Infiniti G20 Nissan Primera Forum banner

Rough starting/ no idle after engine swap

2058 Views 21 Replies 7 Participants Last post by  ferrari21
Hey guys I finally got the engine in my 99 G20. When starting it has an extremely rough idle and often dies, but will smooth out if you rev the engine. Checked timing, spark, and fuel, all seem to be good. I'm suspecting vacuum leak/hose hooked up wrong but I dont have any good pictures of the connections. I downloaded the FSM and have consulted the diagrams with no luck so far. Any help would be greatly appreciated. Btw i swapped in another DE motor from a wrecked 02 G20.Thanks!
1 - 20 of 22 Posts
What did you use from the '02 motor? Pics?
Humm... 99 to 02 swap.. what all got swapped with it (harness, sensors, ecm)??
I used everything that was on the motor. I did not swap out the ECU between the cars. Unfortunatley Idont have access to the donor car anymore.I kept most of the parts off the old motor ( it had locked up due to a bad oil pump) Does anyone have pictures of the vacuum connections? I'll take pics of the car and motor tomorrow if I have time after work.
Sorry for the delay. I've been working crazy hours this week. I should be able to get some good pictures this weekend. Does anyone have pictures or advice for the vacuum connections?
there are a few stock under hood pics available on this site. not sure whos car i used when i was putting my p10 together, it was a merlot color.
Not sure if is the same but,usually when i swap a 2000 motor to a p10,or b13/b14 i swap the intake manifold from the 99 to 2000 motor.
i thought that 99-02 were the same? Correct me if im wrong, im just now starting to work on import vehicles.
Then engines are similar but not the same. Use the harness/sensors, intake and exhaust from the 99 motor.
Well crap. The other car is gone. I pulled the ps pump, egr, and a few other pieces off of it before it was junked. What specific items do I need to swap out?
harness/sensors, intake and exhaust from the 99 motor.blankman3 rite.
Is the intake G specific?If not what else did they come on? G20s are few and far between in KY. I know the harness is, not sure about the sensors.
Harness being G specific I mean....
Option 1) The best route for you to go is to modify your 99 harness for an older style 94-97 OBDII ECU. Then you can junk most of the emissions crap that came on the 98-99 Sentras/G20s. NO NEED FOR THE 99 MANIFOLD HERE IS WHAT I'M TRYING TO GET AT!
You can use all of the sensors from your 99 to run with a 94-97 B14/P10 Ecu, and keep the 2000+ roller rocker manifold.
This is by far the easiest and cheapest way to go when swapping a roller rocker motor into a 99.

Option 2) Swap the 99 intake manifold onto the roller rocker motor like recommended already. This is going to take a bit more time as the 99 intake manifold takes a bit of modification to fit on the 00+ engines (clearance issues with the throttle body, and coolant hose connections in the back don't quite line up), but you can sustain all the sensors and stock emissions crap from your 99. It can be done but it will be a bit more time consuming, and maybe even a bit more thinking to get through.

The reason I recommend option number 1 is because I hate the 98-99 sr20de emissions systems. They're a pain to work on and diagnose and they are over engineered, and unnecessary. Nissan made a big mistake with these engines, I think part of the reason they started producing the RR engine was to fix these issues. Good news is that it isn't very hard to fit a 94-97 ecu on a 98-99 sr20 car, a swap of a couple wires on the harness plug, and ripping out some unused emissions components and you're done!
See less See more
Thank you Ferrari! I'll call a couple junkyards in the A.M to see what I can dig up.
Btw, would any particular year (94-97)ECU be better than another?
One other question.... most of the sensors are from the 02 motor. If im going to swap ecu, what sensors do i need to pull and replace and what can i keep?
No. Not if i can help it. Ill swap the ecu.
As long as the plug matches your 99 plug and it is the same transmission (auto or manual) any 94-97 ecu should work. You will also use the distributor, all the sensors, injectors (may need to modify fuel rail slightly) and maf from your 99. You will simply only remove the emissions components no longer functional that were being used on you 99.

Common mistakes on swaps people make...
-fuel feed and return lines reversed
-open vacuum or pcv lines
-wrong maf/sensors for ecu or maf/sensors are not all connected
-low/missing fluids

Make sure you read through my thread. It explains a lot.
1 - 20 of 22 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.