Code 300 - random misfire

abrad

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#1
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MAKE:Toyota
MODEL:Corolla
YEAR:2000
MILES:132,000
ENGINE:
DESCRIBE ISSUE....Been having an issue with this code for the past year or so. The first thing I did was replace the spark plugs, figured it can't hurt, they hadn't been replaced in awhile... Still get the code, but nothing specific that seems to cause it (i.e. - wet weather, temps below zero, etc). I just recently replaced all 4 coil packs, but the code came back. I tossed in some seafoam last week, and all was good. Until today!

Next up is to start chasing the individual wires backwards looking for wear or rub spots, or possibly a tiny little crack. I've also noticed comments about possibly a low fuel pressure could cause this, or low compression.

Car has plenty of get up and go, although the wife describes it as "sluggish" at start up - sometimes. It usually starts right up whenever I go out and start it, so not sure what she means. Of course, I get the "look" like I'm supposed to instantly know exactly what she means!

Anyone else run into similar situations, or have any ideas what else to look for? I'm off Sunday, so guess what I'm going to be doing...
 

nickb2

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#2
A po300 (random misfire) can be tricky to pin point.

I would sure start by getting some comp readings to rule that right out of the way.

So, 4 new coil pack, spark plugs, Idea, have you noticed any oil in the spark plug tubes? You may have an oil leak stemming from the valve cover grommetts that have deteriorated the spark plug boots. That is a very common p0300 issue on these engines.
 

abrad

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#3
Hi Nick. No, I have not seen any oil leaks. When I changed the coil packs last month, everything was dry...

I'm fairly certain I'm going to be pulling my hair on this one!
 
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#4
There are no other codes?
You are focusing on ignition-
have you checked fuel pressure?
Vacuum leaks?
A scanner showing DATA would give a quick snapshot - ECT, FT's, MAP/MAF, even the o2 voltages will give clues.
 

abrad

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#5
That's the only code, the other things are what I plan to start looking at this weekend, actually Sunday, when I have a day off!
 

nickb2

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#6
What did you use to pull the code?

Also, if you are in the habit of driving with low fuel, that also could account for random misfires, especially if everything checks out ok.

As Kev pointed out, vacuum leaks and fuel pressure could account for that also. A bad coolant sensor also. It may only be missing during warm up. So try to get vac readings and temp reading right at start up on a cold engine and make sure tank is at least 1/4.

Although a vac leak is usually accompanied by a lean code, I would still monitor fuel trims. Anything +/- 10% is suspect. AT 20%, I would be amazed it hasn't coded rich or lean codes.

Also, measure resistance of each injector, which is easy to do on these engines. Should be about 13.8 ohms at 68deg f. Fuel pressure should 44-50psi. Cleaning the MAF sensor also may help. A proper cleaning of the injectors and combustion chambers also will help.

If and when all this is checked out as to be ok, spark fuel, and air, then start suspecting valve clearance or valve timing. I am assuming you will do the compression check before we get to valve clearance and valve timing.

When doing the injector pressure cleaning, also clean the throttle plate (both sides of plate is preferable) , throttle body and IAC. I am also assuming the air filter and fuel filter are new, yes?
 

nickb2

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#7
Car has plenty of get up and go, although the wife describes it as "sluggish" at start up - sometimes
That comment of your wife is telling you something that confirms what I wrote above, so checking this engine cold is a must due to that comment. That is probably where the random misfire event is stemming from. After a nights rest, right in the morning is best so the engine has had a full cold night soak. I don't know what temps you are getting down in new york, but they should resemble what we are getting here close to montreal.
 

abrad

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#8
Sorry it has taken me so long to get back to you. Life interrupts the best of plans. Still having the same issue, although it did go away for about a month after I cleaned the MAF. Air filter is relatively new. My biggest problem is having the car here when I'm home! The boy has soccer practice, the daughters have this event and that to go to, and I'm working 60 hours a week not counting going to and from work!

As for what I'm using to pull the code, I have an Autel. I'm hoping to get a free weekend soon to chase down your other suggestions, especially the cold start and vac leak...

Spent this past weekend evicting a LARGE nest of yellow jackets from the bedroom wall in the boys room. Stud to stud, and about 2 feet top to bottom. Had to tear off the outside wall to clean out the nest, and of course then I had to rebuild what was torn out! No rest for me!!!
 

nickb2

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#9
Spent this past weekend evicting a LARGE nest of yellow jackets from the bedroom wall in the boys room. Stud to stud, and about 2 feet top to bottom. Had to tear off the outside wall to clean out the nest, and of course then I had to rebuild what was torn out! No rest for me!!!

Well that sucks large. Not good for the bank account unless you just won the lotto 6/49, For me, that would be burnout beach. Especially since I am allergic to bees. I need an epipen thingy like my father.

As for Autel, great company, I work with a maxisys all day long. Love it.

So since it took so long to respond, car is still going into drive, I figure you good for soccer practice. MAF cleaning seems to have helped, I think I covered the rest, this engine just needs a very through cleaning of the intake system.

Have a god day, you will need that to restore life back to normal after that hornet thing.
 

nickb2

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#10
My english sucks, is a yellow jacket a hornet?

I think it is. I think I need a wikipedia correction here before I say anything else stupid.

I got stung two months ago my a bumble bee. The dart on that thing swelled my hand to the size of a pamplomouse which I think in english means grapefruit.
 

abrad

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#11
Yellow jackets and hornets are not the same. Equally nasty...

Car is definitely drivable, just that stinking check engine light coming on! NY inspection is good till next year, so I have time to keep playing with it...!
 

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kev2

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#12
After playing novice be keeper - That is in dad job description.
.
any luck getting . data- ECT, MAP, FT's etc and have you looked a freeze frame ?
 

abrad

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#13
Wow! Just realized I never posted back on here to this thread! Couple cans of seafoam, and the wife has been keeping the gas tank above 1/4, and the check engine light has been off now for several months! It even passed the NYS inspection earlier this month with flying colors!!! Probably just jinxed myself...!
 

abrad

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#15
I am surprised as well...! Last time I cleared the codes was in January, and haven't had to do it anymore. An earlier post had suggested that keeping the tank a bit over 1/4 might help, which I thought to be ironic as the wife likes to drive till it hits E, then wants her 6'4" husband to take her midget clown car over and gas it up for her because it's after dark and she doesn't feel safe going to a gas station after dark. I instead got in the habit of just dumping a 5 gallon can of gas in, rather than trying to squeeze my frame into that little car! Once it warms up, and the snow stops (just saw an article predicting another potential nor'easter coming our way (would be the 4th in three weeks), I plan on looking into a few more possibilities. Right now I'm so done with winter! Alternator s$&! The bed on my van Monday night, didn't get a tow until 1am. Spent Tuesday getting that replaced, then had an issue with interior lights, electric door locks, radio, blower, and rear wiper not working. Turned out to be two separate blown fuses. When that thing went, it must have surged before dieing. Internet search brought up lots of people had similar issues.