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View Full Version : P0300 Random/Multiple Cylinder Misfire - should i worry??



RaysurX
03-05-2004, 07:59 PM
Got the code pulled today....

Came up under normal FWY driving and I didn't go WOT or drive hard up to when the light went on that morning.

1) Is it "somewhat" normal for that code to throw because of the finicky ecu or have any of you gone onto other problems after this code appeared?

2) Has anyone troubleshooted the cause to date?

BTW - I have NO performance mods installed (yet). And drive the EVO fairly tamely....

alfredob1
03-05-2004, 08:02 PM
1) I've gotten it once. No problems before or since.

2) Cleared the code no prolems so far.

I have the Xede and a cat-back.

Evo Neil will be able to speak from experience.

Howie
03-06-2004, 01:42 AM
what kind of gas do you use? I seem to get it whenever I use cheveron or Mobile. Shell is ok... and I never get it with 76. I was in a hurry on wednesday, so I just filled up with Cheveron... 50 miles later... CHECK ENGINE LIGHT comes on. I just filled up with 76 tonight.. i'll let you know if it goes away.

Cr0mster
03-06-2004, 01:55 AM
I always get it with 76. I stick to costco and Shell now.

alfredob1
03-06-2004, 02:02 AM
I too use mostly CostCo gas, Arco when I can't make it to CostCo.

Howie
03-06-2004, 02:09 AM
is costco gas good? i wonder what the difference is..

Cr0mster
03-06-2004, 02:12 AM
In my opinion its great. I have had no problems at all on it and its a good 10-12 cents cheaper than anywhere else.

ChuTHIS
03-06-2004, 03:04 AM
bad experience w/ cheveron? i always thought cheveron was good gas, but then again my check engine light has come one twice already, never got a chance to scan it though, but now that kinda makes sense...

DocMortal
03-06-2004, 04:10 AM
Weird I always liked mobil but get this,Mobil here by my house in irvine fill it up go to work check engine...tried chevron by my house same thing 76 same thing...one day I filled it up the exxon /mobil station in santa monica where I work,no check engine light...seems even though the stations are the same they differ,my evo loves gas just from that station in santa monica..........untill I find something better in the OC..

Also the PO300 code is a problem in our evos nothong to worry about,In my opinion it has to do with the fact we have the worst gas here in CA,so we have to deal with the pesky PO300 code.......

Dr. Evo
03-06-2004, 11:30 AM
Arco gas is water...."bottom of the barrel" from gasoline distributors. They buy it cheap, and that's why they can sell it so cheap.
The P0300 code is probably caused by a bad spray of fuel and is nothing to worry about unless you experience drivability problems (ie. misfire of bucking, etc.). I have heard talk of looking into it, but it probably won't happen unless there is a huge rash of cars setting them.
As far as just letting the code reset, OBD II works like this: A code such as this on will set with 1 occurance. Most codes take 2 "trips" to set a code. Once the code is set, it takes 40 key cycles without the computer sensing another problem to turn the light off. Just because the light is off doesn't mean the code is not still in memory. Another group of "drive cycles" is needed to clear the code. For a P030..code this is ok, but some codes while they are set cause the PCM to trim back fuel and sometimes go into limp-in mode. I would say if you get a light, have it cleared with a scan tool. BTW don't pull the battery cable to clear a code (you lose all your fuzzy logic learned data). Any generic OBD II scan tool can read/clear a code on '96 and later cars. Just thought I would help :D .

Dr. Evo
03-06-2004, 11:32 AM
BTW... any concerns or ??'s you would like addressed? I will be attending more factory traing soon and the instructors are a wealth of knowledge. Also, I run into Mits engineers sometimes, so let me know!

ItsStockOfficer
03-06-2004, 12:07 PM
I run 23 PSI on pump gas and 12.2's on pump....Love my Arco ;)

Howie
03-06-2004, 12:33 PM
BTW... any concerns or ??'s you would like addressed? I will be attending more factory traing soon and the instructors are a wealth of knowledge. Also, I run into Mits engineers sometimes, so let me know!

Yes.. we would like to know if a dp or exhaust will cause the Evo to Ping.. as stated in this thread:

http://www.socalevo.net/forums/viewtopic.php?t=1397

Thanks!

JanSolo
05-23-2004, 07:31 PM
The Official Word from Mitsu.

http://www.norcalevo.net/gallery/albums/album110/PO300.jpg

GokuSSJ4
05-24-2004, 11:34 AM
an Jan how many Evo owners do you think use racing fuel :wink:
its sad to see that they state anything to not cover under warranty. Robi has posted before that running all type of different gas brands and he has still come across the problem. I use chevron all the time and no problems what so ever.
An my car is fairly stock :wink:

leaveit2bevo
05-24-2004, 01:18 PM
My car has only had 76 except for the 104 fuel at the EOC and no CEL ever

GokuSSJ4
05-24-2004, 04:39 PM
what about the previous event at SOW running 100 octane, i guess some Evo are more sensitive then others.

leaveit2bevo
05-24-2004, 05:33 PM
nope my car has never thrown a cel

perversity
05-24-2004, 05:51 PM
Mitsu are suggesting that the P0300 is caused by the knock crank position sensor being too sensitive and throwing a code at High RPMs. Having said that, other members who have taken their car to the dealer with the p0300 problem have had the plugs, coils and plug wires replaced to resolve the problem. Personally, if it were me, I would get all of the ignition components replaced under warranty.

