Ok, my car has gotten slower recently. There's a noticeable difference from the driver's seat, as it takes much longer to get through the gears on WOT. Also at the track, I've lost as many as 5-9 mph off of my trap times and almost a full second off my quarter mile times. My check engine light is on because of the headers I have. I got the codes pulled, and what came up was the two O2 sensor codes and P0300, which is a cylinder misfire. The cylinder misfire isn't the problem, because this problem just started recently, and I've had that code ever since soon after I put the headers on. Originally, I was thinking it was the MAF, because that seems to be the official maxima.org solution for 90% of all performance problems... but there were no codes for the MAF. So what could the problem be?

 

Is your power valve functioning correctly -- do you notice/hear the change when it closes?

 

whats a power valve? lol

I can feel that it's slow when the car is in gear.. 1st, 2nd, and 3rd are noticeable slower and take waay longer to get to redline under WOT

 

It is the flap/valve in the upper intake manifold that opens/closes to change the flow of air through the IM to provide better lowend torque and better topend power - do you not notice the audible change it's around the 4k rpms mark, you should also feel the dip/change in power as it activates allowing better topend - if you look at a dyno chart you will see this function occuring.

 

oh, is that the flap that's inside the VIAS? if so, then that's off my car right now because i have the NWP block plate on there.. i did not notice any audible change around 4k though.. what does it sound like?

 

Sorry my connection to the forum is very sluggish so was unable to edit my last post. I did want to add that it is vaccuum controlled, you will see the vaccuum leads coming off the left ( passenger ) side of the upper IM -- check all the vaccuum lines as mine was not functioning properly and it was b/c of a leak in one of the lines.

 

Once Again unable to edit my post after seeing your response, sorry!!
Nevermind that, did not know you took the VIAS out. Hmm, is there a way to test out your timing while running the car - do you have any laptop obd2 type software? or any friends w/ OSIRIS? (Titan truck dudes run this and it can read some diagnostic info from your ecu)
You don't have any vaccuum leaks around the IM that may have opened up? How old are the o2 sensors? I'm not quite sure what could cause such a tremendous powerloss, something must be causing a huge drop in timing. Have you tried to reset your ecu at all? Do you have a bad tank of gas? Just throwing out some random suggestions..

 

get some o2 sims to take care of your codes. your ecu is probably running you rich in safe mode to protect your engine.

 

Seriously man just get the O2 simulators and be done with it. Keep your car running right, and it will take care of you and itself.

 

feldman is right, btw happy holidays.. O2 sims FTW

 

but if that were the case, then wouldnt the car have been running poorly right after i put the headers on? i had a good while of nice performance with the headers before this sluggishness started

 

i have a buddy who works at autozone who pulled the codes for me.. i believe he used an OBD2 to scan it

i have no idea how old the O2 sensors are.. the problem actually started when i went to the track and did some runs after putting in some "octane booster" fuel system cleaner from pep boys on about a quarter tank of gas.. i dont remember the name of it, but it was in a red bottle.. you think that could have screwed up something?

 

as a good rule of thumb you should do whatever needs to be done to clear your codes and then take things from there when you are having problems. my guess is you are running rich because of your o2 code which has over time been fouling your plugs which would explain your misfire and the lack of performance.

 

so you think that me running rich this whole time has damaged my plugs, which has hindered my performance? hmm..

 

not sure if its different for the 02 vs 01, but my max didnt throw a code when the maf was bad. i replaced it and my problem went away. have you ruled this out?

 

this is what may have happened but it is always a good idea to take care of problems that you know of before you start chasing others. It could save you a lot of wasted time.


that being said cleaning your maf is a good pice of preventative maintenence which may help your situation...

http://forums.maxima.org/5th-generat...10-w-pics.html

 

I would check my spark plugs and my coil packs......How is your gas mileage?

 

gas mileage is pretty good.. it's gone down a little bit from increased idling times with warming the car up for the winter.. other than that, it's pretty much on point.. i have a 2001 maf from my old car sitting in my basement.. so im gonna try taking that wire from my 2003 MAF, putting on the 2001 MAF and seeing if that makes a difference