need some help.

Supra725

Supra725

New member
Yesterday, I finally got around to changing the o2 sensors.. and it went well.

But, now I'm having acceleration problem.

Whenever, the car would accelerate really slow like is lean or something..

the car is like coughing or hesitating.

So far, i had change the oil, spark plugs and wires, fuel filter..

What is it that's causing it to behave like this?

could it be a bad fuel pump? or something else?

thanks
 
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I would clear the ECU first, maybe it's too much of a difference for your cars current configuration.

Try that and if it doesn't work, I am not sure.
 
Will Do.

I put some new fuel in her too last night..

Maybe it will take the ecu a little bit of time to compensate for the new oxygen sensors.

the car did ran rich for the last 2 and a half weeks..
 
I had a 98 that had a similar problem except that it got so bad it would backfire sometimes. It turned out to be the MAF. I would try cleaning the throttle body first.
 
I had that early on. It threw a system too rich CEL code at the same time. Cleaning the throttle body was the cure. It was as though someone had painted the inside with yellow varnish. I then learned to run a bottle of Techron through the fuel tank before every oil change. The problem never happened again, and when I clean my TB it barely needs it.
 
Durk,

did you remove the whole throttle body to clean it or just sprayed it and cleaned it?

was this after replacing the o2 sensors? cause mine threw po125,po1130,po1133 and po1135 for the last 2 and a half weeks.

This is the first time that it ever happened to me.. the car felt like it was refuse to go..

Was this the tutorial you used?

Toyota 4Runner Highlander Throttle Body cleaning and O Gasket Mod

or did you use another tutorial?

I try looking into the Haynes but no dice..

thanks
 
Are you sure you got the right sensors? When mine went bad I found it sort of confusing trying to choose O2s because mine's an Oklahoma truck (first 4 years) but I live in CA and the sensors are different. I had to look at the tag on the bottom side of my hood to find out I have a non-CA in CA.

I could be totally off here, but don't the later models like '99+ have A/F meters in the front instead of an O2 (I think I remember reading that somewhere along the way)? I don't know??
 
Well,

I just got off the phone with my mechanic and looks like we have ordered the wrong sensor.

the front sensor number is

Engine: V6 (3.4L)
ID: 5VZFE

234-4162
Images Exc. Calif.; Auto Trans; Exc. Calif.; DENSO is the O.E. Manufacturer / Oxygen Sensor

That's the current one I have in my runner..

I should have order this one..

Engine: V6 (3.4L)
ID: 5VZFE

234-9002
Images Calif.; 4WD; Auto Trans; Calif.; DENSO is the O.E. Manufacturer / Air Fuel Ratio Sensor

The back one is this..

Engine: V6 (3.4L)
ID: 5VZFE

234-4153
Images Calif.; 4WD; Auto Trans; Calif.; DENSO is the O.E. Manufacturer / Oxygen Sensor

Now this makes a lot more sense why my car was hesitating and all. slow acceleration and throttle response..

my question is now though, whats the difference between the cali spec and the federal spec one?
 
Supra725 said:
my question is now though, whats the difference between the cali spec and the federal spec one?
Click to expand...

The Cali./2001+Federal wide spectrum Air/Fuel sensor in the front is a totally different animal from the classic O2 sensor used in the 49-state/Federal pre-2001 one-cat system.. Now going beyond my technical depth, but the O2's simply vary resistance according to the oxygen concentration in the exhaust gas stream. The A/F sensor apparently operates at a constant voltage (4.8V DC I think) maintained by the ECU, and the ECU measures the variation in current through the sensor at that voltage. Uber-geeks please feel free to correct or clarify--but that's how I remember it. Also, the different location means a longer/shorter wire and I thought the plugs were different to avoid this happening. Did your 49-state plug right up??

Always go here (URDUSA) to get the correct Denso number. I have never seen a better list, or even one as good.
 
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Looks like we have the wrong sensor for the front.

When I took it in to my mechanic, we had to shave some of the plastic off in order to make it work.
 
Supra725 said:
Looks like we have the wrong sensor for the front.

When I took it in to my mechanic, we had to shave some of the plastic off in order to make it work.
Click to expand...

Yeah, that plastic was added(or slot/corner was removed from the harness) to keep O2 sensors out of A/F holes.
 
I'm going to go switch it out tomorrow.

This explains everything. The car hesitation, laggy throttle response.

My other question,

the cali 99 4runner does have Air Fuel sensor than o2 sensors for the front correct?

thanks.
 
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Supra725 said:
I'm going to go switch it out tomorrow.

This explains everything. The car hesitation, laggy throttle response.

My other question,

the cali 99 4runner does have Air Fuel sensor than o2 sensors for the front correct?

thanks.
Click to expand...

Yes. All two-cat systems use the A/F which is '99 and '00 Cali.s plus all 2001+(50-state).
 
Thank Dirk,

going to the shop in the mornings and having it change..

my mechanic did told me to try a few things though.

I disconnected the negative cable from the battery and the car doesn't seem to hesitate anymore..

would you recommend cleaning the maf and the throttle body also? or should I just leave it..

thanks.

Bryan,

by the way, thank you..

you brought up an very well idea.. If I didn't go back and look at the part number.. I would still probably be stumbling tonight..
 
Supra725 said:
Thank Dirk,

going to the shop in the mornings and having it change..

my mechanic did told me to try a few things though.

I disconnected the negative cable from the battery and the car doesn't seem to hesitate anymore..

would you recommend cleaning the maf and the throttle body also? or should I just leave it..

thanks.
Click to expand...

Usually, when you disconnect the battery, people complain that the car runs poorly as the ECU relearns the correct fuel trim. Who knows what will happen with that sensor in there??

As to the MAF/TB, when were they last done? If you don't know, do them. I do them every 15k. Both are still pretty clean when I do them.
 
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I'm going to bump this thread because I ran across an article I had bookmarked about the difference between the wide-spectrum A/F sensors and normal O2 sensors. The question has been asked more than once and this is the complete answer. Feel free to file under 'More than I wanted to know'.

Wide Range Air/Fuel (WRAF) Sensors

A/F's are used in the front in Cali. '99's and '00's and all 3Gen (50-state) from 2001 up.
 
Durk and Brian,

Thank you..

next time when I'm going to Socal, let me grab you a brew

Dirk, can I ship you a 6 pack?

I took in to my mechanic today and had it swapped out.. also had the Throttle Body clean..

She runs a lot better and no hesitation as of tonight...

I need to clean the throttle body some more this weekend and probably the maf too..

on a side note, I'm thinking about pressure washing the engine.. Thinking about using Simple Green for the degreaser.

Is been a while since I had washed the bay. Is there any spots I should avoid before cleaning it?

thanks..
 
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It's so nice when they run sweet again. I love the sound of that V6. Happy to help.

On the wash, I rarely have to do it. There are electrics all over that bay and I try to just stick to cast engine metal and places with no wires and little boxes. I can get a lot of crud off with just compressed air.
 
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