I recently finished installing a 2003 Maxima VQ35/6spd into a 2003 Sentra.. The car starts/runs decently.. but it's down on power a good bit. It seems like in open loop, it's down more than in closed loop. I can partial throttle the car at low RPM, and it's got a good bit of pick-up.. but, as soon as I floor it, and it gets into open loop, you can feel the power drop off a good bit. At around 5K rpm or so, power comes back in.. It's not the variable intake piece opening up, either.. I tried zip-tieing it open, and the surge still comes in around 5K. The last car that I swapped.. had a LOT more power down low/midrange than this car does. I've checked/replaced the following

MAF sensor
Fuel pump
02 sensors
Plugs
Cleaned ECU/sensor grounds (on top of front bank cylinder head/timing cover)
Verified that the CVTC system is working
Verified that the VIAS solenoid/valve is working
Replaced knock sensor

I'm not sure what more I can check... The engine has no bottom end whatsoever.. it's a pig until about 5-5500rpm. Then it sorta takes off.. you can feel the power come in.. and then it sorta drops off about 2-300rpm before redline.

I have a few emissions related codes.. evap, swirl control valve and rear o2's.. Those shouldn't affect anything power-wise. I do have a CAN system code.. not sure if that would affect anything. It's wierd.. on this ECU/harness.. where there is supposed to be CAN lines (Pin 109 and 113), there's nothing at all.. Yet, I am throwing a code for the CAN system..

I have a AEM CAI and SSAutochrome 96-99 headers/y-pipe.. Still on the stock 2" exhaust..

Can anyone think of anything else to check?

Travis

 

Coilpacks?

 

Possibly... is there a way to test the coil packs?

 

Faulty coilpacks usually cause hesitation during acceleration (not sure if that's the exact problem you're describing). You can check them with an ohm-meter, I believe the spec of resistances can be found in the Haynes/FSM or I'm sure it's been posted on the .org somewhere.

 

This is more just a lack of power... it feels like the ECU is pulling a bunch of timing in the low end and midrange.. I'll check the coil packs though.. thanks!

Travis

 

Pulled the intake mani... coil packs and plugs... The plug hole closest to the TB on the rear bank had oil in it. It came up to the plug a bit.. not sure if it was enough to cause any problems. I will have to order a new rear valve cover, as I believe that the seal is incorporated into the valve cover. The plugs all looked fine, otherwise.. I did a compression test while I had the mani off. With a cold engine, I got 180-182psi consistently across all of the cylinders. I replaced the last coil pack that had oil in it.. just to be safe.. and I siliconed the crap out of the area around the seal until I can get a new valve cover. I'm letting the silicone dry and I'll take it for a spin in a few..

Travis

 

travis, have you finished brian's car yet? It has been a while huh?

 

Those are some odd codes you are getting.

Did your engine, transmission, ecu and harness all come from the same vehicle?

In 02/03, only the auto tranny cars had the partial CAN system.
There are no swirl control valves in the 3.5.

Do you have access to an OBD-II data logger to see what kind of timing you are getting at WOT?

 

What knock sensor did you replace with?

 

check the fuel pressure.

 

Are you using the stock returnless fuel system with the fixed regulator on the pump assembly?

Fuel pressure should be 51psi at idle.

 

I've been working on Brian's car for a long time.. I do whatever I can, as I am provided payment. Brian and I aren't saying anything about the car, as far as it's setup, until it's completed, with dyno numbers, track times/video's, etc.. Just trust me when I say that we're fixing to raise the stakes in the horsepower game.. BIG time..

Travis

 

Yeah.. it's wierd..

The engine, trans, ECU, harness, etc.. all came from a 2003 Maxima 6spd, SE, without traction control, and open diff. Clark (JWT) and I figured out, by looking at the guage cluster diagrams, that the water temp guage and tach are still analog.. and that there is no CAN system. Pin's 109 and 113, which should have a red and a blue wire.. have no wires/pins at all... just empty slots. I looked around on the harness, and couldn't find any other spiral wrapped red and blue wires, either.. Most of the time.. the CAN wires are wrapped together.

