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95.5-2004 Tacomas & 96-2002 4Runners 4th gen pickups and 3rd gen 4Runners

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Old 07-17-2009, 09:18 PM   #1 (permalink)
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2003 Tacoma occassionally hard to start

I have a 2003 Toyota Tacoma with a 5VZ-FE engine. The truck has 100K miles on it. I am the original owner and all of the maintenance recommended by Toyota has been done at the recommended intervals. The truck has been a reliable vehicle and has always started without problems in 2 or 3 seconds.

I have recently experienced problems with starting. The starter cranks the engine, but the engine does not start. The problem only occurs when the ignition switch has been left in the 'ON' position while the engine is not running for a long time such as 15 minutes or more. After cranking several times, for about 10 to 15 seconds each, the engine will eventually start. Once it starts black smoke comes out of the exhaust pipe and it runs rough for a short while (about 30 seconds).

The black smoke made me think the engine was flooded. I am wondering if one of the fuel injectors is leaking and when the ignition is in the 'ON' position the fuel pump keeps pressure in the fuel lines and any leaking fuel injectors would allow fuel to run into the cylinders.

Does anyone have any ideas about how I would test this theory? For example, I would expect that the pressure in the fuel lines should not drop much after the engine has been turned off and the ignition switch is in the off position. If the pressure does drop that would indicate a leak somewhere. How would I go about measuring the fuel pressure? Would there be an easier method to prove my theory?
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Old 07-17-2009, 10:09 PM   #2 (permalink)
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First of all, did you use the search button?
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Old 07-18-2009, 08:25 AM   #3 (permalink)
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search button nazis
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Old 07-18-2009, 09:00 AM   #4 (permalink)
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http://www.customtacos.com/tech/index.php?article=244

there is a TSP that deals with this issue

and instead of leaving the key in the "ON" position why not use the "ACC position?
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Old 07-18-2009, 04:23 PM   #5 (permalink)
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Thanks to atistang for your suggestion. I reviewed the TSB and found it was for 2004 Tacoma and Tundra. I have a 2003 Tacoma.

The reason for preferring to use the ‘ON’ position is because some accessories don’t function in the ‘ACC’ position.
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Old 07-18-2009, 04:35 PM   #6 (permalink)
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Here is the link for the “INTERMITTENT EXTENDED OR HARD" CRANKING for 2003, 2004 Tacoma:

http://www.customtacos.com/tech/file...anking_tsb.pdf
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Old 07-19-2009, 07:11 PM   #7 (permalink)
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The TSB applies to 2003 & 2004 Tacomas.
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Old 07-20-2009, 06:42 AM   #8 (permalink)
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Quote:
Originally Posted by LifeOnABoard View Post
The TSB applies to 2003 & 2004 Tacomas.
yeah idk where he is getting Tundra at ????
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Old 07-20-2009, 07:40 AM   #9 (permalink)
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I agree with your theory of a possible leaking injector (or two). A fuel pressure leakdown test will only tell you that the pressure is dropping. You would still have to identify the faulty injector.

I would leave the ignition on as you say then attempt to start for only a couple of seconds to confirm that it's in the hard start condition. Then, without starting the engine, pull all the spark plugs to see if you find one or more that are really wet. That should confirm your theory and identify the leaky injector(s).
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Old 07-20-2009, 07:53 AM   #10 (permalink)
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This thread might help http://www.yotatech.com/f2/hard-starting-help-181860/
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Old 07-20-2009, 07:56 AM   #11 (permalink)
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One thing I've noticed sometimes on all of my Yota's is to let the key sit in the On positon for a few seconds, maybe 15-30 or so, before cranking it.
It helps the fuel pump get primed and will usually speed up the start.

That's what I've found at least.

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Old 07-25-2009, 06:43 AM   #12 (permalink)
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I have not done any further investigation on my Tacoma this since my first post, but I have done more investigation on the web and the YotaTech Forum. I appreciate everyone’s input on this. My current thinking is the problem is related to a leaking fuel injector or the other possibility is the TSB that atistang suggested. The specific TSP that he recommended didn’t appear to apply to my Tacoma since I have a 2003, but I was able to locate another TSB that does apply to 2003 Tacomas (see my post on July 18th at 4:23pm). It deals with an electrical grounding problem. I have read many articles on this and found that sometimes applying this TSB works and sometimes it doesn’t. Unfortunately, the TSB requires replacing part of the electrical wiring harness and the replacement wiring harness costs $300. I’m not rushing out to replace $300 worth of parts just to have the same problem.

I appreciate RandyA for the recommendation on a procedure that may help in locating the leaking fuel injector. This seems like a reasonable thing to do. I plan on replacing the spark plugs in September. When I do the spark plug replacement I will first turn the ignition switch to the ‘ON’ position and wait a half hour and then replace the spark plugs.

