wyche89

I was trying to refrain from posting for as long as I could, but after trying the typical solutions, this problem is baffling and frustrating me. Alright, let me give you a little history on my car. I put headers on my car, and didn't install an O2 sim for a while (just recently installed one). There was no rush for me in putting in an O2 sim because I figured it wouldn't do any harm other than an annoying SES light. Whether it's related or not, I don't know, but now I have P0300 code, which is a random misfire. I replaced all the plugs with NGK platinums and gapped them correctly at .44" I tested all of my coils, and they all seemed to test strong (I'll post the results soon). I tested all the fuel injectors and they all tested between 13.5 and 17.5 OHMs. I tested for a vacuum leak, and the reading is 19HG at idle, which is normal. I also have a new 5th gen MAF in there with the IAT sensor from my old MAF.

Symptoms:

• P0300 SES light
• Poor performance (slower than normal)
• Rough idle
• Outstanding gas mileage (32 highway MPG)

Next to try will be the knock sensor, I suppose. Anybody else have any other ideas?

zero2sixtyZ

iTrader: (30)

In for interest. I have the same code, and haven't done as many tests, but replaced sparks, MAF, coils, etc.. Still haven't found the answer.

wyche89

Oh I'm not the only one? lol.. thats cool.. i can't wait to fix this problem man, cause i'm running like high 14s at the track and i REALLY shouldn't be.. do you have the same symptoms as i do?

Blitzfist

iTrader: (2)

32MPG and your complaining? Sounds like you could be running with a cylendar not firing at all. that would cause rough idle and possibly good gas mileage.

wyche89

oh, i'm not complaining about the gas mileage.. lol.. i'm complaining about the poor performance.. i threw the gas mileage in there as an extra clue to help figure out this problem.. now how would i go about testing to see which, if any cylinders are not firing?

rroderiques77

iTrader: (45)

I would have used Iridium plugs in lieu of plats. Did the misfire code take place after your "tune-up" or after the headers were installed? I get the infamous PO300 from time to time. I've got headers, intake, exhaust, etc.
As far as the rough idle, did you adjust your AFR upon installing headers? If not, you might want to tune that beast as you are probably running rich. Also, did you do the idle relearning procedure properly?

wyche89

well i figured i'd go with the stock plugs to be on the safe side... the misfire code was there after i put the headers on, waaay before i put the plugs in.. i went to a nissan dealer to have the idle reset after i did the tuneup, and it was still rough.. i do plan on getting tuned in the future, but even on the stock tune, it should not be running like this

knight_yyz

iTrader: (40)

I had the same problem, changed my plugs, and coils and neither helped me. Then I bought Aaron's phenolic spacers. The problem went away. i think I had a pinhole leak in the crappy rubber coated gasket between the plenums, or the elbow and the plenum. Either way there must have been a pinhole leak and switching to the phenolic spacers with the RTV sealant finally worked. I'm not saying it was because of the spacers. It was the crappy gasket which was replaced.

zero2sixtyZ

iTrader: (30)

Great, possible justification for power mods... sweeeet.

wyche, I have the light and the gas mileage. When going to the NWP meet back in Sept., I averaged 31-32 mpg, but didn't think much of it though.
Performance, I haven't noticed a difference in, and the idle seems to be fine, but I have the ES motor mounts, so there is always a bit of vibration in the car when stopped.

I made a thread a while back, but the IM theory could be possible since I had an SSIM done. I did OEM sparks like you, OEM coils, and even then, I'd imagine it could narrow it down to a cylinder. The random misfire thing makes me believe its something before reaching that far creating a hiccup.

wyche89

yeah, if that was the case for my car, then it would have showed up on the vacuum test.. my vacuum pressure is still within normal range at 19HG

zero2sixtyZ

iTrader: (30)

Bump, interested in anyone elses findings...

wyche89

indeed

have you tested your fuel injectors?

rroderiques77

iTrader: (45)

It sound like you may have a leak at the LIM or UIM. This would cause a poorly running condition.
The PO 300 is a random multiple cylinder misfire. As weird as it may seem, I get this same code from time to time and have 0 driveability issues. You may have two different problems.
Reseal your intakes with Aaron's spacers and you should fix the 1st problem.

louie2k3

i had the same problem....i changed my coils, maf, and plugs..then i put my headers with no o2sims and the code popped up...installed the 02sims and no codes

Ahmad_1290

iTrader: (2)

My p0300 comes on and off. It came on for a while after i changed the plugs. Comes on and off, its annoying

zero2sixtyZ

iTrader: (30)

I have not. I was contemplating having them done by http://www.deatschwerks.com

wyche89

you know you can test them yourself with a multimeter.. to get to the back middle one, you gotta rip of the IM though

wyche89

Ok, I tested the knock sensor, and it tested at .561 and .567 OHMs when I switched the positive and negative rods between the 2 pins on the knock sensor. So how high is the voltage supposed to be? The haynes manual says it's supposed to just measure continuity, but make sure the OHM meter is capable of measuring at least 10 OHMs because it's supposed to measure high. What's the voltage on a normal knock sensor, and could this be causing my misfire code and poor performance?

boris

The KS failure is a common problem with 4 gen, you can get a lot of info if you search there.

