1994 OBD1 FZJ80 idle problem/02 sensor over and over. (1 Viewer)

Joined
Jul 30, 2008
Messages
47
Guys, this has been going in for 2 years. I have a 94 OBd1 Fzj80. I’ll put in new NTK or Denso sensors and all will be good for a while. Then after like three months my idle will start to go chug chug chug when I start her up in yhe
Morning. Then while driving I’ll feel the car running rough and it will throw a check engine light saying an 02 sensor will be the culprit. What keeps causing this? Bad cat? These are factory original cats. How do I diagnose and really pinpoint cause?
 
Joined
Nov 9, 2012
Messages
10,847
Location
Olathe, KS, USA
Guys, this has been going in for 2 years. I have a 94 OBd1 Fzj80. I’ll put in new NTK or Denso sensors and all will be good for a while. Then after like three months my idle will start to go chug chug chug when I start her up in yhe
Morning. Then while driving I’ll feel the car running rough and it will throw a check engine light saying an 02 sensor will be the culprit. What keeps causing this? Bad cat? These are factory original cats. How do I diagnose and really pinpoint cause?
Consider temp sensors, injectors, vacuum leaks, and poor O2 plug connections.

All of these will give bad O2 readings.

Any of these bad or poor can give erroneous readings and can throw codes or cause rough operation.
 
Joined
Jul 30, 2008
Messages
47
Consider temp sensors, injectors, vacuum leaks, and poor O2 plug connections.

All of these will give bad O2 readings.

Any of these bad or poor can give erroneous readings and can throw codes or cause rough operation.
Do you mean coolant temperature sensor?
 
Joined
Aug 3, 2020
Messages
26
Location
California
I had a very similar rough idling problem and replaced the coolant temperature sensor. It's been a couple of weeks and I have not seen this problem so far. I first replaced with a non-Toyota sensor (~$10) and the engine kept stalling just once in the morning right after the first start up. The engine runs fine without the rough idling after a re-start with this cheap sensor installed. I then replaced the cheap sensor with a Toyota sensor and I was able to get rid of both rough idling and stalling. I still get the error code 25 for a short time (CEL comes on and goes off) occasionally. I think it is caused by a fuel injector.
 

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