Hello all, I'm new to this board and have a problem with my '99 4-runner. It has the 3.4L. It tries to die when coming to a stop and runs really rough. It jerks and doesn't accerate smoothly until the RPM's get over 2000. It also "dieseled" once today for about 3 seconds after I turned off the ignition. And it won't start until you give it gas when the starter turns it over. I went to the car parts store and their computer said (code PO171) that it could be one of several things, including the O2 sensor, the mass airflow sensor(MAF), Ignition misfire, or fuel injection problems. It seems to me that if it was fuel injection, or ignition problems it would do it at all RPMs, so I think it may be the O2 or MAF sensor. They are to expensive to just get both and replace so I'm looking for advice as to what I should try. I'm open to any suggestions, advice, or wisdom. Thanks guys for any light you can shed on the subject. Please help. bell47

 

I forgot to add that the exaust smells alot like sulfer and gasoline. You can smell it pretty strong when you get out.

 

How many miles on it, if over 150k I would replace the O2 sensor if it was mine.

 

I would just do the 02 first due to the money it costs vise the MAF.