Ahmad_1290

iTrader: (2)

If it was the KS, wouldn't it throw a code for it?

SixSpeedA33

A KS wont typically throw a light unless its signal or power supply is missing. Any incorrect values it sees, it will interpet as a misfire or knock and tell the ECM to retard timing. Just a side note, if your getting 29-30ish MPG your motor is probally not misfiring, MPG would go down because of wasted (unburt)fuel in the combustion chamber being blown out the exhaust.

wyche89

well the code was still there soon after i did that highway test for my MPG, and my car is still slower than it should be

wyche89

thanx for the tip.. i did some searching in the 4th gen forums, and i saw that one guy tested his knock sensor, and it tested fine at 14OHMs.. so maybe mine is too weak? i dont know.. does anybody else know how many OHMs the knock sensor is supposed to read?

zero2sixtyZ

iTrader: (30)

I completely forgot about my timing!!!

I used to have the AutoEnginuity setup w/ Nissan Interface and advanced my own timing. Before this issue, my base timing was 15degrees, which I upped +2 to 17degrees.

I remember trying to do it again, after many months while the misfire was prominent, and it was at a default of 13degrees, which from I could only advance to 15 as a max.

I'm not sure if this is directly related, but I figured it might help in the search.

wyche89

i doubt if a timing advance would have anything to do with it... i got my timing advanced (after the first one was erased) after many months of this misfire, and the guy was able to adjust it to 17* i want this crap fixed man, i'm tired of my car being slow! lol.. my boy has an extra knock sensor i'm gonna try today.. keep your fingers crossed for me fellas

Ahmad_1290

iTrader: (2)

man.. i hope thats the problem. I'm sick of misfiring too.

boris

Ignition off
Disconnect KS wiring harness
Check resistance between terminal 2 on KS and ground for 500-620kohm

This is the quote from the 4gen forum. Unfortunately, i can't tell if it's the valid resistance for 5 gen too.
You can temporarily replace KS with simulator (a resistor with corresponding value) to see how this affects the performance. If hard pinging occurs, it means your KS just doing its job (loss of power feels).

zero2sixtyZ

iTrader: (30)

I was mentioning my timing change from default 15 to default 13. Based on what SixSpeedA33 said, the KS would retard the timing...

wyche89

ok, i tested my boy's knock sensor and it reads .567 ohms.. with the leads switched back and forth on both of the pins.. that still seems low though, but i don't know what it's supposed to be.. the haynes manual says above 10 m ohms, one guy on here says his tested good at 14, another post says 500-600 kohms, which i'm assuming would be .5-.6 ohms, and would make mine good... confused... i need to go to a nissan dealer to see if i can test a brand new one

anybody with a functioning knock sensor wanna be kind enough to measure the ohms on theirs for me? lol

wyche89

hey man, i think i figured it out.. it was the knock sensor.. i replaced it with a used knock sensor and i got my top end power back, and the misfire code is gone.. howvever i still have a rough idle.. it might be my IAT sensor code thats causing that though

try a knock sensor and see what you come up with

zero2sixtyZ

iTrader: (30)

Try doing the relearn for the idle. Are you running an 01 maf? How much is a KS and how hard is the install? I really hope this is the cure.

Edit: just reread your first post. If you can invest in the AM600 03 MAF.

Ahmad_1290

iTrader: (2)

I did the idle relearn thing more than once.. i doubt it'll help. I've still got the p0300

zero2sixtyZ

iTrader: (30)

I was suggesting the relearn for his rough idle.

Ahmad_1290

iTrader: (2)

ohhh. gotcha

wyche89

i don't know if that would help, because it's only rough some of the time... sometimes it's smooth, and sometimes it's rough.. kinda weird.. worth a try i guess though

a brand new knock sensor is a little over $100.. and not hard to install.. it's kind of a tight squeeze between the 2 banks of the IM, but you can access it from the drivers side of the vehicle.. if you have a stock intake, you'll probably need to take that out though.. once you get around the intake, you can fit a ratchet and a 12mm deep socket in there to get it out.. and BE CAREFUL cause there are some sharp edges in there man!! my hand got cut up a little bit

as far as MAF, i aint payin $400 for a brand new one.. lol.. i'll either buy just the IAT sensor online, or find a cheap 5.5 gen MAF on ebay or a junk yard

M@XiMus

Had the same issue with P0300 code now for almost 3 weeks...I took it to a local mechanic and they first told that i needed new spark plugs so i got those changed and problem went away only for a couple of days...Issue came back with same code..>Then, day before yesterday, bought all new ignition coils and replaced them all..>Cleared the codes and been driving now for a whole day now without that code coming back. Hope thats solved but since i changed the ignition coils i now have a P0335 Crankshaft Position A Circuit Malfunction....WTF!!! Could those two be related or just coincedence that once came after the other...I got the recall done back in 2004 for that same sensor..Does anyone have any similar or know of any info on this

Professor

iTrader: (4)

been having the misfire issue also.

Ahmad_1290

iTrader: (2)

Can a camshaft position sensor cause a random misfire I've gotta recall on mine

KRRZ350

iTrader: (29)

Wyche89, you've got 200k on o2 sensors that are good for 80k if that, replace the primary o2's, that's my .02cents.

MaximusMorpheus

iTrader: (3)