GokuSSJ4
05-24-2004, 05:58 PM
i know that running high octane like 100 and also leaded fuel will get your spark plugs dirty , were you either clean them or replace them.

STiTHIS
05-24-2004, 06:24 PM
are you at stock boost, 19.5?

Nebolic
05-24-2004, 06:35 PM
A member is being offered a new "Ecu Flash" from a Mitsubishi Dealership (Sacramento) in the upcoming week. Apparently, Mitsu has a new flash to fix the P0300 code. Will keep you guys updated once it goes through. It should happen real soon, and we'll let you guys know.

Nebo

racespex
11-29-2006, 01:53 PM
just got an 03 evo .and having the same prob. code p0300 its driving
me crazy..so nothing i can do to get rit of it ??? please help thanx..

kipper215
11-29-2006, 02:03 PM
just by a creader that will stop the error from happening.

kipper215
11-29-2006, 02:04 PM
flash does not work. I already had it done.

racespex
11-29-2006, 02:19 PM
what is creader??

trinydex
11-29-2006, 02:21 PM
device that shivnu tuning sells for their xede.

racespex
11-29-2006, 02:25 PM
how can i get 1..sorry im new to this but i love my evo.. i been trying everything
change ..spark plug. wire.. tune up ..bring to 1 of speed shop out here in vegas
they dont know whats the prob.. is..any more info..will help me out alot ..thanx you so much..

BHCevo
11-29-2006, 02:27 PM
My stock evo started exhibiting this problem over and over again. It was a real problem. Power loss when it happened etc...

When I got a harmon motive reflash it went away. This is the same P0300 "fix" that dynoflash has implemented.

I'm not necessarily recommending dynoflash or reflash ...just saying that it did fix my P0300 problem.

You can always get your car reflashed with stock timing and fuel maps...but with the P0300 fix added to the ROM. Just email your ROM image to dynoflash and tell him you want the P0300 fix added thats it and negotiate a nominal fee. If its less than $50 then I don't know how you can go wrong its too cheap not to try.

kipper215
11-29-2006, 03:37 PM
you can buy a creader off of EbayÂ* O0

http://cgi.ebay.com/ebaymotors/CREADER-OBD-2-II-ENGINE-CODE-OBD2-OBDII-SCANNER-READER_W0QQcmdZViewItemQQcategoryZ43989QQihZ002QQi temZ4626456298QQrdZ1QQsspagenameZWD1V

alan678
11-29-2006, 03:52 PM
funny....my car just threw that code yesterday as well...first time ever and i have had my car for 2 years/28k + miles....what kinda gas are you using??? I am on shell...

trinydex
11-29-2006, 06:39 PM
dealership can flash the p0300 fix too but results have varied. i honestly was hoping that since i hadn't heard of this in so long that it didn't exist anymore. turns out i guess that's not the case.

racespex
11-30-2006, 07:56 PM
been trying everything but not thing work.. reset it a few times.. but it still come back on.. change spark plug, wire. tune up.. will try diff gas.. and maybe octain booster..too see if it work.. will up date..

trinydex
11-30-2006, 11:10 PM
its an ecu thing ur not gonna fix it til you flash... that's like looking outside your house for something you dropped inside.

racespex
11-30-2006, 11:11 PM
i had a guy reset it for me a few times.but it keep coming back.. is there a thing call
p0300 flash???

trinydex
11-30-2006, 11:13 PM
dealership can flash the p0300 fix too but results have varied. i honestly was hoping that since i hadn't heard of this in so long that it didn't exist anymore. turns out i guess that's not the case.
do you read?

you need to stop posting in a whole bunch of different places in the wrong forum about the same thing when people keep telling you the same thing. if you want to fix the problem, you must fix the problem. doing lots of other stuff that doesn't fix the probelm, does not help you or us.

racespex
12-01-2006, 12:07 AM
sorry..

G20
12-01-2006, 12:10 AM
since your car is basically stock, you can visit evom and get an ecuflash file for the stock 03 with p0300 fix and try it on your car to see if it "fix" the problem. Just make sure don't drive it too hard until you "feel" good about it.

Pops
12-01-2006, 12:30 AM
how can i get 1..sorry im new to this but i love my evo.. i been trying everything
change ..spark plug. wire.. tune up ..bring to 1 of speed shop out here in vegas
they dont know whats the prob.. is..any more info..will help me out alot ..thanx you so much..


I don't think you want one.... Shivnu put one on my car and I probably missed some very important codes - and my engine blew up . It will just erase all codes so if you are getting an important message, you might not see it.

