Constant Misfire but no CEL 96 Maxima

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First, I had P0304 misfire cylinder #4, but no other codes. So I changed out the spark plug for cylinder #4 (using an NGK G-Power, which is the same plug that was in there before), and also switched the coil with cylinder 6's coil. Thank god the misfire is on the front bank!

Now my problem is that it's still misfiring, still constant always missing under 1500 rpm or so. But, the CEL isn't coming back on! Runs and feels the exact same as before, but I'm not getting a code now. What takes so long for a misfire code to trigger? The misfire monitor is continuous, so it's always ready, and a misfire severe enough to damage the cat should make it blink immediately!
 
As a owner of a 98 max, i can tell you this...

1. that OBD system is VERY SLOW.
2. Not every scan tool will show pending faults on that system.

I've used Torque pro for everything and it didn't show up as pending or anything but its was a clear misfire. I even went as far as unplugging working coilpacks of it took a while to read.

Its just how the maxima is.

What scantool are you using, I would recommend you try to get a standalone actron basic ones.

I've chased ones of these down to find out the intake manifold gasket to be bad, it was missing at idle but not at the upper RPM.
 
Some cars are slow to trigger. Take fords for example, they are notorious for not throwing a code for it.
Cars misfire all the time, but it takes a constant miss, that exceeds the preset threshold before the memory buffer runs out.

To do a proper diagnostic, I'd need a scan tool with live data support, or at least mode$06 and watch on what cyl the miss was on. After that I would check for fuel,spark,air,and compression.

I had an ecotec ion roll into the shop with a miss at idle yesterday, and I found cyl 1 had 35psi less than the other three.
 
Since this happens at idle, you could unplug the fuel injectors one at a time. When you unplug a good cylinder it will get a lot worse. When you unplug the bad one, only moderately worse.
 
I wonder if it has to be running for some period of time or temperature before it records misfires.

I have seen that in the past, though not specifically w/ nissans.
 
are you looking at pending codes or not?

anyway to solution to your problem is to buy the new OEM coil and fix it.
 
my 99 max
misfire at idle no cel
mechanic used scan tool sez coil pack is bad on a cylinder
put in one from NAPA - chinese junk napa likes chinese
misfire gone
cel gone for 1 day then back on, no misfire
mechanic got oem coil from Nissan- japanese not chinese
no misfire no cel
this was 3 years ago at 158000 miles
 
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Originally Posted By: Vikas
are you looking at pending codes or not?

anyway to solution to your problem is to buy the new OEM coil and fix it.


Yea I'm looking for pending codes (which I am able to scan for), but even pending codes aren't showing up.
 
Well its spark, fuel, and compression....not too hard to figure out. They did it for years before there were computers and scanners.
 
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Originally Posted By: CBR.worm
That is true, but now computers and sensors control the fuel and spark. And the air in many cases.


However, most of those sensors and ECU's will often cause there to be no spark at all instead of misfires. Especially on a 96 Nissan which is not too advanced like todays drive by wire cars.
 
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UPDATE

The code came back, still cylinder 4 (P0304)

The problem did not move when I switched the coils, so it probably isn't the coil.

I replaced the spark plug, so it's not the plug (although it very well could've fouled, as the end was all black stuff I could scrape off.

Also, there was a small amount of oil on them, and I know the car to be leaking oil, but a new plug wouldn't foul immediately!
 
I would check compression. When you switched coils, did you try switching wires?

If you have good compression (not a burnt valve), and you have spark after trying to switch wires, plugs, and coils, then it leaves you with fuel as the issue. You probably have a bum injector. Just a process of elimination.
 
Originally Posted By: Robenstein
I would check compression. When you switched coils, did you try switching wires?

If you have good compression (not a burnt valve), and you have spark after trying to switch wires, plugs, and coils, then it leaves you with fuel as the issue. You probably have a bum injector. Just a process of elimination.


This car doesn't have spark plug wires. It's a coil-on-plug system.
 
Does that engine have lifters, or adjustable valves? A valve that is too tight will misfire especially at idle. Eventually that valve will burn up if it hasn't started already.
 
Originally Posted By: slacktide_bitog
The engine does not have lifters.

Then you should take the valve cover off, rotate the engine by hand until #4 is at TDC on its compression stroke, and check that all the rocker arms for that cylinder are slack (slightly). If one is still pressing a valve down you need to loosen the screw-- following the specified adjustment procedure of course.
 
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