Question about 2001 Toyota 4Runner

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I have a reoccurring problem with a flashing check engine light flashing. the code always indicates an engine misfire. I have replaced all coils, wire set, plugs, O2 sensor and cat. The problem persists. Like clock work, if I exceed 75 mph it starts flashing......diagnosis and other options to look at?

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You need to know if it IS misfiring. Does it shake at idle?
Typically I recommend experienced techs deal with misfires.
the code should say P030x, with the X being the number of the cylinder it believes is misfiring (No, computers arent always right about which cylinder. USUALLY, but not always.)
Lets assume it says CYLINDER 3. (Only your scanner will tell you for sure, 3 is an example we are using for now). You could try disconnecting cylinder 3 ignition coil plug at idle. On a good cylinder that is NOT misfiring, you will hear and feel the engine run rougher and slow down when you unplug its coil or injector. Thats because it WAS contributing until you unplugged it. Your v6 engine idles at say 600rpm warm when its running good. If you unplug any 1 cylinder, youve lost 1/6 of the engine output (actually more due to dead weight drag from that cylinder, but not important for now). SO, if you find the cylinder it says is misfiring, and it loses rpm when unplugged, its probably doing SOMETHING or trying to. If you unplug it and zero change heard or felt, that cylinder is likely dead.

Heres where it gets hard. Could be literally dozens of things that take some familiarity and experience to ID. bad spark, bad fuel mix, bad spark plug, oil fouling, low compression, leaky valves, blown headgasket, leaking intake, EGR leaking at idle, wrong weight of motor oil (some cars) and the list goes on. An experienced drivability tech can usually narrow it down or find it in 1 hour or less. If you are learning as you go, you could take many hours, and still miss things that trained eyes and ears wont.

Start by figuring out which cylinder. If it idles smooth (No shake at idle, and if you clear code and start it and let it idle the light never comes back till you drive over 75 as you stated), then I strongly recommend a professional check it.
If it idles rough and you know which cylinder, you can try taking out that coil and spark plug if you know how, moving them to another cylinder that isnt misfiring, then clear the code and drive it and see if the same code resets or a new code for the other cylinder sets. If the code is the same, you have deeper issues not worth explaining here.
If the code moves to the new cylinder, then 1 or both of the 2 parts you changed are likely at fault. You can replace them an very likely fix the issue.
Again, I strongly recommend professional help. But that may get you started.

Posted on Jan 04, 2018


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Posted on Jan 02, 2017

Big Poppa Ma

Big Poppa Marv

  • 302 Answers

SOURCE: Check engine light on

There are three kinds of gasoline engine misfire scenarios, first there is the "under load" misfire and there is the "at engine idle" misfire, and finally there is misfire continuously. All engine misfires exist because one of three things has occurred. First, a cylinder has lost compression, a cylinder needs a certain amount of compression to operate correctly. Second, the ignition system has failed or is failing intermittently, spark is needed at the time of compression to ignite the fuel air mixture. Third, the fuel air mixture is incorrect, proper mixture is needed for the ignition system to ignite fuel properly. If any of these conditions occur in the engine, the engine will misfire.
1. Low or no compression can be caused by

a. burned or leaking intake or exhaust valves
b. worn or broken piston or piston rings
c. worn out camshaft
d. wrong weight motor oil was installed holding the cam followers from adjusting
e. broken valve spring
f. failed head gasket.
2. Ignition system has failed or is failing
a. spark plug has fouled or is worn out
b. ignition coil
has failed
c. spark plug wires have shorted
e. engine control module coil driver has failed
3. Fuel/Air Mixture is incorrect
a. vacuum leak at the intake manifold
b. fuel injector has failed
c. EGR valve is stuck open
d. mass air flow sensor has failed
e. oxygen sensor has failed
f. air intake boot is cracked

common problems:
1. fuel injector has failed or is failing
2. spark plug wire has shorted
3. spark plug is worn out or is cracked
4. ignition coil has failed is failing

Testing a coil on the car is pretty easy. No special tools are required. Just remember to be careful, the amount of electricity generated by your ignition system can be dangerous. If your coil is already off the car, or if you would like a more specific data-driven test, you can bench test your coil. To set up the test, remove one spark plug wire from its plug, then remove the spark plug using a spark plug socket. Next put the spark plug back into the spark plug wire. Be careful not to let anything drop into the empty spark plug hole -- very bad.

Posted on Dec 07, 2008


  • 12 Answers

SOURCE: Flashing Check Engine Light 99 Camry

light flashes when comp. picks up a skip pull code and it will be po300 random miss p0301 p0302 p0303 p0304 all are for that # cyl that has the miss best bet change wires and plugs check for oil on wire to plug end in spark plug hole leaking valve cover gasket or spark plug tubes...

Posted on Dec 31, 2008


  • 1 Answer

SOURCE: 99 4runner 5vz-fe 3.4 misfire

I know this post is old, but right on the engine theres a sticker that says use multi-ground plugs only. I read a similar problem like yours and it seemed to turn out that the spark was arcing to ground over the ceramic on the plug. So maybe it could have something to do with the single ground plugs.

Posted on Jan 23, 2009

Jonah Oneal

  • 14092 Answers

SOURCE: Code 25 for Toyota 3.0 3VZE


Posted on Jul 20, 2009



  • 23 Answers

SOURCE: check engine light on 2003 toyota tacoma, O2 sensor?

An O2 sensor code is a tricky one. It could mean SEVERAL different things, and I know how bad it sucks to hear this, but your best bet is to take it in and have a diagnostic ran on it at either a dealer or a good mechanic shop with a computer they can hook up to it. I had an "O2" code come up a while back on another car I used to have, and literally spent weeks and hundreds of dollars trying to fix it, and never did. Finally out of desperation took it in, paid the $90, and they found the problem and fixed it in like 30 minutes. Something I would have never even thought of was causing it (can't remember off the top of my head). After that I stopped wating time and money on check engine lights. One comes on in my car, I take it to have it ran for free at and auto parts store just to make sure it's not a loose gas cap or something, just to get an idea of what I'm looking at, then go and make an appointment to have to hooked up to a diagnostic computer to track down the problem. Good luck, and hope this helps save you some time and money.

Posted on Apr 05, 2010

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