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Jack, Auto Service Technician
Category: Car
Satisfied Customers: 531
Experience:  I have been an automotive technician for over 15 years and have worked on most makes and models.
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Toyota 2000 4Runner SR5: I have a 2000 Toyota 4Runner SR5 V6

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I have a 2000 Toyota 4Runner SR5 V6 3.4 L. At low speeds only, approximately 10-20 mph, the engine starts to misfire and starve for gas. After about 5-10 seconds, it starts to clear up and run normally. I have recently replaced an upstream oxygen sensor, mass air flow sensor, gas filter, pcv valve, spark plugs, spark plug wires and had the slow drip fuel injector cleaner s ervice done. One auto shop spent 1.5 days monitoring the fuel pump pressure and various other tests to no avail. They told me they were at their wits end. Another mechanic wants to have me bring it back and do more tests. I have burned out the old fuel and added to new tanks of premium fuel. Formerly, I tried to add dry gas and sea foam and Luekens gas treatment additive. Now, I have another full tank of gas with no additives. It tends to happen more when the engine is cold and after it sits for awhile. When I go very slow and then try to accelerate, it tends to almost stall out and then it finally kicks in. Please give specific advice. Sincerely, XXXXX email: XXX@XXXXXX.XXX

Hello and good morning, my name is XXXXX XXXXX I will try to see if I can help you today, I am sorry to hear you are having such troubles. After reading all of what you have done to this engine my first thought is going to a fuel issue but with all the tests you have done I would take a real good look at the TPS sensor it just seems to be strange that the problem takes place at the same spot. I would first do a TPS voltage sweep test and see if you have a drop out. or has one been done?







Remember, please do not rate until I have earned at least a good to excellent rating. If I can not come to an answer for you I will opt-out and see if another expert can help us out. Thank you.

Customer: replied 4 years ago.

I have just hired an independent mechanic and he was fabulous. He went over the previous actions and then started by looking at the battery and the terminals. To his amazement and mine, the two battery terminals had no nuts secured below them and consequently the terminals could be pulled out easily or even moved atop the terminals installed with the new battery from Sears last year. So, we replaced the terminals with heavy traditional post type terminals. He also cleaned the throttle assembly and butterfly type valve. He also checked for air leaks or brittle vacuum hoses, etc. There is much improvement with an occasional stumble or sputtering at VERY LOW speed and when turning the steering wheel severely to one side. I believe the problem is mostly solved but this occasional sputter still has me concerned. The car is in tip top shape except for this SLOW SPEED PROBLEM. He mentioned that the TPS sensor was not the issue because of how it was running. What else can be checked? XXXXX@XXXXXX.XXX

we can not do email Just answer will not allow that, when you say slow speed how many RPM is it running at idle?
Customer: replied 4 years ago.


When I start the engine it revs up to about 1000 rpms.
It idles down to about 700 rpms after it warms up. It sounds fine at idle. I have been monitoring the tach frequently and it idles at about 750 rpms in neutral and about 600 rpms when I put it in drive. I started the engine after dinner tonight at a restaurant and started to crawl through the parking lot and out onto a busy highway. When I started to accelerate it bogged down again and almost stalled. I waited about 5 seconds and it started to finally accelerate and run fine. It seems to reoccur if I go real slow for several seconds and then try to accelerate. I tried to buy a TPS sensor at a local Advantage Auto parts store and they said that the whole chain of stores was out of that part. Does that suggest that maybe there was a problem with this electronic sensor? My mechanic did not do the sweep of the TPS sensor and said that it couldn't be that part. I am thinking that you have experienced a similar problem and know something about this possible specific TPS sensor that could be causing the problem. The vacuum hoses appear fine and the battery terminals were replaced because they were loose and a cheap type of terminal. The mechanic thought that the loose battery terminals caused the problem as well as a dirty intake valve(butterfly type) and throttle assembly. He also cleaned the throttle assembly area. Still baffled!

I have seen this a couple of times that is why I suggested a TPS scan/sweep just to rule this out it has to be done with a meter and not a scan tool as a scan tool sometimes misses a slight voltage drop you will need to back probe the sensor while hooked up and test voltage all the way through the TPS range just to make positive that it is not dropping out at that point. it just sounds strange that this is happening at the same point every time. a tps sensor kind of works like if you have a series of say 1000 lines and these are contacts then a single contact completes the connection, if say one of the 1000 lines is bad this will cause a drop out does my example make sense. sometimes these can be hard to find. I can not say for certain that this is happening without the test please let me know. thanks Jack
I will be watching for your reply
Customer: replied 4 years ago.

Hi again. I just replaced the TPS sensor. One auto parts store was completely out of them and another auto parts store had only 1 in stock. I felt like this was a big sign about the problem with this TPS part. I ran the car for a few miles and a few trial stop and starts. It sounds better at low speeds and it has not failed yet. Hopefully, you have put your finger right on the problem.... Apparently, 3 local mechanics were not up to speed with this potential problem. I hope that this problem is finally solved thanks to your diagnosis. I will reserve judgement for a few days. I remain cautiously optimistic that the problem is solved. Sincerely, XXXXX XXXXX Jones 2000 Toyota 4Runner SR5 3.4L owner

Ron, thank you for allowing me to help you out. I hope that we have figured this out as well please rate my efforts for you as that is how i am compensated for my time I hope I have earned a excellent rating. please feel free to ask a question about this even after you have rated. please dont rate until I have gotten to a positive rating and keep asking till we solve this. thanks

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Customer: replied 4 years ago.

Sorry to report that the problem has reoccurred after 2 days of running perfectly. It ran smoothly at all speeds and had no bogging or stumbling at low speeds. I exhanged the TPS sensor at the auto parts store and put in another new sensor. I thought that maybe I have a defective new TPS sensor. I drove out of the parking lot where I replaced the 2nd new TPS sensor and the problem occurred after going a short distance. The temperature on the dashboard was normal. The low speed bog happened at about 15mph (1400 rpms). It took about 10 seconds to get through the hesitation of the acceleration. The engine then resumes normal operation at higher speeds(approximately 25+ mph and higher) I need more advice on possible trouble shooting. Thanks, Ron

Ok, sorry to hear that after the tps what I would try is a throttle body de-coking this the cleaning the throttle body of any carbon build up and can cause what is called coking. have you had the throttle body cleaned, I am kind of curious as why the problem went away when the tps was replaced kind of like a wiring issue double check any wire connections, clean the throttle body and retry. you can clean the throttle body by taking throttle plate cleaner and a old tooth brush and cleaning. does this make sense the way I am explaining it to you?

Customer: replied 4 years ago.

Thanks again for your reply. Another retire and I were thinking along the same lines. I will clean(de-coke ?) the throttle valve tomorrow afternoon. We have been checking wires too. Is it possible that one of the wires in the wire assemble to the TPS is shorting or damaged? It seems very odd that the problem was completely solved for a couple days after the first TPS sensor change. My wife just returned with the car and it was very bad for her. It seems that when we leave a parking lot after being parked for 30-60 minutes, the idle loads up with fuel and then it bogs down right away. Is the idle control valve assembly possibly involved in this problem? I see that it is a $200 part and I don't want to chase after it if not necessary. Thanks, I'm hanging in there!

I would do the the cleaning and double check all the wires by the tps sensor and check the grounds as well if you have say a wire rubbing together shorting out this will stop the computer from reacting let me know if there is a lot of carbon build up in the throttle body, I dont recommend that you just keep replacing parts and never get a idea of the problem. I know if gets frustrating but I think you are going to have a wire issue or a carbon issue now that we eliminated the tps let me know what you find