I see that LifeOnABoard does not think I know about the search button, but I have spent many hours reading the YotaTech Forum and none of the topics that I have read appear to deal with the problem that I am having. That is the reason for starting this thread. I have read previously the thread that you recommended, but thanks for your suggestion anyway.

Overall the problem that I am experiencing with extended cranking has not caused me any trouble in daily use of the vehicle. The primary reason I am spending time on it is because my original thought is that a fuel injector is leaking. If this were the case I expect that as the leak grew progressively worse I would begin to experience other problems with performance and fuel economy.
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Old 07-26-2009, 04:39 AM   #13 (permalink)
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I suggested you do a search and find a similar thread because the same information and findings will just have to be repeated here. I still don't know why you think the TSB above does not refer to the 2003. Yes, it does imply a grounding problem but I've already reported my findings elsewhere and won't repeat myself.

The odds of a leaking injector causing the problem are very very low.
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Old 08-17-2009, 07:50 PM   #14 (permalink)
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Quote:
Originally Posted by jwiemeyer View Post
Here is the link for the “INTERMITTENT EXTENDED OR HARD" CRANKING for 2003, 2004 Tacoma:

http://www.customtacos.com/tech/file...anking_tsb.pdf

For Toyota fix this for free do you have to be under the warranty?
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Old 08-18-2009, 06:07 PM   #15 (permalink)
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lol

2003 -2004 Tacoma

is the same as 03-04 Tacoma

other than that i still don't understand why you think the TSP for an 03-04 Tacoma with the engine you have doesn't apply to your 03 Tacoma
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Old 09-15-2011, 05:53 AM   #16 (permalink)
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So, 3 years later and I finally have an answer to this problem. The answer came unexpectedly and as the result of a repair that I made for what seemed to me to be a completely different problem. The problem was that I began to notice that the engine would not respond when I would press the accelerator. It was a subtle problem and only would happen at highway speeds and only when I would release the accelerator and then depress it again. When I would depress the accelerator the vehicle would not accelerate. Eventually it would accelerate, but it would take some time. The problem was so infrequent I wondered if I was imaging the problem. Eventually the problem got worse such that it would happen at low speeds in a parking lot. I put my OBD II scanner in the truck so that I could monitor the Throttle Position Sensor (TPS) the next time the symptom occurred. As the symptom became more persistent I was eventually able to see that the TPS would not register a change when I would press on the accelerator. Along with the delay in accelerator response and hard starting it seemed to me that the gas mileage had decreased about 10%. I would typically get no less than 20MPG and would often get 21 or 22MPG and occasionally 24MGP. However, it got to a point that even getting 20MPG was not common and I knew my driving habits has not changed that much. Finally, I noticed that the throttle body was making noises that it never has in the past. I had been suspecting the throttle body for a while, but at more than $800 I was reluctant to replace it, but the lack of response to the accelerator finally motivated me to replace the throttle body.

It has been several hundred miles since I replaced the throttle body and I no longer have the lack of response to depressing the accelerator petal. The gas mileage is back up about 10% so that I always get at least 20MPG and often get 21 or 22MPG. In addition, I can now leave the key in the ‘ACC” position for a long time and there is not problem starting the engine afterwards.

In summary, it appears that a failing throttle body caused all of the symptoms. I have the V6 5VZ engine with the throttle body that is controlled with electric motors. I don’t know exactly what in the throttle body failed, but the symptom was that it would not respond to the accelerator pedal being depressed. This could be a failing TPS, but also could be one of the motors that controls the throttle body. I may never know exactly what in the throttle body failed, but since the throttle body cannot be repaired (Toyota provides the throttle body as a unit and none of the individual components on it are available) it does not matter except that it would satisfy my curiosity.
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Old 09-15-2011, 07:19 PM   #17 (permalink)
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^ not clear for me..did you replace the whole throttle body or just the TPS? thanks.

i have been surfing the net and I can't seem to find the solution yet...exactly the same symptoms but very varied solutions.

1. new wire harness
2. TPS or throttle body
3. fuel pump
4. ECT
5. starter brushes
6. fuel filter
7. gas cap
8. injectors
9. sparkplug wires
10. fuel quality
11. fuel pressure regulator
-----
Eleven solutions for almost the same symptoms???
isn't this as complicated as a common cough or just really deceptive?

Last edited by lekiboy; 09-15-2011 at 07:43 PM.
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Old 11-12-2011, 12:43 PM   #18 (permalink)
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I replaced the complete throttle body assembly.
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Old 11-12-2011, 12:46 PM   #19 (permalink)
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Toyota does not make the TPS sensor available for replacement. You must replace the entire throttle body assembly on the 2003 Tacoma.
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Old 11-12-2011, 12:53 PM   #20 (permalink)
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The hard starting symptom the I experienced only occurred when the ignition key was left in the 'on' position for a while. All other times the engine would start easily.
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Old 11-12-2011, 12:53 PM
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