I have a 99' Limited with a 3.4 v-6. About a week ago I replaced the forward oxygen sensor and the coolant temp. sensor. I cleared the codes once the work was complete and the CEL managed to stay off.....until today. I had just gotten about 1 mile from my house and the CEL came on again. I have also noticed that the engine seems to be surging at lower speeds. After the light came on, I ran the scanner again and it gave me the P1133 code, Air-Fuel Sensor Circuit Response Malfunction. I have a Haynes manual, but I can't seem to find out where the sensor is. By the way this 4-runner has about 137K miles on it. On my way home today I stopped by a local mall for a few things and when I went to leave, I was accelerating and the engine was acting like it was going to stall. I made it home ok. Does anyone have any ideas or suggestions?


Thanks!

 

did you ever figure it out? im having the same exact problem

 

Two things it might be. Check your airtube for any leaks like rips or it coming off between the mass air and the throttle body. If all is ok then most likely you have a bad mass air.

James

 

same prob here too
99 3.4L 4runnr 85k miles
mine pulled the codes.....
po172 (Sustem too Rich)(bank 1) and
p1133 (Manufacturer Contrl Fuel Air Metering)
just changed fuel filter with no difference.

Just bought it a week ago, still working out the quirks. Came out of a POS Jeep Wrangler that broke every month. (way too fragile) So I'm being very patient.
nc

 

anyone?

 

Ok, your 2 codes are:

P0172 System too Rich (Bank 1)
P1133 HO2S Insufficient Switching (Sensor 1)

It is likely you have either a bad (or going bad) MAF or a bad front O2 sensor. Since the MAF is the cheapest, I would suggest replacing that first and then reset the codes by disconnecting the negative battery terminal for 5 minutes and then reconnect and drive it until the codes (if any) return. If they do and you still see the same code numbers, then replace the front O2 sensor (there are 2, but just do the front one only). Make sure you only use OEM Denso parts when replacing anything.

Best prices on OEM O2 sensors going:
http://www.urdusa.com/product_info.p...s_id=430006000