I'm going to get the Consult II this afternoon, and make some runs..

I am going to check the fuel pressure as well.. I am also going to hook up a AEM wideband.. which should help. Thanks for the suggestions/help guys..

Travis

 

Replaced with a 2003 Sentra SE-R knock sensor... same part number on both sensors..

 

Frosty's Name is Bryan. But that is fine.

2003 Maximas don't have CAN.

Did you get it working?

 

Sorry.. I always get "Brian" and "Bryan" confused..

I hooked up my AEM UEGO... It's reading 17.5:1 under load!! So, there's our power loss... I'm going to Autozone to buy a fuel pressure guage in a few minutes.. I'll also check the MAF voltage under load to see what it's reading..

Travis

 

Replace the stupid 1 foot long harness that goes to the knock sensor. Last summer I replaced my knock sensor because my car was suddenly slow and it didn't change a thing.

Then I replaced the knock sensor harness... and out of nowhere it went from running 14.30-14.40@98-99 mph to 13.70-13.80@104-105 mph. Believe me, that is VERY noticeable.

 

**** running that lean wow.

 

You're probably a return fuel setup that operates at 43psi vs. the VQ35 returnless that operates at ~51psi.

Add an AFPR or just toss in a Walbro GSS342.

 

The Sentra operates at the same 51psi of pressure as the Maxima.. Same dead-head system. I think something with the sending unit, or the pump, is suspect.. Or, the voltage to the pump is dropping out.. I'm going to test all of these theories this afternoon..

Travis

 

I'm thinking about just tossing in a 470K resistor at the ECU, between ground, and the KS pin. For some reason, these sensors are really sensative.. and pull timing for regular engine noise at times.

Travis

 

I know but wouldn't that worry you a little? Especially when it's 100 degrees outside this summer?

 

Nah.. 93 octane should be fine..

 

i called it

 

Well... you don't get the cookie JUST yet.. but, I'll let you know this evening..

 

Well... it's not the fuel pump... I hooked up a test guage to the line, and stuck it to my windshield.. it's reading between 50-52psi of pressure, at any given RPM/load. So, any other suggestions as to what would cause this car to go dead lean?

Travis

 

Think I've found the problem... The Maxima ECU apparently uses a different flow meter than the Sentra/Altima does... SO, I'm going to be ordering a MAF sensor on Monday..

 

Not to the driver information system or the data port. But A33Bs do have a CAN connection to the TCM, TCS, ABS and VDC.

Page EL-429+ on the current 2k2 ESM.

 

And what's messed up... is that when you read the pinout, there isn't a side-note, or anything, saying that you may or may not have CAN lines, depending on the trim of the vehicle.. I mean, I figured it out eventually.. but, usually, they'll put a side-note or something if there's an exception.

 

The entire harness is identified in the ESM. And I have donated my entire '94-'05 Nissan/Infiniti ESM collection to www.phatg20.net for everyone to DL for free. When Nissan finally releases the final two '06 books (Z, Murano) I might give him that collection too.

 

When I look at the 2003 Maxima EC section... the wiring schematic shows pins 109 and 113 as CAN lines.. Now, I realize that some vehicles don't have some components (Automatic control module, etc..), but, it usually says something about it on the side.. or, they'll show a unshaded circle in the splice.. which means that it's optional.

I mean, it's not THAT big of a deal.. but, it was sorta confusing for a while, trying to figure out what was going on. Then, in the wiring pinout detail list.. there's no output pin for the water temp guage on the dash.. since it's still analog, and not on the CAN system. Just little stupid stuff that's more annoying than anything else.

 

what was the problem? did you find the culprit? maf sensor?

 

Yeah.. turns out.. the Maxima and Sentra/Altima MAF's are different.. I assumed that they were the same. I found that the MAF voltage was a little low.. and after seeing 17.5:1 with a wideband, I figured out the problem. Found a MAF in the junk yard.. and all is well..

Travis