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I've got a 2002 Spec V. A while back I did a rebuild with various parts mostly 2J. It's never ran the same since. From idle to about 3k rpm it has an obvious misfire under normal slow acceleration, it's throwing the P0300 random multiple cylinder misfire, and has occasional back pressure pops on deceleration but that could just be the side exit. It runs great under WOT but does have a smell to it, sorta sulfery, after a hard pull. I had a mechanic plug his snap-on computer up to it and he said either I'm off a tooth or I've modified it to far for the computer to accommodate. If I remember right he said it was also throwing an o2 sensor code which my reader wasn't showing. I'm guessing it was due to my spark plug fouler bung on the lower o2 sensor? He said it was reading rich so the motor was leaning out? Sorry trying to remember everything he said from 3 weeks ago...He was able to advance it 4 degrees which he said helped but I see no difference. I am 100% sure that my intake and exhaust were spot on when assembled but I can only pray that my crank sprocket stayed put. Oh...last thing which could be unrelated is I'm smelling burning oil pretty bad now days under a heavy WOT pull. Do you think this is timing chain related or am I needing a tune? Piggyback? I have no idea I'm at a loss. I've been throwing sensors at it in the hope one had gone bad but so far nothing has helped. I really question the MAF...but don't want to replace it if it doesn't need it. I've read that the aftermarket MAF sensors are trash. Today I spoke with 2 local tuners and they said by the sounds of it I need a tune but they are unable to help me because the uprev wont connect to my 2002. One recommended I call Jim Wolf about some ecu mod, which I'm guessing enables them to connect uprev? I haven't had time to call them yet. Help a brother out.

Here is a list of mods;
QR25 bored .30 over
2007 10.5:1 pistons
Completely removed entire balance shaft assembly
AJUSA head gasket
ebay header with lower o2 sensor spark on a plug fouler
2J Racing rebuild kit
2J Racing Lightweight Flywheel
2J Racing Stage 1 Racing Clutch
2J Racing Lightweight Under drive pulley and Crank Pulley
2J Racing Intake Manifold and cone filter
2J Racing 2.5 inch Side Exhaust
2J Racing High Pressure Radiator Cap
2J Racing 10mm Traction Spacers
Knock sensor relocate
 

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Hi Randy, my name is chris58 and i've just joinedthe Forum.
I can't see on the Forum if you have fixed the problem with your Sentra, but I had a similar problem with my Aussie Pulsar (Sentra) and it turned out to be the 'fuel cut' that the ECU activates, when it isn't getting the correct voltage signal, from the bottom TPS. We encountered a miss then shudder, miss, run, all untill we reached 2000rpm, this went on for 3 years. And we spent $2600AUD trying to fix it. It took an Electronics Specialized Mechanic, 8 mins to diagnose and repair the problem. The car runs like a dream.

I'm waiting for a clearer description from the mechanic that fixed the problem, as I have forgotten the finer points. In my initial hello to the Forum, I described the problem further, but have a feeling I might have some bits incorrect. When the mechanic gets back to me, I'll re post you, if you want.
Chris58
 

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Discussion Starter #5
Im thinking the problem is unrelated. Under a full throttle acceleration, my Sentra flys and runs beautifully. My research is leading me to believe my higher than stock compression pistons mixed with it being bored over, thus increasing my compression even more is my problem. I'm going to be calling Jim Wolf this week.
 

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Randy, it is up to you, but this is how the mechanic fixed my problem, miss, kangarooing, stuttering etc.
The bottom grey plug is the idle contact/change of state.
When the throttle is just open, one wire of the grey plug, will have 0.0v all the time, while the other wire, should see a change from 0.0v while the throttle is closed, and when it is just open, some voltage.
The top brown plug from top to bottom is: the black wire is ground;
Then the yellow wire is variable, with 0.5v at idle, and reading below 0.8v @ 1000rpm.
The red wire should be 5.0v with the throttle closed and at idle, (make sure it is not held open by the damper if installed), Using a digital multi meter on the red wire to earth (motor or battery- not the ECU earth), check for 5.0vs.
It was my Yellow wire, that was reading 0.34v at idle and above, and this voltage signal to the ECU caused the fuel cut to activate. By 2000rpm the voltage was reading just over 0.5v, and the fuel cut stopped.
You can see the adjustment screws at the top and bottom of the TPS, and I’m pretty sure he rotated the TPS anti clockwise, to change the voltage at the yellow wire, higher. From 0.34 to 0.46. With that the problem stopped.
 

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I'm actually having a similar issue with my build. I had to replace my injector pigtail because the 2 cylinder connector got messed up and was causing misfire.

I don't have an efficient data logger. Just that crappy car gauge pro app on my phone, that will only log one event in real time, but it looks as if my timing shifts a lot 3-4 degrees for .5 seconds as I give the engine light load at low rpm before settling at the correct advance. Almost like the ECU has to search for the right value. Not sure if this is normal or not, or if its just an issue with the app.

My plans so far are to make sure my injectors are clean, due to the fact my A/F ratio leans out with the stumbling, and use a step colder plugs. Going to use NGK iridiums.

I am uprev tuned by 2j, BTW. But my tune was done with the old injector pigtail, which could have had a negative effect.

Not trying to threadjack, just sharing my similar experience in case it helps us both find a solution.
 

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I am having a similar problem on my 2005 SpecV, but after trying a bunch of things (too numerous to list), I finally identified the problem and have a workaround in place. Randy's original problem was very similar to mine (stuttering / surging from idle --> 3500 rpm). Chris58's symptoms didn't match mine and I was getting the correct voltage reading on my Throttle Body. I tried swapping the TB (since I had a spare TB) - no change.

I studied the service manual and noted that the O2 sensors control the fuel / air mixture upto 3600 rpm, above that, the ECU's base map takes over completely. I tried swapping the O2 sensors but that didn't solve the problem. So I disconnected the upstream O2 sensor and the problem went away! I don't care about a check engine light at this point.

I still need to figure out why it caused the problem in the first place. Was it faulty sensors or connection or wires??
 

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Interesting.
Swapping the O2 sensors shows they are both OK.
Unplugging the upper sensor, getting a CEL but having it run better seems to indicate the wiring is good as the ECU detects the sensor has been unplugged.

My guess is that there is an leak somewhere between both sensors.
 

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The only thing between both sensors is the connection between the header and the mid-pipe. I replaced the donut gasket before trying the disconnect. No change.
 

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2000 Nissan Sentra GXE
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The engine ground and battery grounds in good shape?

Most manufacturers recommend O2 sensors every 100k.
 

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2000 Nissan Sentra GXE
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Forgot to mention. The back of the intake manifold on the qg18de has a lot of sensor grounds. Make sure their ends aren't corroded and it sits cleanly. I coated mine with a sealant from home depot after I rebuilt my engine. May protect them... may seal water in... I'll find out in a couple years.
 
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