbing
and vibration. It did not appear that the front bank coil packs
suffered this problem. Using my Fluke I tested the resistance of all 6
coil packs across all terminals. All 6 coil packs seemed to be really
close to each other with no huge deviations. The test was inconclusive,
so I re-assembled the parts. The new spark plugs had a small effect,
the "pulses" or misfires were fewer, but still present. I considered
the rear bank coil packs with burns on the sides as my prime suspect.
With the engine running, in drive, park brake set and hood open, I got
out and looked at the coil packs in complete darkness (Dont try this at
home!) and saw the unmistakable blue colored arcing to the intake
manifold, which wraps tightly around these high voltage devices. This
would explain the burn marks. New coil packs went in the rear bank. 3
ignition coils @ $70.00 each...ouch. Again, I reset the ECU. The surges
during acceleration dissapeared, and taking off did not require heavy
throttle and harsh kickdown revs to make it move. But the "pulse" or
misfire at idle was still there. Half of my problems had dissapeared.
The (0302 EGR Hi/Low Flow) code came back shortly after. With nothing
left but intake seals as suspect, I decided to put new upper and lower
intake manifold gaskets in. When I took the EGR piping off I discovered
a lot more garbage was clogging the line than the little piece I pulled
out previously. The new EGR valve had some collected in it as well. I
found the plenum was severley clogged with carbon and deposits where
the EGR pipe dumps it in at the rear of the intake. Both EGR pipes,
upper and lower manifolds and throttle body were thoroughly cleared of
build-up and cleaned. New gaskets for the intake upper and lower,
Throttle body, EGR were installed. After re-assembling the intake
system, I again cleared the ECU. Bingo!!! The "pulse" or misfire was
gone, and never returned. The throttle response and smoothness were
dramatically improved. All of my problems were resolved and the car is
a pleasure to drive.

After enjoying a Check Engine Light-Free Maxima for a few days, the
damned thing lit up AGAIN...........(0302 EGR Hi/Low Flow) code. I
really doubt there is any problem with the EGR system. The engine is
running fine. Smooth and responsive throttle and with no misfires.

The only thing I can think at this point is a bad 02 sensor. Looks like
"njmodi" is suggesting the TPS of the MAF may be bad also.

Does anybody have any suggestions?

Please Help!!! -Adam

Check the O2 sensor with self diag and/or dmm. Should be Fluctuating 1V to 0V.

ECU drives EGR solenoid, Check the voltage level at the valve... simulate tst valve functionality. If suspect, tst swap wiring/hoses with pwr solenoid.

Brittled vacuum hoses?

My guess on this intermittent problem is oxidation, low voltage at ECU etc... groundings, connectors needs tune up. Start from charge voltage checks, at batt, at ECU. Clic p14, see link below.

The symptoms dont directly point to TPS/MAF...

Btw. 'No danger' in car electronics: you may die only if u swallow the batt. (too big box). Possibility to cause Fire and/or short damage to ECU are real...


--
Wiikinki
www.cardomain.com/ride/748507/1
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adupyours wrote:



EGR temp sensor got damaged. The blockage you describe is a -very- comon
problem with these cars.

--

Steve

http://www.atlantaracing.com

Steve T wrote:

I noticed the negative terminal on my battery was covered in battery
acid, so I put in a new battery and new ground cable, covering the
fresh connections with protective spray. I have also cleaned many, if
not all, connections including the PCM or ECU connectors, next to the
gas pedal. I am sure now that I am not dealing with connectivity
issues. Even after doing this

The EGR Temp sensor... Is the little sensor on the flange going to the
intake, with 2 22-24awg wires going to it? I was very careful not to
damage these little wires, but anything is possible. How do I check it?

Thank You! -Adam Orlando, FL

adupyours wrote:

Not sure of the number of wires but it's the sensor in the EGR pipe. I
thought it was a 1 wire sensor..

FSM will tell you how to test, I don't have one handy.


--

Steve

http://www.atlantaracing.com

...revved the engine and pushed the EGR valve
open with my finger. Almost immediatley, the DMM read 0.8 volts. This
would explain why I keep getting an 0302 EGR Hi/Low Flow code, the EGR
valve is not opening! Okay, maybee somebody is laughing at me right
now, because it turns out that the problem is the EGR Control Solenoid...
Somebody???

