Question about Toyota 4Runner

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Toyota 4 runner 1998, recurring check engine light blinking at high speeds (60mph or above and going by the tach almost always sets the code at 2200 to 2400 rpm or above) and then sometimes stays on or goes out,- using a scanner, it produced codes: po300( random misfire), 302(misfire #2 cyl), and 305(misfire #5 cyl), but no misfire is felt, we have changed plugs, wires and the coil pack that operates spark for both #2 and #5 cyl--any ideas-

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  • 98toyota Oct 06, 2010

    jumping to a $1500.00 computer is pretty hasty for me, especially since there are no tests for a faulty computer---you must have a reason for doing so, --are there no more possible problems that can create this blinking check engine light??

  • 98toyota Oct 06, 2010

    I don't know if you rec'd my reply about, do we have any tests for a bad ecu and how do you conclude that quickly to an item that is $1500.00 from a dealer--is there any other possible answers??

  • 98toyota Oct 06, 2010

    I don't have much to add to the original problem--the 4 runner never had a problem with check engine light on until I started driving above 60mph on the way to Delaware, only takes about 3-4 minutes at high speed (or 2200 to 2400 rpm) the check engine light will also start blinking w/OD off at 2400rpm--any ideas

  • 98toyota Oct 06, 2010

    we actually did try that when we replaced the coil pack, and I thought for sure that the coil pack supplying# 2 and# 5 cylinder would have been the cure, but still looking

  • 98toyota Oct 06, 2010

    well, I went home to get the 4 runner to check the wiring at the coil pack--and the wiring is clipped on tight and I was thinking to check the continuity on the wires but the wire loom looks pretty well sealed and doesn't look like that should be a problem--but it was definitely a good suggestion to check for a loose fit, but after a short ride w/OD off at 2400rpm and yes the check engine light still blinks--any ideas are welcome--

  • 98toyota Oct 06, 2010

    Az--we were actually thinking a possible injector problem as well, so we made an appt for the pressurized injector clean for tomorrow, so I'll keep you post later tomorrow afternoon--checking the wire connection could be tough to get to on the drivers side but we may have to remove the plenum later--

    keep you posted tomorrow

  • 98toyota Oct 07, 2010

    Az--just picked up the 4 runner after the injectors went thru the cleaning process, and yes, the check engine light still blinks when you sustain 2200 -2400rpm for a minute or so--
    ---all ideas welcome--

  • 98toyota Oct 07, 2010

    Az--with the light on , blinking or off, you feel no misfire in the engine--I can run the engine to 5200rpm with the OD/off (light blinking, on or off) and you still won't feel anything, so I don't think it is a bad connection, but rather something in the heating up situation or a wire with too much resistance, or something in that area--I made a call to toyota about reprograming or flashing the PCM, but the tech will have to check tomorrow with someone else because he didn't think that was available for a 98', --all ideas welcome--

  • 98toyota Oct 08, 2010

    AZ--toyota said they have no reprogramming or flashing of a 1998 pcm (just too old)--well, I have to go to Delaware tonite, so wish me luck, hope I'm not walking part way--

  • 98toyota Oct 11, 2010

    Az--let me shed some new light on the blinking light scenario--on this trip instead of trying to sustain one speed for any length of time, I kept varying the speed from 60 mph to 75mph and let it slow back down to 60 and then accelerate up to 75 again, the light (although constantly on for the whole trip), didn't go into the blinking stage for a long part of the trip and when it did start to blink, I accelerated hard (not to the flloor, but hard enough to either downshift or unlock the stall convertor--(1.) putting less load on the engine--(2.) and increasing fuel to the cylinders) and the engine light would blink one or two more times and then stop blinking and return to the constant on and then I would resume the changing speeds until it would start blinking again--so the question is, do you think that by accelerating hard and dumping additional fuel, that caused the oxy sensors before and after the convertor to calm down??--currently, almost any sustained speed will set the light to blinking, not just higher speeds--when I started it cold this morning, the light started blinking??-putting the scanner on it only revealed the same codes, random misfire, #2 and # 5 misfire--any ideas--

  • 98toyota Oct 14, 2010

    Az--I thought about the fuel tank being a problem and still might drop the tank tomorrow, but I have a problem with every time I check the codes, it's always a misfire on #2 and #5 cylinder, so if it were something floating in the tank I would think that at some point it would give me a misfire on a different cylinder--and besides that,I would have to think if fuel was blocked that I would feel some type of loss of power at that point or laying down, which I don't--really seems to be strange problem--
    I welcome any other thoughts or suggestions that I may have time to try tomorrow because I have to run to De tomorrow nite again

