Like the title says, I have been having an Issue with throttle hesitation on my 2001 4runner. It just rolled to 79k. The check engine light came on, which also turned on VSC OFF and VS trac lights. When I disconnect the battery to wipe the computer, the light goes away, but when I try to go from a stop, occasionally the truck will hesitate and I will need to pump the gas several times. The pedal can be floored and it won't go at all. Just idle. When doing this, the traction light will come on saying I am sliding, and you will hear the hum in the pedal as it tries to work. After driving for a little while, the lights will come back on and the problem goes away. I have had it scanned when the light is on and it says post cat O2 sensor. Well I've tried two different sensors now and it has done nothing to fix the problem. I had a mechanic check it out who replaced my MAFS and believes it is the cat. His scan gave an error for Cat Efficiency. If that were the case, why would the problem go away when the engine light is on? If it were a blockage issue like he described, it would always be there. Any input is appreciated because I am stumped.
Throttle Hesitation Only When Engine Light is OFF
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Mauzer
New member
Unplug the 02 sensor. It will throw a code, but without input from those sensors, the computer will run a stoichiometric program. If this fixes your issues, then your O2 sensors are the problem If not it may be the cat. I would also clean the TB just to eliminate the easy stuff or see if it affects the issue.
If I unplug the sensor and run it, what should I be looking for?
EatonKyleH
New member
Responded to your PM.
Also wanted to add a P0420 Cat Efficiency code will not cause the symptoms you are experiencing. Although a plugged Cat would (except be all the time not changing when codes reset) and that can be easily tested by a technician with a exhaust back pressure test. I highly doubt that is what is going on but your tech should have been able to give you a proper diagnosis instead of just guessing at trouble codes with out performing procedures/tests to pin point the cause of your complaints.
Honestly though it sounds like you are getting the run around by your tech. I'd recommend seeking a second opinion. Or answer all the silly questions I PMed you but I may be a little hard to follow if I try to guide you through the testing.
Good luck!
Also wanted to add a P0420 Cat Efficiency code will not cause the symptoms you are experiencing. Although a plugged Cat would (except be all the time not changing when codes reset) and that can be easily tested by a technician with a exhaust back pressure test. I highly doubt that is what is going on but your tech should have been able to give you a proper diagnosis instead of just guessing at trouble codes with out performing procedures/tests to pin point the cause of your complaints.
Honestly though it sounds like you are getting the run around by your tech. I'd recommend seeking a second opinion. Or answer all the silly questions I PMed you but I may be a little hard to follow if I try to guide you through the testing.
Good luck!
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First I want to thank you for all your help, second, I was able to follow what you're saying and answered your questions as best I could. Next I would have to agree that my tech is either trying to squeeze me for cash, or genuinely has no idea and is hoping to guess correctly. Either way, I am going seek a second opinion like you suggested. I am not the most mechanically inclined, as all of my knowledge of vehicles is self taught, but I do have a decent understanding of how things work, and logic/reasoning. I was already questioning the mechanics suggestions based on what I do know. Also, if it was a clogged cat, wouldn't I always be experiencing the hesitation? Not only when the check engine light hasn't come on?
EatonKyleH
New member
Exactly. A clogged cat would be a consistent problem and not change when you reset the light. Hence why I doubted your problem has anything to do with a cat.
Just trying to let you know he should have more testing and proof from that testing before charging you to replace parts.
EatonKyleH
New member
Do you have a tool capable of reading basic scan data?
If so:
1. Check calculated load and drive the vehicle about 20 MPH and then floor it wide open throttle and see if calculated load jumps to 85% or more. (it should)
2. Check the MAF Sensor grams/second at idle 3.3-4.7 and 12.9-18.3 at 2500, no load.
You can do that with some code readers... smart phone OBDII apps... or a scangauge.
If you let me know what readings you get doing that I can give you more than a guess.
eric70412
New member
Zero point calibration!!
I am having the same issues with my 2001 as far as the throttle hesitation goes. My engine light is also on but for a different reason than yours (P0770 shift selanoid) I have heard from other forums that people say to get a zero point calibration done for the yaw sensor to correct this problem. Mine has been doing this for about 3 years now and seems to be getting worse slowly, but I just deal with it. Sometimes when I dont feel like dealing with it I will pull the pressure sensor plug on the master cylinder to totally disable the TRAC, VSC, ABS. No more hisitation when this is done.
Check out this link in yota tech that I found several years ago. It tells you how to calibrate your truck yourself and gives you info on this matter. I have not tried this yet with mine & not sure if im going to. Seems like a lot of people fixed their problems by doing this from what I have read on there. Im not sure if im brave enough to try this myself though lol
01-02 4Runner How to Zero Point Calibrate your VSC system. - YotaTech Forums
I am having the same issues with my 2001 as far as the throttle hesitation goes. My engine light is also on but for a different reason than yours (P0770 shift selanoid) I have heard from other forums that people say to get a zero point calibration done for the yaw sensor to correct this problem. Mine has been doing this for about 3 years now and seems to be getting worse slowly, but I just deal with it. Sometimes when I dont feel like dealing with it I will pull the pressure sensor plug on the master cylinder to totally disable the TRAC, VSC, ABS. No more hisitation when this is done.
Check out this link in yota tech that I found several years ago. It tells you how to calibrate your truck yourself and gives you info on this matter. I have not tried this yet with mine & not sure if im going to. Seems like a lot of people fixed their problems by doing this from what I have read on there. Im not sure if im brave enough to try this myself though lol
01-02 4Runner How to Zero Point Calibrate your VSC system. - YotaTech Forums