I am laughing cause I told you to check it, tst swap wiring/hoses with pwr solenoid... Verify my txt above. Bingo.


"Almost immediatley..."
EGR temp sensor measures coolant temp at one point. Affecting coolant flow (like revving) will affect coolant temp at this point, and its measurement reading.

However, exhaust circulation -or- its ctrl doesnt affect coolant or its measurement. Its totally different entity. Thus pushing EGR valve controlling gasflow, cannot affect EGR coolant temp sensor reading.


--
Wiikinki
www.cardomain.com/ride/748507/1
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Wiikinki,

I think you are mixing up the ECTS (Engine Coolant Temp Sensor) with
the EGR Temp/Flow sensor. The EGR temp/flow sensor does not come into
contact with any coolant - and doesn't measure coolant temperatures.
The EGR temp sensor is located in the EGR guide tube that runs from the
EGR valve up to the upper intake manifold. It detects both flow as
well as the temperature of the recirculated gas. The ECTS is what
measures coolant temp and feeds that info to the ECU.

Cheers,
Nirav

njmodi wrote:
Much Thanks to "Wiikinki" and "Nirav".

"Wiikinki",You were right about telling me to check by swapping with
the power solenoid, but I had no clue that you were refering to the
other two valves located near my faulty one. After checking all 3
solenoids I understood their specific function/flow and how swapping
them would have identified my problem. I do not work on cars every day,
my specialty is electric forklifts, and their parts look a little
different from car parts. But that is irrelevant. I simply did not
understand what you were saying about swapping the valves, so it is an
error on my part. But you were right, and I will admit it! And for that
I thank you. Unfortunately, I'm just not as sharp as some!

"Nirav", thank you for your input. You are correct about the temp
sensors. The EGR Temp sensor never comes into contact with coolant,
although coolant does flow near it where the EGR pipe meets the intake.
The EGR pipe going to the intake has a flange/casting where it meets
the intake, and the EGR temp sensor is mounted in the side of this
flange/casting, drivers side. Similar to an 02 sensor case/casting
style, it is about 1/8" in diameter, about 1" long and has two little
24 or 26 guage black wires going to it.

When I was revving the engine, the voltage did not fluctuate... only
after opening the EGR valve with my finger did it drop. After releasing
the EGR valve the meter returned to 1.7 - 1.8 volts. This verified why
the code kept coming back, and why the voltage never dropped to where
it is supposed to.

So I have just bought a solenoid from the Nissan dealer, and going to
install it. Hopefully I am remedied of that *damned* 0302 EGR code!

Adam - most likle the solenoid will take care of your problem. You
have taken the time to correctly identify the root cause rather than
take the "throw parts at the car" approach. Don't feel bad about
cleaning the EGR guide tube - that is most often the cause of the 0302
code. The only other cause I have ever seen is the solenoid (that you
are replacing). Unfortunatley the 0302 code can be caused by so many
EGR components, you have to troubleshoot each component seperately to
isolate the root cause.

I had the code not too long ago (a year or so). Cleaning out the guide
tube and plenum port cured it for me.

Cheers,
Nirav
96 Max GLE, 130k

Well, I just took it for a test drive after installing the new EGR
Control Solenoid. I monitored the voltage at the EGR Temp Sensor during
this test. ECU has been reset of course. The voltage now drops to 0.1
volts for brief periods and varies from 0.1 to 1.2 volts while driving,
mixed conditions. Steady around 0.47 volts at 40 MPH and about 0.35
volts at 50 MPH. Voltage slowly returns to 2.0 to 2.2 volts after about
90 seconds of idle and drops steadily when accelerating. Longer
accelleration times cause larger voltage drops and short accelleration
times produce smaller voltage drops, proportionatly. Once a steady
speed is maintained, fluctuation is less than +/- 0.04 volts. It
appears to me that the system is functioning perfectly now. I also
noticed the "Spark Knock" the car always had has all but vanished. I
knew it could be potentially harmful to the motor, but I always
adjusted my accelleration to compensate. Not any more.

I sure hope it stays this way! It has kicked my butt for a while now.

Again, many thanks to everybody who responded!!!

-Adam