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  • Toyota Master
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Hello
It is very possible that this is a software problem, this car uses a system that went into use in 1996 and is the 1st electronic engine control system (known as OBD2) that has the ability to monitor all of the systems that control pollution, misfire monitoring is one such monitored part in the system, software was written to determine when a individual cylinder fell out of the acceptable tolerance of power output and thus triggered a code to be set and the check engine light to come on, many car ,makers including Toyota made the tolerance's to tight and this triggered a misfire code when no real problem exists, to find out if a reprogramme of the PCM (Powertrain Control module) is needed you must contact a Toyota dealer and they can run the symptom on the computer and see if anything shows up, if no need of a reprogramme shows up to fix this issue you do have a problem somewhere in the system whether you fell the misfire or not, the reasons for this can be dirty fuel injectors, engine mechanical wear to rings and valves and a plethora of other issues, only careful testing of the entire engine and systems that control it can determine the actual cause of the misfire. My experience is 30 years as factory trained and certified master tech in electronic engine control theory and operation and repair.

Posted on Oct 07, 2010

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  • yadayada
    yadayada Oct 07, 2010

    add

  • yadayada
    yadayada Oct 07, 2010

    I never said u needed a new computer, the computer in this truck can be re-flashed with up dated programming that may cure the misfire codes, it is the 1st step to find out if a reflash of the EPROM chip is needed, please re read my explanation of the problem, u will find no suggestion that any ONE PART is at at here.

  • yadayada
    yadayada Oct 07, 2010

    correction, "u will find no suggestion that any ONE PART is at fault here".

  • yadayada
    yadayada Oct 07, 2010

    continued

  • yadayada
    yadayada Oct 07, 2010

    U may have a defective fuel injector or an ignition system breakijng down problem, without dealer level testing it is only a guess.

  • yadayada
    yadayada Oct 07, 2010

    how many miles on the engine, has it ever been tuned?

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  • Toyota Master
  • 11,800 Answers

The wiring to that coil pack is loose and when it heats up under heavy use (like highway driving) it starts to lose the contact and generates misfires.
Control very thoroughly all electrical connections and tighten all the clamps.

Posted on Oct 06, 2010

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  • Azrael SRL Oct 06, 2010

    Have you checked the connections to the injectors ? They might be the ones that fail, cutting the fuel flow. Also, since that happens to several cylinders, you should check the status of all the injectors, they might be partially clogged - use a cleaning additive.

  • Azrael SRL Oct 07, 2010

    I'm guessing that - even if the light still pops out - the engine no longer misfires . In that case the only thing left is a bad connection to a sensor - the entire engine harness will have to be checked.

  • Azrael SRL Oct 07, 2010

    Yes, you can reflash the PCM, but i doubt it would help - in this older models it either works or it doesn't, nothing in between.
    Yes, it can be a bad contact that appears only when its heat up the only way to find it is to check all of them with the engine hot.
    The only wires in which the resistance could grow to the point that it could cause a problem are the plugs wires, and you changed those so they can't be it.

  • Azrael SRL Oct 11, 2010

    Blinking signals that a fault occurs at that moment, constant light means that an error has been detected, has passed and has been logged.
    The fact that the error appears while driving normally but it's gone when you floor the engine is quite baffling - it should be the opposite.
    Either you have a bad connection that when the engine is shaken it reconnects by itself or there's something wrong with the fuel delivery system - like there's dirt in the tank that randomly blocks partially the sump or something along the way to the injectors, long enough to cause a misfire in those cylinders.

  • Azrael SRL Oct 14, 2010

    The dirt that floats in the tank doesn't reaches the injectors, its stopped by the filters. But they do cause something else: when it's sucked up it causes a temporary partial block of the fuel, which in turn causes the drop in the fuel pressure. If the injectors on the 2 and 5 cylinders are just a little dirty that pressure drop is enough to make the mixture at those cylinders too lean = misfire.
    BTW if you have just a very temporary misfire you will not even notice it.

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  • Expert
  • 4,070 Answers

Hi! Pretty much a PCM (powertrain control module) problem. The PCM has connectivity on all electrical current that runs inside the car including the engine, transmission, accessories, etc. If the PCM is faulty something will surely fail, one good example is the bad reading on the scanner. Please try to swap PCM and see how it goes. Hope this helps and thank you for using FixYa!

Posted on Oct 06, 2010

  • dj_relly999
    dj_relly999 Oct 06, 2010

    Alright, please try this. Disconnect the positive battery connector and let it sit for atleast 10mins. then reconnect it again. The computer will relearn itself and may resolve it.

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