Okay guys I've tried figuring this out on my own but I've had no success.

I have a 2006 Sentra Spec V with a VQ swap. I bought the car already completed and was told the engine came out of an 04 Nissan Quest and the ECU was from an 04 Altima. I later discovered the ECU was in fact NOT an 04 altima, but an 02 Maxima.
Every time I start my car it goes into limp mode, will not rev over 2500 RPMs. I then have to plug in a OBDII scanner and clear the codes before it will correct itself. I've checked the codes numerous times but do not see anything that would cause it be in limp mode.
Everything I've read and researched lead me to believe the MAF may be malfunctioning.
What is weird is that sometimes when I first start the car it will rev over 2500 but after I let off the throttle and try again it won't let me.
Now, if I wanted to, I could start the car and drive it without clearing the codes I just can't go over 2.5k rpms. Meaning it still seems to drive normal even though it is in limp mode.
I tried to provide as much back story and details as possible but if anybody has any other questions please comment.

 

My guess would be that the ECU is thinking you have a Maxima motor. Yes they are both 3.5's, but I'm thinking the Quest motor is slightly different to make it a practical SUV engine. I could be completely wrong though.

 

At this point I am even skeptical to believe the engine came out of a Quest. The guy I bought the car from seemed knowledgeable at first about the swap but now I've come to realize that he really didn't know anything about it.

 

No. That is not it. Absolute terrible advice. The only difference between the maxima and quest motors is the ECU settings, nothing is physically different.

That MAF would stop the car from revving beyond 2500rpm, go clean it and or change it and check its wiring. As for limp mode i would look into the knock sensor and harness. BUT you need to tell us what codes you are getting because there are quite a few different situations that can cause limp mode. Just saying limp mode is pointless, i mean a few bad coils can cause it, bad crank sensor, cam sensor, bad VTC solenoid. What codes were you throwing.

 

Again, do not listen to him. The Quest, Murano, Maxima, Altima all use technically the exact same engine until 2007 when they start having differences between the VQ35s. The only difference is the ECU settings, some are a little more aggressive others are not, all engines are technically identical, a common practice on here is to reflash the Maxima ECU with the 350Z settings. Because they have more aggressive timing. the only difference in a VQ35 in the 350Z and Maxima is the casting for the position of the motor mounts. Otherwise we would be using those too. As far as your ECUs, 02 maxima vs an 04 altima their is barely any difference in the ECUs, as long as your key works that what matters because the NATS system requires chipped keys which is a serious PITA to get around.

Your having issues with a sensor somewhere but you have to give more information then the car goes into limp mode. What codes is it throwing?

 

Don't need to be a ****, I'm learning. I'm offering my input to try and help him. I stated in my first response that I could be completely wrong...

 

Well the knock sensors aren't wired up but I have heard of at least one other vq swapped Sentra that isn't running knock sensors and I don't think his does the same thing.
These are the codes that are stored. And I was aware these codes would be present because I didn't wire the things to the ecm:
P1490 - Vacuum cut bypass valve
P0550 - P/S pressure switch
P0650 - MIL circuit
P1564 - ASCD Switch
P0462 - Fuel level sensor
P0444 - Evap canister
I should also mention that once I start the car and clear the OBD I can drive the car anywhere and it will not go into limp mode. It ONLY goes into limp mode upon initial crank.

 

No worries man.

 

Of those codes the vacuum cut and maybe the fuel level sensor can cause initional start up issues but I would clean or replace the MAF first, this things run 30 at the JY all day. or if you have a pick and pull/LKQ near you just pocket a few of them, if you get caught dont blame me. Some of those random codes you can go ahead and fix. For initial start up problems i would look into coolant temperature sensor. It could have gone bad or on its way out, but not enough to throw a code.

How is drive ability when cold, does it buck or sputter at all. Is it hard to start sometimes?

 

Please download the FSM for your ECU (04 altima?) and for your car.

Nicoclub.com/FSM


Your 2500 rpm limiter issue is related to the MIL circuit. code p0650

FAIL-SAFE MODE
ECM enters fail-safe mode when both DTC P0650 and another DTC, which calls for MIL to light up, are detected at the same time.

MIL circuit Engine speed will not rise more than 2,500 rpm due to the fuel cut.


Since your MIL circuit or CEL engine light is not working, soon as the ecu detects another fault code it limits rpm to 2500 rpm letting you know something is wrong.

 

I have the FSM somewhere on my phone. I had to reference it a lot when I was rebuilding my wiring harness. Didn't see anything about the MIL circuit causing limp mode but thank you for the knowledge. I pulled my UIM to clean the VTC solenoids and change my plugs so once i get it put back together I will add the MIL circuit back to the ECU and wire it to an indicator light.

 

Surra, just wanted to say thanks again for your knowledge. I went and bought one of those little "alarm led" indicator lamps from O'Reillys and wired the ground to terminal 33 (MIL circuit) and the power to terminal 43 (ignition switch) and no more limp mode!!! Such a feat. I love when things go my way lol.

 

Awesome! Glad you got it working!

 

Must be awesome

I wanted to do this to a Sentra but was too poor

 

They are actually pretty cheap to swap! All depends on how much time you spend looking for the engine. But I've seen VQ's go for as low as $600. My sentra is actually for sell if you're interested