96 t100 misfiring, out of ideas,, help - Toyota Nation Forum : Toyota Car and Truck Forums
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#1 Old 09-22-2008, 05:41 PM
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96 t100 misfiring, out of ideas,, help

96 4.3l v6 t100 missing on acceleration. I replaced the spark plugs and it seemed to run much better for about 5000miles then I changed coil packs and plug wires, and it ran better for a while. Then I put in orig equipment plugs in and thought I had it fixed. it ran great for about 5000miles again, now it is doing the same thing. When I pull the plugs out they look good. light tan in appearance. The truck seems to run fine until it warms up, maybe even until it gets hot. any suggestions. Oh I did replace the o2 sensors and changed the mass air flow sensor. I checked the tps using a scan tool and it appears to be working fine. It is not setting any codes. any ideas out there.
Thanks,
Todd
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#2 Old 09-22-2008, 08:28 PM
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You need to find out if it is only one particular cylinder is misfiring or all of them are. This can be done if you have the proper scan tool, or you can drive it until an engine misfire code sets. If it is indeed misfiring, even if it cannot narrow down to one particular cylinder, it should still set a P0300, random misfire code. BTW, have you check for pending codes in the system.

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Last edited by new echo owner; 09-23-2008 at 07:25 AM.
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#3 Old 09-23-2008, 05:17 AM
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There are no pending codes set. I assume it is a missfire. I feel it bucking on acceleration. I am not sure how to determine which cylinder since it does not do it all the time.
Thanks,
Todd
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#4 Old 09-23-2008, 07:26 AM
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If it is engine misfire, it would have set a code, pending or current. Was there something else done to the car besides replacing those parts you had mentioned.

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#5 Old 09-23-2008, 03:16 PM
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no, nothing else has been done. The Truck ran pretty good today. on the way to work I did not notice any problem. on the way home it ran great until several miles from home. I drive about 30 miles each way. Could a fuel injector be causing a hesitation like this. that was my next idea, but I still do not know which cylinder.
Thanks,
Todd
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#6 Old 09-23-2008, 03:33 PM
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That is highly probable; bad fuel, sticky injectors, but still it would have set a code, either pending or current. How frequent does the problem occur?

What you need is real time data, that monitors the input to the ECM. The dealership scan tool has this capability as well as the higher dollar scan tools out in the market. It will allow you to look at the fuel system input and also misfiring input to the ECM.

In the mean time, if you haven't before, run some fuel system cleaner through the system and see if that help.

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#7 Old 09-24-2008, 05:17 AM
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I have run over the counter fuel injector cleaner through the tank with no noticable difference. I have a scan tool that can read live data ( like a autoxray except a cheaper version, different brand) and it shows no codes set. I tried to look at the different readings on the fuel trim and could not tell any difference when it was running poor and when it was running well. It runs with what appears to be a miss every day now, usually worse when it is hot outside and when the engine gets hot. The last two times when I changed spark plugs the problem seems to dissappear for several thousand miles. when I look at the plugs they look great.?????
thanks,
Todd
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#8 Old 09-24-2008, 08:47 AM
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Can your scan tool monitor real time engine misfire data?

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#9 Old 09-24-2008, 11:04 AM
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no, it looks at o2 sensor data fuel trim values tps values intake temp, but nothing on firing or engine miss. it is basically to reset codes.
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#10 Old 09-24-2008, 11:27 AM
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If that is the case, you might want to think about taking it to the dealer when it is acting up and have them connect it to their scan tool. That way you will be able to get a definitive answer on whether the engine is misfiring or not, or what cylinder is misfiring if it is.

After you have obtain that information, you can then decide whether you want to tackle the task or let them make the repair.

It is not always fun having to deal with the dealers, however, when they are the ones who have the means, you just have to bend a little.

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#11 Old 03-20-2009, 10:12 PM
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Engine misfires on my 1006 t100 3.4 4x4 AT

It started with slight misfires. So I changed fuel filter, air filter and plugs. Ran fine for a week or so. Then it got worse. Misfire and stalling. It would start up again, but was not reliable at all. Went to AutoZone and got codes pulled. It is a free service. It showed multiple cylinder misfires, and a bad ignitor. Took it to the dealer, put in a new ignitor, and new plug wires. Most of the issue went away. Now just have an occasional hesitation or slight misfire. The last code that came up is an ECU (Engine Computor) issue. It seems to be very intermitant. The ECU is 1400, went to www.auto-parts.com it's a website by salvagers. Found one here in CO for 135 and am putting it in tomorrow. Will let you know if that is the issue. The dealer even talked to the Toyota Engineers and they think that after not finding the issue in all the testing that there may be a bad transistor or diode in the ECU????
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#12 Old 03-21-2009, 01:58 AM
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Quote:
Originally Posted by kylebasa View Post
It started with slight misfires. So I changed fuel filter, air filter and plugs. Ran fine for a week or so. Then it got worse. Misfire and stalling. It would start up again, but was not reliable at all. Went to AutoZone and got codes pulled. It is a free service. It showed multiple cylinder misfires, and a bad ignitor. Took it to the dealer, put in a new ignitor, and new plug wires. Most of the issue went away. Now just have an occasional hesitation or slight misfire. The last code that came up is an ECU (Engine Computor) issue. It seems to be very intermitant. The ECU is 1400, went to www.auto-parts.com it's a website by salvagers. Found one here in CO for 135 and am putting it in tomorrow. Will let you know if that is the issue. The dealer even talked to the Toyota Engineers and they think that after not finding the issue in all the testing that there may be a bad transistor or diode in the ECU????
Did you ever clean out the throttle body and the IAC (Idle Air Control) valve? Make sure you git the gasket as it will swell if you git the cleaner on it.
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#13 Old 03-21-2009, 06:21 PM
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Stutering t100

Thanks but went there after the fuel and air filter. It was supposed to be back from Toyota today, and service hasn't called back. Imagine that.
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#14 Old 03-27-2009, 11:27 PM
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Well, so you know I have a similar problem on a 97. I have changed the plugs, wires, coil pack (for cylinder 3), all of the boots, and the Throttle Position Sensor. It also runs well for a while and only starts to "act up" after warming up. I am getting a mis-fire check engine code that says that cylinder 3 is mis-firing. I have changed all of the parts for cylinder 3 but the problem continues. I haven't changed the fuel filter yet, but may shortly. I am too almost out of ideas.
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#15 Old 03-27-2009, 11:30 PM
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What kind of plugs did you put in?

Have you cleaned the throttle body and IAC? How about the MAF?
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