I know it should be a vac line I missed, but I've looked six times now can't find it. Checked all plugs in the area of the TB I could have hit. Cleaned and tested MAF and PVC. I know this should be easy to find but..

Any suggestions? I think I may change back to the OEM gasket and run it. I know that shouldn't be it but I need to rule it out...

 

Hey everyone.... after a couple of days of my Runner throwing codes at me, I took the gasket back out and put the original "D" shaped metal gasket back in.

I've driven it several times after that and haven't had any code appear. I'm going to keep the original in for another day or two and then switch back to the TRD "O" Gasket. I will see if I get the codes again after that.

This is hard for me to understand. I haven't heard of anyone else having this problem. Only thing I can think of is this.....

Is it possible that having my K&N kit AND the "O" TB Gasket giving the intake too much O2 and the ECU can't give enough fuel to keep the correct ratio??? I can't imagine it being so, but why else would this happen?

Remember, Code P0171 is System Too Lean, bank 1.

 

Original O2 sensor? I'd give it a week to see if the CEL pops back up, and if it doesn't, leave it alone.

I once swapped out a TB on a Ford along with a new TB gasket and had a high idle problem. After looking for the problem for days, I saw where there was a fine crack in the new TB gasket, which was letting air in. I got another one, problem solved.

 

Yeah, original O2 sensers that I know of. I never changed them since I've owned it. I'll leave it original for several days to a week to make sure I get no codes, but I want to change it back to the TRD gasket just to see if they reappear. If so, I'll put the original back on.

Thanks for responding.

 

Might try flashing your ECU too so it loses its air/fuel "prejudice."

 

I would suggest this. You slightly changing the airflow and might be throwing things off a bit. Try resetting the ECU and see if this does the trick.

Did this mod a few weeks ago with no codes thrown.

 

I've got the higher flow gasket coming in the mail. I'll post my results after I've gotten a chance to install it.

 

I doubt it, some guys run a SC with that setup (remember the "O" gasket was made for and part of the SC kit) and no fuel mods. My guess is one or more of your sensors is failing to give accurate data. I'd start with the MAF since you are using an oiled air filter followed by the front O2 (or A/F) sensor. There could be a fuel pressure problem too, like a clogged fuel filter..etc.

 

I pulled the ECU fuse two different times to clear it. Even left it out for several minutes. It helped with the strange idle, but codes were still appearing after that.

 

Didn't know about the SC "without fuel mods". So you're right, I can rule that out. Just cleaned my MAF and tested resistance on it (didn't test voltage yet). I changed the filter last year so that will be easy to change again. Only thing that scares me is the O2 sensors.... I bet they are original and I would hate to bust \ strip those out.

 

Might need to clean your throttle body, as you may have knocked some crud loose during the installation.

 

No real idea on the cause of your issue but I just added an O gasket on my rig and have had zero problems. The idle was a touch high at first but the ecu seems to be correcting it after a few days.

I notice a bit more response and maybe slightly more pull but it is pretty hard to tell and could all be me hoping for gains. My truck runs good though!

 

It is time to replace the front O2 sensor then. OEM or Denso, no Bosch or other aftermarket. Soaking the mounting nuts with PB Blaster, Kroil, etc. the night before will help in an easy removal.

I would imagine your O2 sensor does not have the ability to calibrate changes correctly or accurately as Dale mentioned given its age. When you changed the air flow with the new gasket, changing what the O2 sensor was used to "seeing", the code was thrown.

 

My TB was really clean. I took a white rag and just with my finger wiped out the inside. Didn't even need any cleaner really.

 

Well, I guess I'll add that to the list of parts to order when I try to get my lift here real soon.

Thanks for all the options and input people.

 

Can someone give me a lesson? Getting different info depending on who I talk to or pages I look up.

Are they both O2 sensors, or is the front an A\F sensor?

From URDUSA:

1999 & 2000 49 State 2WD & 4WD auto V6; Front = 234-4162 1999 & 2000 49 State 2WD & 4WD auto V6; Rear = 234-4162

So are they the same front and rear? Same Part Number... Is it the same device just performing two different functions?

From other threads, it sounded like others have got the wrong O2 sensor. Got a rear one sent to them for the front and it didn't work.

They seem to be cheaper then I though. Several sites I've found for around $75.. (Densos)

 

Most of the threads I've seen about cleaning your TB, guys thought it was clean until they took it off and looked in the bottom. Apparently there's a collection point for garbage down in there that causes some problems. I know when I get my gasket I'm gonna see if I can find what they're talking about. I'll let you know what I discover.

 

try this for the right fit: http://www.densoaftermarket.com/catalog/

For a good price: http://www.amazon.com/Denso-234-4162-Oxygen-Sensor-Ratio/dp/B000C5UFK8/ref=sr_1_1?s=automotive&ie=UTF8&qid=1277913253&sr= 1-1

For me: 234-4162 front and 234-4154, rear, non CA

If your 4 runner was made for CA emissions, it has an A/F sensor. For the other 49 states, not needed. I would think there is a real easy way to check using the VIN rather than crawling underneath. Maybe someone will chime in who has a CA 4 runner. I do not know......

 

Thanks for the info. From that site, it looks like mine are the same front and rear (because I'm auto). I'm guessing you're manual and that's why you have a 4154. Strange why there's a difference between auto and manual. Guess I learn something new everyday.

Thanks again!