Looking for some help tracking down some issues I’m having with my 2003 Maxima equipped with the VQ35DE engine and 4 speed automatic transmission. Recently the car is not making the same amount of power it use to from what I believe is the computer restricting me. This problem started after I put bad gas (87 octane from a local gas station) in the car and took it to track. The car ran great for the heat race and fell on its face during the feature. The car had very poor acceleration and felt doggy down low. I drained the fuel when I got home but ending up snapping the nipple on the fuel assembly doing so. Went to a local salvage yard and purchased a pump/assembly from an earlier maxima with the vq30de engine. Not the same assembly but I made it work. I then put 93 octane in the tank and took it to race night again. Same issue car was slow and not accelerating quickly at all and now had a hesitation when you fully matted the pedal. I cleaned the MAF sensor with some crc maf cleaner and noticed a decent change in acceleration and no longer had the hesitation issue but now has these random bursts of power that last all of 2 seconds then quickly go away and the car goes back to its mediocre speed that gets passed by grand ams. This random burst of power that comes and goes instantly leads me to believe the car is being restricted by the computer for some reason.

I would also like to add that I had cut off the exhaust including the cat in the mix of all this happening. I have had the suspicion that the o2 sensors may be causing this issue but have read elsewhere that the maximas at full throttle go off of maf readings for how much fuel is delivered to the engine not the o2 sensors. This may be wrong I have no idea.

So what’s my next move, throw a bunch of money in o2 sensors and a maf sensor? I’d rather not to be honest as it was an auction car that I got for dirt cheap just to race at the local track. With that said though I hate losing to other oem v6 cars that should be much slower than my maxima.

 

Might've finished off the knock sensor. Stick a 560K resistor into the harness connector and see if the power returns. Pedal dance reset for funsies to make sure old tables are cleared.

The bursty symptom is pretty suspicious, though. I'd swap the maf, regardless.

And holy ****. even with auto that thing must rip given the um...weight reductions.

 

Assume you have no codes. Is your VAIS working properly? At idle have somebody rev the engine a little past 3K and watch to see if it moves.

 

I was just thinking the same thing about the knock sensor and as to why the car might not of advanced the timing once it detected the better fuel. I also did order an eBay maf today for $30 rather than pay autozone $180. Just hoping it doesnt have to be programmed from the dealer.

And yes the car felt completely different once I gutted everything and took it for a drive. You can feel how light and nimble it is and WAS much quicker. Just wish my dumbass wouldn't of put 87 in it..

 

vais? and no codes light up on the dash but when i plug my obd scanner it has one code for cruise control and even when cleared comes right back.

 

Well anytime you accelerate what your doing is pressing a pedal that opens the throttle plate. As you press, the throttle plate opens allowing more air in to create more pressure and combustion
so if your pressing the pedal and not getting the response you expected sounds like you may need to make a few adjustments.

as far as the fuel pump the 02-03 has the fuel pressure dampener connected to the pump assmbly. I guess you just bypassed that? In the 01 its attached to the rail.

 

The secondary o2 sensors aren't used for tuning. They're just there to monitor the pre-cats.

I'm surprised you don't have any codes.

The 3.5 cars do have a different pump. Not sure it it's just a fit issue or if there's something else. On the 3.5 the fuel pressure is regulated by the computer so the pressure at the pump is constant. No external pressure regulator in the line.

I really don't think the cheap gas broke the car. The knock sensor will detect the cheap gas and detune accordingly. You'll lose power but shouldn't break anything.

 

 

What about the motor mounts. Especially the passenger side one? I read repeatedly on here how bad motor mounts impacts the performance. Binds up the drivetrain. Have you replaced all that? Sorry if I missed it in Prior posts

 

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