Hello All,

I'm not new to the forum and definitely not new to Nissan's, but I have come across a weird problem that has been plaguing me for a couple of weeks. I have read countless threads on members whips with similar problems, but mine might have an extra twist or two. My car is a 2002 Nissan Maxima SE Auto. It is very well kept and well maintained for the most part, but I have an issue with the car whereas it is extremely down on power and under load, it has no power past 4000rpm, but it will rev very slowly past 4000rpm.

Things I've already done:
1. Rebuilt engine in 2012
2. Changed all cats during rebuild in 2012
3. Changed fuel pump and filter in 2012
4. Changed coils in 2012
5. Changed spark plugs numerous times as recent as 6/15/2015
6. Changed all cats 6/13/2015
7. Changed fuel pump, filter, regulator and dampeners 6/14/2015
8. Changed AFM with NEW OEM 2001 Max unit and thermistor 6/12/2015
9. Changed all sensors before (Aftermarket units)
10. Changed ECU because it was burned. No cam phasing on bank 2 (fixed)
11. Changed all timing chains and keepers 4/5/2015 (Bad upper keeper)
12. Changed all seals 4/5/2015 (No leaks)
13. Changed transmission 4/7/2015


Could it be the accelerator switch/sensor? The VIAS is functioning just fine. I am still using the stock AFM because it didn't seem to be too fond of the NEW AFM from the 2001 MAX, though it did drive nearly the same. Can rev past 4000rpm with no load, but hesitation around the 4000rpm range. So for now, let's rule out the AFM and get into the technical stuff. Just some more background on my ability, I build and tune nissan engines mainly the CA18DET engine. This VQ35DE is a bit on the sensitive side and I would like the help of my Nissan brethren who have more knowledge of this engine than I do because it sure as heck is no CA series engine. BTW, I rebuilt it myself and the rebuild has over 140K miles since rebuilt in June of 2012. Again, let's try to avoid the AFM or MAF for now, though that seems to be the common cure for the cars. Fire away guys and any help would be greatly appreciated.

Dee A.K.A boost_boy

 

Anyone? Don't be bashful about chiming in. I know the "ALL" cure for issues with these engines are the "AFM" or "MAF" , but after reading countless threads, I took the advice and changed it to the recommended unit and the car's performance is still the same. Again, the car drives nicely under 3800rpm and light throttle (30%), but when or if you exceed the that threshold of throttle input, the engine's rpm just hangs at or around 4000rpm and will eventually climb slowly. If this is the AFM or MAF, then the new one did the same thing and I've swapped back and forth a few times already. When I exceed 30% throttle input, the timing goes down to around 5-9*. I ordered a new Knock sensor, but I highly doubt that will solve it, though I'd like to be wrong. For those that chose to chime in, please read thoroughly to see what has been done already.

 

if your maf was faulty, you wouldn't make it over 2500rpm

 

do you have full rpm range in first gear? or is it like that in all gears?

 

It can actually rev pretty good in first gear, but it gets caught-up a bit at or around the 3800-4000 rpm range and then continue on rather slower than normal. It cranks right up and drives pretty good until it warms up and then its sluggishness in the upper rpm area starts. As I stated before, it has no guts past 4000rpm. I changed to a used knock sensor and the car does a little better than with the previous knock sensor. I ruled-out the AFM/MAF because I put the new one and it actually performed worst than with the original one. Coils are good, spark plugs are good, harness is grounded, new ecu, very clean engine with no leaks, cam phasers are functioning as intended, but at W.O.T, the timing goes down to 11-12* now that I've changed to the junkyard knock sensor.

 

Need to get that timing back to where it would be @ WOT, which is lower 20's or so, even at worst. Try the resistor mod and see if that does anything or get a new KS. Couldn't hurt. Just make sure to torque it down to factory spec since that particular item could have a alrge impact of torqued too tightly or too loosely.

 

Here's an excellent look at where the basics of my engine's performance is at during W.O.T . I hope that today is the day I receive the new knock sensor arrives, so that I can take an honest assessment of where this engine/car is at emotionally. And god forbid somethign is wrong with the new ecu (I highly doubt it), my time is running out to get an exchange. This car has lost it's dayumm mind, I tell you.

 

Update:

I have changed my average (185 psi Per Cylinder) VQ35DE for a 2008 Maxima VQ35DE with just over 74,000 miles on it and the engine still lacks power in the upper rpm range (what a waste of time). Even added new injectors during the swap-over as my old injectors were pretty old. I have even detached the exhaust system (post-cat) in an attempt to eliminate possibilities and to no avail. Fuel trims are somewhat normal except for the FTLT b1 which is either slow at times or stays the same @ or around -6.3. No codes, but worse...no power= No fun. I know the Maxima is not suppose to outperform my 500+CA18DET powered
S13 Coupe or my similarly powered CA18DET impregnated B12 sentra, but man this car is lazy as hell on the top end. Could it be in the throttle body circuitry? It is the only thing I haven't changed yet. Your hypothesis will not be disregarded

Dee A.k.A boost_boy

 

Final Update: Problem Fixed

Did a hard reset on the ecu using the ignition switch and pedal method and the engine is now revving with authority and power again. Unfortunately, the transmission is having issues from 1st to 2nd gear now. This is definitely a female car in the fact that it needs so much attention, very costly and is only good for the moment...J/K. Time to get a low mileage transmission that doesn't slip and I don't know that won't be that easy, but at least I have power. Thanks to the few that attempted to offer their hypothesis, but it is time to lock this puppy up, moderators.

Thanks

 

Is there a link or a how to, to reset the ecu?

 

This is not an accurate statement from my experiences. I own a 2001 Maxima SE and my car was experiencing very similar engine malfunction characteristics. I could get up to about 4200 rpm's before my engine lost all power, but below that it seemed to have ok power. Turns out that my VIAS mechanism was broke internally (JB weld the rod and plate back together) AND I had to buy a decent quality ($75?) AFM sensor: Just the sensor not the housing. Fixing the VIAS was not enough by it's self in my case. The OEM AFM
on my 01 SE made it to 200k Personally I'm impressed.