Bad Dyno - car isn't running well
 

I sent this to Moncef, as he has been very helpful in the past. However, I figured I would toss it out there to the wealth of knowledgeable folks on here as well.

I have an Altima 3.5SE 5SPD--POWER MODS:
AEM CAI
Stock exhaust, mufflers removed (tips only)
Racingline high flow pre-cats
Stillen Y-pipe
Ralco RZ Pulley
SSIM


PAST INFO:
I purchased some high-flow precats from RacingLine and they've been running fine--verified at the track.

I had an Exedy clutch and Fidanza flywheel put in, because my clutch was slipping at the track.

I also purchased an AFC Neo w/ Boomslang cable and recently installed it AFTER my problems occurred.

CURRENT SITUATION:
So the day after having the clutch installed, I was driving and got a P0171 code--lean on bank 1. My gas mileage dropped from around 22-23 to 16MPG, so to me it seemed the car was trying to compensate for this lean code by dumping tons of fuel.

Among, the o2 sensor and a vacuum leak fix, replacing the MAF was also listed as a viable solution for this P0171 code. I had an extra 2001 w/o the IAT wire (P0114 code thrown) so I installed that and my mileage went back up to what it was before, so I was content for a while.

At any rate, just to ensure things were going fine. I decided to visit a shop and run a dyno yesterday and here are the results: Red is my last run from March(I/E/Y/SSIM only), Blue is the run from yesterday (I/E/Y/SSIM/P/HFPCs)

http://i781.photobucket.com/albums/y...11-23-2010.jpg

Too rich--do you know what could be wrong? Bad o2 sensor (P0171 code)? Would the missing IAT wire cause that crazy erratic behavior in upper RPMs?

I'm done throwing parts at the car until I can get this resolved.

so no more vacuum leak?

i had a problem like this and it turned out my cat was clogged later down the road i found out however and it cost me an engine

While trying to figure out what was wrong a mechanic looked over it and didn't find any leaks. I guess I worded that funny. I was just saying what the possible causes of the P0171 code could be.

I think leathe hit some good points on nissanclub, I am sure someone has some good info here....... good luck.

id lean toward the maf if its p0171

Thanks. Gene provided some good info. I became a little too content after my gas mileage went back to normal.

+1.

This is Gene btw. :D

Well, I guess the question still stands then, would having no IAT wire actually cause that erratic behavior on the dyno and cause me to lose so much power up top? Quite a few people here have swapped out a crappy MAF for one from a 2001 Maxima.

It could account for ****ty fuel economy that's for sure..as your afr would be effected..as far as power, it is possible. as a bad iat sensor could also have the same symptoms as a restricted cat - less power in that case

when they swap out for an 01 maf, it requires a little modification
http://forums.maxima.org/5th-generat...-pictures.html

Yes I know about the IAT sensor, I know about the code, know about transferring the wire over with the thermistor. Nothing new here, I've read that thread. No one verified any difference on a dyno with or without the IAT sensor though. Just to let you know, the fuel economy is BETTER with the 2k1 :) Prior to swapping out for the 2k1 I was getting 16MPG with my other 02 MAF, down from 22MPG. Now with the 2k1 I am getting 24MPG (verified at the pump).

Did you go over my last PM?

Yeah I sure did, thanks Moncef. I'll hit up the shop tomorrow and have them test the o2 sensor. Is bank 1 up front, or is that the rear one :( I'll make the change of 4 in 4 out on the Neo.

with 50 posts i wasnt sure :laugh:

Yeah, I spend more time posting on Nissanclub and more time READING on Maxima.org :D But I am using a 2k1 MAF because I know it works. Going to go get the o2 sensor tested today, hopefully it fixes the problem.

Bad O2 sensors arent going to cause a loss of power under WOT. At WOT, the ECM runs in open loop and uses MAF voltage and a predetermined fuel table to control injector pulse width. I'm not saying your O2 sensors are fine, they could very well need replacing but its not going to solve your power issue.
Can you borrow a MAF from someone and throw it on? According to the A/F log, you're running very rich past 4.5k rpm.

I did get the o2 sensor tested today and it was lazy. The MAF during the dyno was not my normal one, it was an extra 2k1 that I had and swapped due to the original giving me bad gas mileage. The 2k1 improved my gas mileage, but the P0171 (lean code) also came back (bad o2 sensor). Right now, I have the original MAF back in there--I'll get a new o2 sensor and go back to the dyno when I get a chance and run it again.

That 229 is nice #'s but that to 192 is whoa hope you figured what the problem was to get that power back!!:D