hesitation

[konasean]

Has anyone been experiencing what I would describe as a stumble / miss / hesitation / lack of power at 2,000 rpm when under load, going up hill?

It has progressed to a point where it happens all the time now. I constantly need to downshift for higher rpm. Loses alot of power at the 2,000 rpm range.

I changed the plugs and used all kinds of fuel injection cleaners, cleaned the MAF sensor and changed air filter.

Someone mentioned a problem with his torque converter was causing a similar problem. Anyone know?

 

[JP4RNR]

What Year 4 Runner and Engine Size, and displacement

 

[konasean]

Ahh, I guess that would be helpful to know - sorry.
Its a 2004 4Runner 4.7, Sport Editon, Auto. Thanks.

 

[jharris2]

Torque converter shouldn't cause a miss, which you can always tell is coming from the engine. And you've already changed the obvious stuff.

 

[konasean]

Ok, so any ideas? Anyone?

 

[JP4RNR]

Did you check for any malfunction codes?

Maybe you have a bad A/F ratio Sensor (smarter oxygen sensor). Sometimes they can act up and not give any malfunction code. I had hesitation, lack of power, random misfires which was resolved by replacing and A/F ratio sensor that was not giving off any code. The A/F sensors can slow down as they age and not send signals to the ECM in the proper amount of time to provide the proper air fuel mixture and as long as the ECM is receiving the proper voltage from the sensor you may not get a malfunction code

How many miles on your 4 Runner? If you have over 60,000 miles it may be worth it to replace this sensor so long as you have ruled out ignition and fuel system problems, but if you had any significant issues with these symptoms I would imagine you would have seen a check engine light.

Hope this helps

 

[konasean]

I failed to mention that I don't have any fault codes. My mileage now is 57,000. The problem started slowly at around 45,000 and has become worse.

Will a factory dignostic show a bad sensor? Do you know where exactly it's located cause isn't there three 02 sensors on these?

 

[JP4RNR]

I failed to mention that I don't have any fault codes. My mileage now is 57,000. The problem started slowly at around 45,000 and has become worse.

Will a factory dignostic show a bad sensor? Do you know where exactly it's located cause isn't there three 02 sensors on these?

On the old oxygen sensors they could hook up a voltmeter to see how many times the voltage from the sensor would fluctuate in a given time of two minutes at 2500 RPM's. For example if voltage fluctuated more than 10 times in this two minute window at 2500 RPM the sensor was good. If it fluctuated less the sensor was not good. When the fuel mixture goes from rich to lean and back to rich this is noted by the fluctuation in voltage. As I mentioned earlier when 02 and A/F sensors ecm which can upset the air fuel mixture

Toyota dealer should be able to isolate one of the three (I thought there were 4) A/F ratio sensors.

As a test you can disconnect the A/F ratio sensors (you will get a check engine light) to see if this really is your problem. Please note for the duration of the test you will get crappy gas mileage but if your hesitation goes away then you know this was your issue as when you disconnect the sensor the ECM defaults to a rich mixture. If you were losing power your A/F sensors may have been telling the ECM to deliver a lean mixture under load causing the lack of power. If you cause a condition to make the engine run rich sucjh as disconnecting an A/F sensor you may be able to pinpoint the problem. That's how I resolved my issue