I suspect it is the MAF or the MAF connection via the VAFC-II. The torque is dipping and spiking everywhere over the power band.

Additionally, when compared to others' dynos:

1. The torque and power curves are way below theirs. And I mean WAY below.

2. I take 5-6 seconds LONGER to reach redline than healthy 5.5 Gens with headers.

All constructive feedback is appreciated, esp from those of you who are experienced in diagnosing problems from dynos.

http://forums.maxima.org/showthread.php?t=466569

 

Do a motor swap and drop a 3.0 de-k in and you'll be all set

 

I have a 2k max with headers,injen intake,underdrive pulley and i got it dynoed 4x,on all of them my hp was low.Like around 170,but my tq was 190.It was like that for years no error codes.Then i changed the maf and it all changed.I have not dynoed it yet but i can feel a different. I would guess its the maf

 

I guess start with the little things...

What gas were you running?

Last plug change?

Still on original coils?

Exhaust leaks?

Dents in headers (hit anything)?

Drive by wire working correctly?

 

Your best thing now would be some type of sensor monitoring device.


harrison r&d software from obdscan.net

 

1. Shell 93 Octane

2. Never changed em, 50k miles

3. Never changed em, 50k miles

4. Last I checked there were no leaks.

5. Not that I know of.

6. Closed and WOT throttle voltages are in spec, that's all I know. What else should I do to check that?

 

When I had a power problem (surging in and out delayed motor reaction) it was my coils, they were just starting to go and they f*ed the car up.

PS- that was at about 50k miles.

I took it to Nissan and they hooked it up to the Consult I think and it printed a graph of the actual surging in the coils. Where the graph should have been a smooth curve it was spiking and diving all over the place.

 

The impression that I got was that the power problem with bad coils was much more severe, but then again, that is probably subjective. My torque curve definitely shows surges in power. I may have to give Dave B a call this week. Thanks for the info.

 

I think it depends on how many are bad and how "bad" they are. I think they get worse over time and I cought mine early.

 

In your case, it may also be your VIAS. Do things level and fall off after 5k rpms? If so, look for Irish44J's thread in the Dyno forum because that's exactly what happened to him.

 

Yeah, true. Good point.

I'm gonna go through things one by one later this week:

Vacuum lines
MAF (gonna try to clean it )
Exhaust leaks
Intake leaks (might try a new filter too for the heck of it)
All VAFC-II connections

Then if I still can't find anything that changes things:

Seafoam (to check for leaks I may not have found)
Coils
Plugs

 

What was it like before the VAFC-II?

 

I thought it ran better before the VAFC-II was installed, but it may have been already going bad then. Sort of a coincidental timing thing. The MAF/MAF signal is still my primary suspect.

 

Why do we even have MAFs?!

 

Um yeah... they are kinda important...

 

Found some time to check the intake and vac lines... no leaks found yet....

Time to clean the filter and MAF...

 

Can you describe briefly the procedure you did to install the VAFC II so I can do it and see if I get the same results. Do you just connect it to the ECM and just follow some instructions posted by SR20DEN??
Thanks,
Jesse

 

i know my car is weak, and i'm not sure why. No codes, no starting problems or anything but every time i face another max i have troubles. My friends 00 auto completely stock like me keeps up wit me on the highway and it has codes out the a$$. Another guy in an 01 5 speed with ONLY a catback (2.5" with no resonator) walked me all over the highway the other day like i was racing an M3 or something. I'm not into heavy racing like i used to but plan to be some day...i hope your prob is solved puppet but rest assured u r not alone

 

Joel....I have thursday and friday off (need to burn some vacation leave), and will be doing a few things on my car. If you want, we can work on yours as well. I have my stock MAF (not blown, to my knowledge, but probably needs cleaning) in the trunk of the car (emergency MAF!) = not sure if it will work on the 3.5, but we can try.

We can also try the "coil resistance test" with all 6 of your coils if you want....see if any of them "appears" bad - worked for me when I had one go bad.

See if you can find any of that CNC MAF cleaner locally - the advance auto near me doesn't have it, but maybe Fairfax Auto Parts....

I'll give you a shout out on Thursday, see what you're up to.

 

since you have a spare maf just switch the IAT sensor from the 5.5 gen and put it on the 5th gen maf and try that out.

 

You can come over and use the garage.... just bring your race jack and grinder too.

 

MAF should work even without the IAT sensor...just swap it over quickly instead of opening up your MAF and transferring that IAT over...only thing is, your gonna throw a CEL for IAT...but thats about it...should run exactly the same

 

Yes, if the MAF is good, it'll run fine w/o the IAT. I knew that, but thanks anyway.

 

my vote is coils.... back in 2001 I dyno'd with a y-pipe, UDP, RT cat, and intake and my numbers were like 20hp, 15tq less than normal and the graph was spiky as hell.

Swapped coils and dyno'd again like 30k miles later and all was normal.

 

Find anything out?

 

Did the accelerator pedal and throttle position learning/reset procedures, as suggested to me by Juice, but it didn't help much.

Getting an 01 MAF tomorrow to test.

 

Good for you.

now open your messenger

 

Man if you guys didnt live in VA I would be down there in a flash... Basically you arent worth 500 miles on my car

Speaking of which... I'm starting to wonder why my slightly low original dyno had something to do with coils/maf. Once hopefully I wont have the same troubles when I tune.

 

Thanks... I think coils will be a last resort for me, but I suspect that you're right.

 

Who said we wanted you down here?

 

Update:

Swapped in another .Orger's 2001 MAF w/ IAT and it didn't change things. We're pretty certain it isn't the coils. OBD-II scanner picked up no codes. All sensor voltages on the VAFC-II are in spec.

Next move will be to disconnect the AFC and reconnect the MAF wire to see if the AFC unit or AFC connections are the problem.

 

can't wait for the results...goodluck

btw, they (nissan) raised the price on coilpacks...I bought mine last year around this time...and got them @ a dave B - ish price of $300 shipped...now they are soaring up to $400 shipped even @ daveb's price

 

I'm secretly hoping that my AFC is broke so I can get a EU....

 

damn, EU? would you be the first 2002 max to have it?

 

do not forget that most dynos are at the wheels, so when you dyno it, it would be a lot less than spec because it is your whp, not hp at the crank

 

 

 

Did you even look at the graph? It is spiking and diving all over the place.

just get the EU anyway. Im hoping in may or june to pick one up

 

I did not forget.