Try gapping down your plugs; .022 - .025. If your gap is too big, you can misfire.

EvoVIIIGSR
05-02-2010, 09:34 AM
I know I'm probably attempting to revive an almost 4 year old thread from the dead, but I've been encountering this problem for the past week as well. Might it really be as simple as a bad batch of gas? I'm not getting the code tripped at anything higher than 2700rpm. It is usually at idle or close to it that I usually get a P0304. I'm curious as to why it is only plaguing cylinder 4.

aguilar45
05-02-2010, 10:27 AM
you running cams? Back from the dead post?

reggieting
05-02-2010, 11:08 AM
if your getting a p0304 try switching it with one of your other plugs and see if it changes to the cylinder you switched to. if it doesn't switch you need plug wires or coils.

Ive been dealing with the p0300 code for 8 months now. Ive replaced the egr hose because i found a hole, I also cleaned the egr valve itself. Ive only had the code set twice since then. And that was it. I drove 1.5 hrs home @ 70-80 and no codes. hopefully it stays like that.

If it doesn't im just going to buy a tactix cable and change the periphery and disable the po3000 code.

biggiesacks
05-02-2010, 11:52 AM
I started getting the code after switching to E85. I changed my plugs and that took care of it.

reggieting
05-02-2010, 11:57 AM
When i changed my plugs RRE told me to gap them at .26 , but it kept throwing the code within 2 miles of freeway driving and i would have to clear the code 2-3 times a day. i recently gaped then at .24-.25 and its been good since.. but like i said if it dosnt go away for good im just going to change the periphery and datalog to make sure everything runs smooth.

EvoVIIIGSR
05-02-2010, 01:40 PM
Alot of good advice and info coming up. My egr hose popped off the nipple a couple times which was throwing a "egr flow insufficiency" code, but I haven't seen it in a while. I replaced the wires about a year and a half ago, and used Ngk bpr7eix plugs for the tune up about 1.5 months ago. Pulled out the #4 plug yesterday and re gapped it to .24/.25....but the code still came back. Running the mods listed below in my sig, and haven't touched the cams yet. I'm generally not getting any noticeable knock at wot, and most triggers for the dtc have been at low and high idle. I'll definitely hit up Rick soon for some datalogging. If the coil over cyl 4 was going bad, would cyl 1 be misfiring as well, or can coil failure be isolated?

reggieting
05-02-2010, 02:59 PM
Try swapping the plugs and see if the misfire changes cylinders. That's where I would start. how long did you drive the car not knowing the egr hose popped off? If it was a while try cleaning the egr valve. There's 3 12mm bolts that hold it.... and if you have access to a vacuum pump i would definitely test it. Ive never really seen too many egr valves go bad.

EvoVIIIGSR
05-02-2010, 03:21 PM
I appreciate the wise words of advice, and i'll definitely try those troubleshooting steps on my day off tomorrow. Speaking of the egr though, could it be that that boost is getting back out through the egr valve and causing that hose/nipple on the bottom side of the intake manifold/throttle body to pop off on occasion?

biggiesacks
05-02-2010, 04:06 PM
the hose that goes to the EGR is part of a vacuum circuit that im sure sees preasure under boost.

reggieting
05-02-2010, 04:20 PM
I appreciate the wise words of advice, and i'll definitely try those troubleshooting steps on my day off tomorrow. Speaking of the egr though, could it be that that boost is getting back out through the egr valve and causing that hose/nipple on the bottom side of the intake manifold/throttle body to pop off on occasion?


The egr hose usually pops off because of increased boost levels, or elasticity over time. Put a little bit of hair spray on the nipple of the egr and it will help it stay on..add a zip tie for insurance.

How much are you boosting?

reggieting
05-02-2010, 04:21 PM
double post sorry.

This could just be one of the reasons to the p0300 code. there are many people who upgraded to sun auto ignition system and have never seen the p0300 code again. its something im looking into if changing my ecu periphery doesnt work.

EvoVIIIGSR
05-02-2010, 04:24 PM
status update: Swapped plugs between cylinders 4 and 3, and swapped coils between 2 and four. This technically rules out spark plug and faulty coil for cyl 4. DTC comes back up with misfire on cyl 4, and its audible in the exhaust...I'm at a loss for what it might be electrically. I still need to check the egr itself, but all vaccum lines appear to still be connected. g2g to work....


as far as boost....( though rick would be able to answer the question better) ~22/23 lbs @boost with taper. thanks again for the help peeps! input is greatly appreciated.

EvoVIIIGSR
05-03-2010, 03:11 PM
Still no luck. Hmm...if I have the code permanently deleted, won't that mean that it won't trigger even when serious misfire due to reason x occurs?

oldevodude
05-08-2010, 04:42 PM
gap new plugs lower and be advised this could be a faulty or dirty injector as well. I had a set of aftermarket injectors and one flowed way different than the others my 300 code moved when I moved injectors is how I knew.

Good Luck