ok guys....here's my CR@PPY dyno from last weekend.

What I find the most wierd about it is that my peak torque is at 3300rpms.....nowhere near where is should be...

ignore the first pull....it was done with the hood down and no fans on the car at all.....

 

2 things can cause this a knock sensor and/or a bad ECU. I'm leaning more toward the KS because a bad ECU would put you in fail safe mode. My advice is to get the car datalogged with a scan tool and find another maxima to have the samething done. This way you can see if your ignition timing is way off what the other person's car is. From the looks of the dyno I'd say the ECU was pulling your ignition timing heavily. Try disconnecting the KS and see if the car drives the same.

 

I already REPLACED the knock sensor 2 days before the dyno....

 

Anybody have any other ideas about this?

 

The first dyno looks correct, I say it was a bad dyno run, not the car.

 

The first dyno is worse than the second one! Besides there were 3 other maximas dynoing that day on the same dyno within an hour of each other. Both of the other 4th gen 5-speeds put down 180+ hp with the same and LESS mods than me. My car is also MUCH slower on the street than the others.

 

Here let me analyze it for you... your car sucks!!! Haha

 

Hmm if the KS has been replaced, there has to be a restriction somewhere. Does the car idle fine or is it slightly rough. Here is another question does your cooling fans always stay on? There are a couple thing that I can think of that would affect the engine power. They are the KS sensor, engine temp sensor, MAF, CAS and maybe a malfunctioning EGR valve. I'm not sure if you have done a compression test either, if you have can you repost the results. You are losing power somewhere. Either way you will need to datalog it, nissan's CONSULT would do the trick but it would probably cost you 1-2 labor hours at the dealer. A scan tool and display sensor info also, so it may help.

 

did a compression test a while back when the problem first started....and I was between 205 and 210 psi in every cylinder.

 

you replaced the cat if i remember correct. umm have you tried just resting the ECU and looking for codes are random, maybe a bad O2 sensor and you are running rich, robbing power?? jsut a thought.

 

I have checked the ECU for codes, and got nothing. The O2 sensors wouldn't affect my dyno at all because the WOT fuel map is a hard program on the ECU, therefore once you go WOT the O2's readings are bypassed. Hell, just look al Nealoc187's dyno....that was done with 2 bad O2 sensors....one of them with a cut wire! Thanks for trying though

 

you've tried everything, i've been following your slow car saga. i can't think of anything else other then the mobiltek rc fuel injector service www.mobiletek.net

 

Have you solved the problem yet? If not, why not get back to the basics, like clean your air filter and MAF. Maybe you under-oiled your K&N. I cleaned my K&N once without oiling it, just vacuuming off all the dirt and putting it back on. I figured on not oiling it because it was only in use 5000 miles. Well, my car felt awful after a while, like it was starving for air. So I took it out and re-oiled.

As for the MAFs, use electriconic parts cleaner,stuff that does not leave residue, not carb cleaner or anything else like that. I got this tip from Matt93SE. He has quite a bit of experience cleaning MAFs.

DW

 

He said he over-oiled his K&N.

He just dropped $400 on a new MAF and he installed it last night... He didn't say whether it solved his problem though. Brian???

 

That's not correct...well sorta but not entirely.

Although you are correct that in WOT, the ECU totally bases the fuel settings based on the MAF readings, the ECU also uses values from a correction table to adjust those WOT values. The correction values are obtained while the car is running in closed loop mode...in other words, when the car runs in closed loop mode, if the feedback from the O2 sensors tells the ECU to adjust the fuel flow beyond a certain threshold for a sustained period of time, the ECU will adjust factors in the WOT correction table. In other other words, if the ECU makes sustained adjusments in closed loop mode, it will try to correct the WOT maps, assuming that a similar adjustment will be required in open loop mode.

So, if the O2 sensors are bad (ones in the ypipe...not the one downstream of the main cat...that one's just making sure the main cat is working), you WILL get messed up WOT/open-loop fuel flow.

I would replace both ypipe O2 sensors.

BTW it does look like your problem is tuning. If you are seeing knock retard, it could be due to a lean condition. A rich condition would obviously also result in a power loss.

 

One more thing to check is your MAF sensor. Oil buildup on the hot wire probe or the inlet screen. A bad MAF will also hose your power.

 

if that is true about the 02s than please explain to my why Nealoc187 put down MORE power than any other 4th gen with just intake and y-pipe...and has run 14.45 with JUST a y-pipe. Both of these things were done with a CUT rear bank O2 sensor (we cut it becase it was already throwing a code before we installed his y-pipe, and the 02 "hex" was partly stripped, making it almost impossible to remove with an open ended wrench)

I'm not trying to flame here....I just don't think that my 02 sensors that aren't throwing any codes...could possibly be at fault.

 

how about a clogged cat? or maybe the exhaust has a clog in it some where.

 

Maybe it's the ECU. Didn't Nissan change to a more sophisticated ECU for the 97-99 Maxima?? Like go from a 16 bit computer to a 32 bit one? Maybe the older ECU was more forgiving of an O2 dis-connect. That would make sense given the te GForce chip only works on 95-96 maximas. They haven't been able to 'fool' the newer ECUs

DW

 

you have nitrous right? Do you have colder plugs installed in your car ? Colder plugs will affect the power when you are off nitrous...but I am sure you already thought of this. Borrow someone's ecu and give it a shot, just in case yours has gone bad.

 

that was going to be my next guess swap - out ecus with someone.

 

Nismo2020 - I already swapped out the cat for an R/T unit.

ECU is my last resort....when I got dyno my car next month I'm going to do one pull with my current ECU....see how the numbers are, and then do another pull with BEJAY1's ECU......

I pulled my intake manifold yesterday to replace a sticking injector...and the cylinder 6 runner had LOTS and LOTS of sludge in it....kind of wierd...cylinder 1 runner was almost perfectly clean...and all the other runners were kinda in the middle...just a little dirty...

 

Looks like you're onto something. Does finding that sludge suggest that NOS had messed up the PCV system in your car?

DW

 

how would NOS mess up a PCV system??

BTW...I replaced my PCV valve a few monthes ago...

 

I don't know how, but I thought that the PCV system is supposed to prevent sludge accumulating insdie the intake manifold.

DW