Samuel Farrow

Hi guys, new member here and I've basically reached the point of turning to the internet for help. Quick heads up, this is a long one 😬😅.
Story goes, I blew the bottom end bearing on track and have now replaced the engine with another VQ35DE (non revup), the same as the old engine.

The engine is installed but it's being extremely temperamental getting it to run right.
Sometimes it's starts, runs ok (1200-1300 cold idle, 800 warm) but no acceleration.
Sometimes it's starts but has a very odd idle (goes between 200-1200rpm) with no acceleration.
Only recently a new problem occurred where it starts and dies practically immediately.

HERES WHAT I KNOW SO FAR:
- Engine codes P2127 and P2138 have occurred. After looking them up, swapped the throttle position sensor and calibrated it using ignition. No difference made, unsure if codes are still present but engine light is on still.
- Fuel pump DOES engage everytime I turn the key and smells EXTREMELY rich when it starts- Spark IS present under all cylinders. Thanks to a shiny new manifold (talk about later), it showed one of the cylinders not firing. Replaced coil from old engine and got rid of the problem.
- No fuses have been blown- Car recognises key- Exhaust has been replace with tubular decats. Only difference between the 2 manifolds (despite the obvious lack of cat material) the pre cat O2 sensor is now only picking up information from 1 cylinder instead of 3 cylinders due to the way they were designed (if this makes a difference)
- MAF sensor has been cleaned and ran on old engine but no air filter has been installed yet due to me having to cut down the MAF pipe for it to fit. If you know running without an air filter would cause drastic issues like I'm experiencing, let me know.
- crank and cam sensors are all connected.
- same ECU and has not been changed.
- can't hear a vacuum leak at all- throttle body has been swapped- all earth connections seem to be in place (if anyone knows any hidden ones I might have missed, let me know)

Here's what's been changed:
- as mentioned before, it's now a tubular decat manifold where the O2 sensor only gets information from 1 cylinder per side, not 3.
- spark plugs- thermostat
- O2 sensor wires have had to be extended due to O2 sensor hole location.
- will have cone filter but is running open intake pipe- some coils from the old engine I knew were working- throttle body has been swapped back and forth.

I think that's everything but if anyone who's swapped a VQ has any pointers to why it's running so rough. Let me know.

Cheers 👌
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bealljk

iTrader: (13)

I would automatically replace the crank shaft position sensor and the cam shaft position sensors with OEM nissan or Hitachi Brand sensor ONLY.

Youre saying this car / new engine has run for more than a few seconds / a few minutes.

Have you checked compression? Probably not a huge factor right now but it’s always good to check. Also I’d do a leak down test.

Did you do anything with timing with this new engine?

What about your APP Sensor - can you check that it’s working correctly?

What engine harness did you end up using when you did the swap?

Sundown72

Those codes point to the cabin side of the accelerator system. Did you replace the accelerator position sensor, or the throttle body/throttle position sensor?

Loose connections? Broken wires?

Stuck injectors? Failing fuel pump? Clogged fuel tank vent?

+1 for the crank position sensor, you should also do the cam position sensors as preventative maintenance when doing a swap. Rough running and cutting out can be a cam position issue as well, but usually throws a misfire code.