Ding Ding!

 

I am confused. I was actually agreeing with you, the truck could run fine without a rear o2 sensor, it'd just throw a CEL. His front was worn which he replaced and his rear is probably still fine.

 

No dude! I know we're on the same side here with regards to pulling the rear and life would be fine - BUT!

He replaced the REAR and says it's running better. That was the point of my "plea" to you - I'm looking for someone to bounce ideas off of as to how this could be.

 

Allow me.....it falls into my "slim chance to none" category.

"OBDII cars have two oxygen sensors to measure the amount of oxygen contained in the exhaust gas. The first or primary O2 sensor is located on the manifold or header and measures O2 content of the exhaust as it escapes from the cylinders. This sensor is used by the ECU to calculate fuel trims and look for combustion problems.

The secondary oxygen sensor is located after the catalytic converter and is used only to detect the performance of the converter. The ECU does NOT use any data from the secondary O2 sensor for engine management. The ECU will set an CEL (check engine light) for code P0420 if the catalytic converter is removed, the sensor is removed, or the sensor goes bad. "

This is also why you can use a secondary O2 sensor emulator like Gadget sells to bypass the system when using it in offroad conditions.

 

I must be losing it Well I think im going to definately put the old one back in the rear and move the new one up front.

Moral of the thread...you may want to replace these at some point if you have over 100k..it could make you think youre getting better performance

 

That is exatly what I would do in your case.
Hopefully you'll see an even bigger improvement this time.

 

Ahh I see, sorry. Well, in this case I think it's just thinking it made something better, I guess.

To prove my theory, I am gonna tell you about this dream I had the other day where (no kidding, this dream actually happened) I drove off a steep decline and got my truck high centered before I went down (and basically scraped my whole underside). When I got out to see the damage, the frame was disconnected, the exhaust was messed up and the rear o2 was ripped off. Then, I found myself in my garage all of a sudden leaving the frame behind and driving off in my "body only" 4Runner whose engine ran like crap and could only go less than 15mph.

I wonder if this thread had any influence on my dream, because I could swear I thought of the thread in my dream when I discovered the o2 sensor.

Weird... :pat: :pat: :pat:

 

__ __

 

Here is my experience...

I was coming back to AZ from WI (was about 20 mi. from the house) when the CEL came on and I was thinking, "oh crap...road trip broke the truck". Once the CEL came on, I was getting 13.4 to 14.5 MPG at best in the city (yes, I am one of those people that calulates stuff like that on every tank). This was when the truck was at about 92K miles.

A trip to AutoZone told me that it was the forward O2 sensor (P0171 and one other). I ordered the URD O2 sensor for the truck and installed it in about 10 minutes. I reset the ECU and filled the tank that night. That next week driving to and from work in Phoenix traffic I brought MPG up to 18.7. From then on...18.4 average per-tank. I can really screw my mileage up if I jump on it quite a bit. I have strected it to as far as 19 city taking it easy.

So your results sound very similar to the results that I posted here last year.

One other notable...I could see my mileage drop with every tank of gas on the way back from WI so I can only imagine what was happening to the O2 sensor over the course of that day.

 

Ahh I see, sorry. Well, in this case I think it's just thinking it made something better, I guess.

To prove my theory, I am gonna tell you about this dream I had the other day where (no kidding, this dream actually happened) I drove off a steep decline and got my truck high centered before I went down (and basically scraped my whole underside). When I got out to see the damage, the frame was disconnected, the exhaust was messed up and the rear o2 was ripped off. Then, I found myself in my garage all of a sudden leaving the frame behind and driving off in my "body only" 4Runner whose engine ran like crap and could only go less than 15mph.

I wonder if this thread had any influence on my dream, because I could swear I thought of the thread in my dream when I discovered the o2 sensor.

Weird...

Toyota, Meteor proof!,Lol.

 

hey all i need a bump on this thread!! I have had an awful three months trying to get my cel straightend out. it all started on a rainy night i was changing my air filter in my garage and i guess some rain dripped around the engine and messed something up. as soon as i started my truck it had a terrible idle, it just rumbled and sputtered then the cel came on. so i went to autozone they checked the code and told me i had a missfire on bank 1. so i bought all new plugs and wires and installed them perfectly. drove the truck down the road and everything seemed perfect, even a little more peppy than before. next day i go to work and the truck is rumbling and sputtering again and cel comes on(but only when idleing). so i go back to autozone, this time the code says my o2 sensor is bad. so i buy the bosch one they had in stock and installed it. again truck seemed to run good that night. Next day on the way home from work it starts rumbling and cel on again every time i stop at a traffic light. this time im tired of autozone so i take it in to toyota. they inspect it and tell me my mass air flow sensor is bad. so i buy a toyota maf and install it. truck ran good again, but a few days later same crap. and thats where im at now. SOMEONE PLEASE HELP ME. IM ABOUT TO BLOW THIS TRUCK UP IF I DONT GET THIS STAIGHTEND OUT!!!!. ps sorry for the long post

 

Okay... The engine getting wet with a bit of rain shouldn't hurt anything. Think about blasting through a puddle or running through the mud. Shouldn't be an issue.

So, a recap...
"One day you started your truck and it idled horribly". You end up swapping plugs, wires, O2 sensor and a MAF. _wow_

First a suggestion... Given the $$$ you've spent, get an OBD II reader. It'll save you some headaches and diag charges from the dealer. You don't need anything exotic, just something that can show the code and let you reset the lamp. Figure $40 online, $60 at AutoZone.

Then, questions...

• Did you gap the plugs? What to?
• Which O2 sensor did you switch out? (you have two of them) btw, Bosch ain't a good choice here.
• "cel comes on(but only when idleing)" - does this mean that it goes out on it's own when you're under power?
• Have you reset the ECU or just cleared the codes?
• Cleaned the TB, air filter, TPS?
• Replaced the fuel filter?
• It looks like you've done the ISR mod, are all the caps/inserts still there? *CHECK* to be sure

 

[*]Which O2 sensor did you switch out? (you have two of them) btw, Bosch ain't a good choice here.
i swapped out the one up front on my header that was the one suposidly pulling the code[*]"cel comes on(but only when idleing)" - does this mean that it goes out on it's own when you're under power?
no once it comes on it doesnt go off(i pull the negative cable every now and then to see if it will stay off or not[*]Have you reset the ECU or just cleared the codes?
i have tried both[*]Cleaned the TB, air filter, TPS?
i cleaned the tb after trying to replace the o2 sensor diddnt work[*]Replaced the fuel filter?
its only about six months old[*]It looks like you've done the ISR mod, are all the caps/inserts still there? *CHECK* to be sure
not positve what your talking about (caps/inserts)

 

Your sig says that you did the silencer removal, so did you pull all the silencer boxes and replace them with "plumbing end caps"? If one of those got loose, you'd have very similar symptoms to what you're looking at. It happened to me once...

Also check all your vacuum hoses... remember that there are a couple kinda' hidden under/behind the throttle body.

I'm thinking that you either have a vacuum leak or are getting "unmetered air" into the system (air into the intake that didn't come through the MAF).