Help me out guys, my 2000 SE hesitates when I try to speed up. When I gradually speed up, I have no problems but when I am around 45mph and try to floor it, it feels like it loses power, the rpms will hit between 4000 and 5000 and the engine revs up like it is trying to accelerate but it kicks in slowly. I took it and had it hooked up b/c recently my service engine light came on and the computer said I had a bad o2 sensor. Could this be the cause of my problem?

there is a technical service bulliten on the 02 sensor which requires an o2 and a reprogram. but your loss of power problem is not because of that. you have a bad mass air flow meter. if the final 5 digits of your meters part number is ad200 there is an updated part for that which will also require a reprogram of the ecm to the most current revision part number. be aware if you take it to the dealership they will miss diagnose this problem because it seams there is a fail safe in the computer most of nissan north america corp's technical staff does not know about. when the problem occurs the airflow voltages registered in consults data moniter will read correctly. this reading is NOT right it is a sustituded value by the cars ecm. if when driving the vehicle with consult in data moniter the techcian should select mass a/f(volts reading not grams per sec) a/f alpha b1 and b2 , o2 sensors b1 and b2 (fronts) and inj pulse b1 and b2. when hard accelerating the readings will look as follows(or close to it).

mass a/f 3.89va/f alpha b1 113a/f alpha b2 113ho2s1 b1 0.00vho2s1 b2 0.00vinj pulse b1 7.0 msecinj pulse b2 7.0 msec

This car will drive like it is hanging up in gear and not shifting and can be miss diag and have a the shift solonoid bulliten performed. when looking at the data moniter readings it is clear the ecm is not adding the proper fuel to meet the airflow meters request. under hard accel the injectors should peak between 11 and 12 msec with an airflow meter reading like that. the o2's and air fuel alpha both indicate the the car is infact running lean. therefore it is obvious the airflow meter reading is mearly a substituted value. this condition can at times throw a lean fuel code but in most cases i have dealt with this is not the case.

Thanks! Do you think that a certified nissan repair shop can do it instead of the dealership? They obviously want to put a new tranny in for $3000 and that was the only option that they gave me. I asked about the mass a/f sensor and they told me that was not the problem even after I told them that I had the same problem with my I30t. Is this considered the same thing?

GOOD GOD!!! I hope shops across the contry arent pullin this sh**. go to a dealer man print the post i gave you and have one of the master techs look at the consult readings and look at my post. do not go to the nissan certified shop I doubt they have the technoligy to perform the reprogram I mentioned. Let me tell you what i do for a job and a story about how this problem was discovered. After I figured this out Every one i have repaired since has been what I call a gravy job. I have repaired myself and other guys on my team I have desigated this exact problem approximatly 40 times due to this problem. to be quite frank i dont understand why nissan has not addressed this with a TSB.

I am an engine specialist for a nissan dealership in calif. I am currently the crew leader for 5 technicians.

This problem first presented itself to me about 6 months ago. customer came in concerned his car would hang in gear and did not seem to have the horse power it use to. I road with him and sure enough above half throttle this car was a gutless wonder and it would hold at 6000 rpm before it would up shift into the next gear. so I go back to the dealership and told the customer on the way back I was familer with his problem and that there was a TSB on replacing the shift solonoid kit and that would need to be done. well one of my guys performed that job over the weekend and on monday when i came back to work the car was still there and I was told the car was still acting up. Well dog poop I thought. It acted exactly like other ones I had done the bulliten too? Except one thing the horse power problem was not a charicteristic of the others. So I check our Asist (nissan information data base) for any other possible no code related horsepower problems. Nada! So off to the phones I go to call nissan technical help desk for dealers only. well we went back and forth 3 or 4 days and none of their recommended advice helped me in resolving this problem. He ran it by the engineers down there and they also came up with nothing usefull for me. So now I am pretty much on my own here. I went to the data moniter section and seen what was on the screen. Drove it 6 or 7 times watching this stuff which made absolutly no sense what it was showing me. I evaluted all my print outs and took a shot at a ecm reprogram only just to see what would happen. well it certainly made a difference. After the reprogram and clearing self learned values my Air flow meter readings plummited and all the other readings fell in line with what air flow was doing. its voltage erratically jumped around 2.5 volts at full throttle. BANG I got a bad airflow meter and for some damn reason the ECM leaned this and sustituted its value in data moniter. Well at this point the car runs like absolute crap bogging and sputtering when accelerating. So I get the new Airflow meter (updated part number) and reprogram the ecm for the new part number and the car runs ti*s now.

Now the failure seems to have variable degrees of failure. some not so bad and some to the point of good luck gettin on the freeway. and injector msec will folow this variance but o2 readings will still follow the reading i indicated. Also I have done curiosity reasearch on the reprogram and cars drivabilty dropping off like that one did. some of them will not change on how they drive because it seems to be dependant on how bad the airflow meter actually is. And when I called techline back to tell them what i had found they swore to me there was no failsafe mode like i was seein. So it wouldnt suprise me if other dealers have not figured this out. That is why you should take my diagnostic steps i included with you. If they are good techs they will understand all the info I gave you and be able to make the repair. DO NOT let them sucker you into the trans replacement. the airflow meter is running like 120 bucks, thats cheap for an airflow

Awesome, I will try this in the morning. Hopefully this can reconcile my problem. Thanks man!

This is a great thread and derserves extra exposure.I will copy it to our Nissan Online Mechanic section.

Fred..

PS: :bowdown@Nistech